E-Bodies.org Cuda Challenger Forum

Enjoying a whiskey right now. I've been planning and pondering about how my new A66 chally would do in the quarter. It is a scat pack car, ya know. :)

Not daring to touch the engine (runs superb) for quite a long time, but I'm curious what I should expect my quarter mile time to be if I took it out to the local strip with street radials as-is, bone stock with large valve J heads. 3.23 gearing, 727, solid compression.

Quarter mile time stock I would assume 14.5 ish?

My future plans are very light touch. 268 cam with stiffer springs, 2.5 TTI exhaust w/ x-pipe, stock manifolds, stock AVS carb, RPM air gap (orange), 3.55 SureGrip, and that's it friggen it. Rejetting and tunning of course. Quarter mile then would be?

I would guess low 15's.

The 3.55's will help, but 3.23 will be hard to get in the mid 14's on a stock set up.

I agree with Cody. 340's like to rev so I see it in the 15's with the 3.23.

Most car tests of the day put the 340 automatic 1970 Challenger in the mid to low 15 second quarter miles.  T/A's w the 6pk typically came in the mid 14's w the 3:55 gears and 4 speeds.

I have an A66 Challenger automatic convertible (a little heavier then the hardtop) I tested the car at Raceway Park (Englishtown) back in the 1980 and was getting times in the high 15's w 3:55 gears, 70k miles on the car, minimal fine tuning and stock AVS carb.

The 340 Challengers in some cases tested out just as quick as the heavier 383 Challenger RT's or just a bit quicker depending on gearing and transmissions.  340's in the lighter a bodies were even quicker.
:stayinlane:

Yes: The 340's liked the lighter A bodies, especially with a 4 speed and 3.91's.

https://www.youtube.com/watch?v=JNxY3XEXC2k

The Cuda I am working on did high 13's with 3.55 gears in the late 80's.. 340 4 speed, headman headers, purple shaft cam don't recall the grind but not terribly radicle.. that was it..

I though "Scat Pack" vehicles had to hit high 14s or better...Perhaps the A66 only hit high 14s with 3.55 gearing...

See attached. That shows the A66 car w/ 4 speed (probably taller gears and sure grip?) running 14.5. It seems like I'm honestly just a 3.55 rear-end swap away from 14s. 3.55 because I don't want to break the road-tripability of the car.

My friend's 1968 Barracuda 340 4-speed runs a 14.9 up here at 2800ft elevation, which translates to mid 14s at sea level. Bone stock aside from some suspension mods and street radial tires. Well, it DOES have 3.73 gears, though.

Thanks ledphoot...high 13's sounds good.

My goal is mid 13s. That's "fast enough" and I think it's obtainable by still keeping the car look very stock-ish.

Do you guys think with my mild performance upgrades that I mentioned in my first post that mid 13s on a good day at sea-level should be possible? I may add TTI headers if needed, but I do like the looks of manifolds. :)

A 68 Barracuda is about 500lbs lighter than a Challenger which equates to .5 in the 1/4 mile. You can make 13's no problem with your Challenger. with a cam swap and some exhaust work. Personally I would leave the stock intake manifold and change the carburetor though. The stock 340 intakes were really good pieces.

You are a long way from 13.99. You will need to improve airflow in and out of the engine. You will see reasonable gains from gearing, and you will need a better torque convertor and a shift kit in the transmission. Every tenth you pickup makes the next tenth doubly hard...

Wait, 500 lbs? That seems a bit extreme. His car comes in at 3250lbs.

Do our an a66s really weigh 3750?

I have a 73 challenger with the 340 and 391 gears 727 manual valve body built to 1970 specs some minor upgrades triple angle valve job bigger carburetor it ran a 14.1at 98 miles an hour. But we had a stock ECU in it. It fell flat on its face off the line I think we could've done a few tenths better than that that was in 1990 and I never went back

340's definitely need a 4 speed and 3.91's to run any kind of number. They need to stay in the power band and that's in the upper rpm range. Automatics don't allow you to leave at higher rpm's so your stuck waiting for it to really start coming on. The 4 speed keeps the rpm's closer with 3.91's so you can stay in the power band for the whole run. I have seen and owned many 340's that ran great with that combination. Take that same motor and put it a car with a automatic and tall gears and it turns into a pig.

I recall hearing Fremont Drag racers mention the 10:1 Rule of Thumb for muscle cars in the 70's.

Removing 10 lbs of weight on a car with a 10:1 weight ratio will increase acceleration by the same amount that one or more hp would in the quarter mile.

Agreed, very simply put and other considerations have been made like gearing, light flywheel, wheel diameter, traction, transmission, etc

Stock 70's Challengers need to lose some weight!!  Fiberglass hood, alum heads and intake, alloy wheels, different battery, etc

I can't speak for automatics, all of my mopars have been 4-speeds.. To get the most out of your engine you're going to want headers, the stock manifolds suck. You may want an intake and you definitely need a properly tuned carb (or EFI).. Those things combined with a good cam that will work with your 3.55 gears should get you in to the 13's if you can hook it up, so don't forget tires :) The gears / cams / torque converter should be selected to work together.

Cam
http://www.hughesengines.com/Index/products.php?browse=category&level0=QS0gU21hbGwgQmxvY2sgIkxBIg==&level1=Q2Ftc2hhZnQ=&level2=RmxhdCBUYXBwZXQsIEh5ZHJhdWxpYw==&level3=U3RyZWV0L1N0cmlw&partid=30241

or this one if you want a milder idle

http://www.hughesengines.com/Index/products.php?browse=category&level0=QS0gU21hbGwgQmxvY2sgIkxBIg==&level1=Q2Ftc2hhZnQ=&level2=RmxhdCBUYXBwZXQsIEh5ZHJhdWxpYw==&level3=U3RyZWV0L1N0cmlw&partid=30239

Stall
http://www.manciniracing.com/tcibrtoco.html

Shift Kit
http://www.manciniracing.com/19tor904witv1.html

Intake
http://www.manciniracing.com/rpmairgapman.html

Carb
http://www.manciniracing.com/decastdeca2.html

Headers
http://www.manciniracing.com/smblshepocec3.html

And in the end if the slush box really is holding you back that much you can always make the car a stick :) There is nothing like shifting a pistol grip Mopar.. Nothing.

Really appreciate this guys. Id like to do a little bit at a time.

My thought is to start with transmission first because it has a shift shaft leak.

There's a really good mopar tranny shop here.

I'm planning to drop it by him, have him replace fluid and seal. I can also have him install a shift kit. That will take care of the tranny for awhile until it's time to mess with the stall. Is that B&M that was linked the shift kit of choice?

I remember installing a shift kit in my ford galaxie. I don't remember that there were any negatives to drivability doing so.

Paul Goldsmith tested an early 1970 Challenger 340-4 speed car in late summer 1969.
This was prior to the formal release of the formal A66 package (flat hood w V-8 emblems on the fenders)
The test Challenger had a 4 speed and 3.90 gears.  As per Paul: 0-60 mph in under 7 seconds and 1/4 mile in the "14 second bracket" (his words)

This was an early totally stock Challenger

The 4 speed and lower gearing really livens up the Challenger!

I posted the article in a post here a while back.

Curb weight:1970 Dodge Challenger 340 V-8 4-speed (man. 4 speed) (without a driver) 3351 lbs

I've never had an automatic 340. I would suspect that really tying the camshaft and converter choice together would be pretty important.

Well, I made my first decision today that was biased towards performance vs "oh my god must be 100% original!". Probably will piss some off. But hear me out, because I can make the argument.

I decided to go with Aftermarket Alloy Magnum 500 rims vs Aftermarket Rallye steelies. Runcharger really helped me make this long and annoying decision. If Runcharger is correct that rallye's weigh 30lb a wheel, then these Alloys will give me a 56lb less weight total for the wheels. That's very serious...50lb in unsprung weight is equivalent to 200lbs being dropped off the car.

Whether or not that matters now irrelevant, but it may matter when I'm trying to get comfortably in the 13s. :)

It was definitely the right decision. Challengers with Magnums look very good too! I wasn't getting any responses from US Wheel or Wheel Vintiques from email nor their Facebook page. I've read some quality issues related to run-outs. And the trim-rings not fitting all the way in would kinda suck. Maybe they have a trim ring that solves that, maybe the don't, but not getting back to your customer for these questions is pretty asinine! Maybe I "had" to go to 4.50 backspace in order to alleviate the trim ring gap, maybe I didn't. But one thing I can say, the Magnums have the stock factory 4.25 back spacing and look GREAT while the aftermarket rallyes is largely an "unknown" at that back spacing for trim ring fitment.

Oh yea, and the alloys costed me $140 less than the steelies! Dead serious!

So yes everyone, I made my first performance-biased decision on the Challenger today! Truth is, NEITHER wheel is original to the car. So it doesn't matter in actuality. I'm always going to keep the 14 Rallyes that came on the car. THAT is the original wheel that stays with the car.

But for now, and for the long term, I chose the lighter, cheaper, better material, and "nicer" wheel in my opinion. Charlie gave me the nod of approval. :)

My challenger will have magnum feet as it runs down the street and strip. :)

I also ordered Mickey Thompson Sportsman S/T RWL 235 radials all-around. While all radials are pretty much the same as far as traction is concerned (aka "not good") I believe these get the "slight" nod for stickiness over the rest.

Keep in mind, I'm going from Bias Plys....I cannot WAIT for radials. Tired of the car feeling like it's on ice skates. :)

First of all, you don't have to justify your decisions to anyone. It's your car, do what you want. If it pisses somebody off that's their problem, not yours. Personally, I like the Magnum rims. I have the original 14' ones for my 74 Challenger, but not on the car.

If you're needing traction you could easily go with a wider tire on the back than a 235.  :alan2cents:

This has been a great thread. Curious on some of your expertise. Please challenge some of my assertions/notions.

* I'd love to weigh my 340 Challenger. From everything I've gathered, the 68 cuda should weigh about 3,100lbs. So maybe the A66 challenger is 3600lbs! The only way to know for sure is to weigh it!

* I've read reports of simply throwing on a larger carb on a 340 without ANY other modifications is an easy gain. There's a couple magazine articles that I can link to that show this. Is this common knowledge or a myth?

* Being that you guys know my "end-game" plans, I'd like to know what make sense to do first, second, third. I'm certainly not going to do everything all at once. For example, does swapping on a RPM Air Gap Intake (yes, even though factory intake was good for it's time, the Air Gap is still much improved for the 340), does it screw over anything else, or will it not really do much until I continue to improve? Will it require tuning because the engine will become a bit leaner?

It seems like a mild shift kit and rear-end gearing are easily the first things that can be done without any worries with tuning or drivability. I'm really curious to get your guys take on what my gear ratio should be. From what I've been reading, some think 3.55 is a nice compromise for all-around driving and strip, while others with first-hand experience think it has to be 3.73, no less. I suppose the only way for me to know is drive my Challenger 65 MPH as-is for a good while, then use an RPM calculator to figure out what the RPMs would be and figure out if my short-road trips that I'd like to do are going to be a nuisance. Currently, it says that with 3.55 gears, I would be pushing 3,000 RPM at 65 MPH. Seems like 3.55 should be the max!

Second could be the exhaust system using stock manifolds. I just patched my original mufflers to buy me some time before I have to worry about it, but I do plan on a 2.5" TTI exhaust with some good mufflers (torn between Ultra Flows, Super Turbos, or Magnaflows) that will allow that "Dodge" tone to come through without waking up the neighbors. I even want my exhaust to sound authentic and "close" to stock, but wouldn't mind ~20% louder...

From there, you're left with cam and upgraded valve springs, intake, carb (is it necessary?), headers (is it necessary?), and torque converter. At this point, which are required to do at the same time? Do you guys think it's going to take everything to get into the 13s?

The older and older I get, the more I become like my pops. You have to find the right balance between drivability, original, and fun. I'm hoping this balance can achieved landing comfortably in the 13s.

I can tell you that my car does pull pretty good and doesn't feel slow...it's nice to be behind a V8 vehicle again. It doesn't pull as hard as my friend's stock 68' Barracuda w/ 4-speed and 3.73, but it doesn't feel far off. Again, he runs 14.88 up here at 2700 elevation, which is pretty respectable I would think. I do understand that the 4-speed would really help vs a slush box, but for me that's passing the boundaries of "keep it original". Maybe in 20 years...but definitely want to really enjoy and treasure the 727.

I am the wrong guy to be talking to with regards to originality.I love the style of these cars, the way they drive, the performance and tweaking them. I am the third owner of the Cuda and I have done a lot of things to the car that a lot of people will disagree with. I enjoy messing with my car, it's my "Hot Rod" not a restoration project or a "Collectible", I am going to drive and enjoy this car so I am building it how I see fit.

If you want to keep your car stock or even mostly stock, that doesn't jive well with shaving 1.5 seconds off its quarter mile time. It means doing intake / headers / cam etc. You can do these things and keep them fairly low key... In the end it's your car and do what makes YOU happy.

When it comes to the gearing and automatic.. You could go with a cam like the larger of the two I suggested and change your gear to 3.73's (or better yet 3.91's) and put a Gear Vendors Overdrive on your transmission. That'll give you the highway manners you desire and the lower gears to keep the 340 in it's power band at the track.

Quote from: kawahonda on July 20, 2018, 09:39:06 PM
I though "Scat Pack" vehicles had to hit high 14s or better...Perhaps the A66 only hit high 14s with 3.55 gearing...

See attached. That shows the A66 car w/ 4 speed (probably taller gears and sure grip?) running 14.5. It seems like I'm honestly just a 3.55 rear-end swap away from 14s. 3.55 because I don't want to break the road-tripability of the car.

My friend's 1968 Barracuda 340 4-speed runs a 14.9 up here at 2800ft elevation, which translates to mid 14s at sea level. Bone stock aside from some suspension mods and street radial tires. Well, it DOES have 3.73 gears, though.

Thanks ledphoot...high 13's sounds good.

My goal is mid 13s. That's "fast enough" and I think it's obtainable by still keeping the car look very stock-ish.

Do you guys think with my mild performance upgrades that I mentioned in my first post that mid 13s on a good day at sea-level should be possible? I may add TTI headers if needed, but I do like the looks of manifolds. :)

Scat Pak and Rapid Transit (Plymouth) cars were indeed supposed to hit 14s. However, as you see, it was usually a special model with a select set of options and usually highly tuned by the factory engineers run under very good ambient conditions. They then associated those options with a select numbers of cars that were similarly optioned and they joined the club. Each car was not individually tested for compliance.

Mid 13s in a stock appearing package is certainly achievable, but you would have to get into the engine, trans, and rear end to do it.  This is why OD transmissions are so popular. They allow the numerically higher gear sets to allow a good run while allowing easy cruising.

I'd imagine over the winter I'm going to need to pull my intake in order to solve a water leak. I cannot find the leak, but I do know that it is a) dripping from bell housing, b) not coming from any of the freeze plugs or lines, and c) coming from back driver's side of engine near dizzy. It will drip about a cup every 2 weeks.

If I'm going to be pulling the intake, I might as well go ahead and pull the heads to figure out what size valves my J heads have. Get everything cleaned up. At this point, I have some options:

1) Clean, paint, check/machine heads (increase them to 2.02 if not already) and put everything back.

2) Clean, paint, check/machine heads (increase them to 2.02 if not already) and install RPM Air gap intake (paint orange) and put everything back.

3) Clean, paint, check/machine heads (increase them to 2.02 if not already) and install RPM Air gap intake (paint orange), install an aluminum water pump (paint orange) and put everything back.

4) Clean, paint, check/machine heads (increase them to 2.02 if not already) and install RPM Air gap intake (paint orange), install an aluminum water pump (paint orange), install cam and springs and put everything back.

I'm thinking 4) currently at this point for the "do it once, do it right" perspective, but I have questions:

1) Is it a must from a drive-ability perspective to replace the torque converter immediately when a new cam goes in?

2) Will replacing the intake only (option 2) require rejetting on the carb, or screw anything else up?


Assuming from an originality perspective, if I keep my original cam/springs and my original intake in a box then it won't detract much. Infact, I'd like to restore the original intake (get it bead blasted and painted).

The cam should be selected with the compression, vehicle weight, octane, street/strip use, and several other factors including the torque converter taken into consideration for best results/drive-ability. 
The new intake would likely benefit from a re-tune of the carb for optimal results.  Maybe timing too.

You can always throw parts into the engine bay and the car will run.  But selecting the parts to work together or being able to tune them to do so is where the difference is made.  I don't know enough to select a cam by myself and expect to hit it the first time so I'm planning on getting help from the engine builder and forums.  The cam suppliers can be helpful in selection too.

Just about any camshaft change or intake swap is going to give you less low end torque than you have now. So I bet that 340 is pretty slow out of the gate right now and it will only be worse with a camshaft or intake manifold change. That's why I think a properly chosen torq convertor and maybe gearset is just as important as a new camshaft.

Assuming stock pistons you should in theory have pistons standing .018 proud of the deck....  in reality they'll be .008-.018 proud....

J heads typically cc around 72cc Blah Blah Blah.... If you want I'll type it all out... But at the end of the day I'd cut the heads .030 on the chamber side & .028 on the intake side..... After that try fitting the intake, in theory you need to cut the end rails on the intake about .040 but usually the original gap is .070+ so by eliminating the cork end seal & using silicone you don't need to cut the ends...... That will put your true compression ratio at about 9.6-1 which is perfect if you have decent (by today's standards) fuel available.... 

I thought the 68-71 340 motor was already 10:1 or 10.5:1 compression??  The72 and later with the cast crank were lower compression, no?

I found several references that indicate this.   
"To meet 1972 model-year emissions rules, the 340 was detuned; the compression was dropped to 8.5:1, and the intake valves were smaller. "

If he truly has a 70 motor with those pistons, cutting the heads may not be the way to go.

The 10.5 is advertised and was not accurate. Real, as manufactured compression ratios were usually at least 1 point lower than advertised.

In whichever case, I definitely have a high compression motor already. Not sure why I should cut/trim anything. J and H heads did not differ in the CC volumes (at least that's what all sources are saying). I do have a date-matching motor from '69.

Aside from sending my distributor off for re-curving, I'm still not sure what all I should accomplish.

Pulling an intake I assume is a pretty semi-big ordeal (not THAT big). I will HAVE to do that, no question about it. My thought is why not just pull the heads off at that point and get them checked out (and figure out what my valves are). Maybe my water leak is coming from my heads...hard to say. Another good reason to pull them, clean them up (and paint them, they are blue), and reinstall it.

I know for sure that a cam will have to be carefully selected...certainly not by me either. I need to rely on someone that knows 340 auto challengers and knows what I'm after, which is a stock sleeper look, can touch in the 13s, but retain all manner of drivability.

I'd love to just do my rear end gearing this winter instead of engine (go to 3.55 or 3.73), but the water leak is driving the need to tear down the top-end.

Quote from: kawahonda on September 20, 2018, 08:23:04 AM
My goal is mid 13s. That's "fast enough" and I think it's obtainable by still keeping the car look very stock-ish.

Quote from: kawahonda on September 20, 2018, 08:23:04 AM
In whichever case, I definitely have a high compression motor already. Not sure why I should cut/trim anything. J and H heads did not differ in the CC volumes

Cutting the heads is gonna get you closer to the high compression you think you have.....  Advertised compression ratios from back in the day are no where near true measured compression ratios.....

Advertised C/R on a 340 is 10.5-1....  Measured is around 9.0 maybe 9.1-1

Milling the heads while they are off is relatively cheap & easy.......

Back in the day the way to make these cars really run was to "Blueprint" the engine, a big part of that was getting the compression ratio right at that advertised number..... NHRA specs for the J head have the chamber volume at 60cc when in reality stock they are 72cc..... Cutting the head .030 will reduce chamber volume about 5-6cc...... 

You do whatever you want, just trying to offer some tried & proven advise...

Always accepted Randy and will be asking for lots of advice from you. Just wanted to state that from my understanding, J and X heads did not differ in CCs. Getting either of them higher is something worth doing...as long as 91 Octane is still preserved.

It's true J & X have the same chamber volume & virtually the same ports, some even have the same valve sizes... And if they don't it's an easy upgrade... A little blending of the bowl at the same time would be a bonus.....   Little touches are how you reach your 13.5 goal & make it look stock.....  Well hiding a 414 in place of the 340 is another (easier) way....

Sweet. I'll look into all those things when the heads come off. Good information.

Cam and Intake I still think make the best sense to do during that time, rather than bolting it all back together and doing it again in the future.

The Air Gap intake once painted orange should look very close to stock (at least passes my definition), so I think that's a given.

I think the cam selection is going to be the one that I need to use as much help as I could on. What cam works OK with a stock converter and 3.23 gears and works great with higher stall converter and 3.55 or 3.73 gears is what I think I should be after, with 3.73 as the "default" choice at this point.

Distributor will be re-curved this winter. I'm told that a re-curved distributor should work well stock and it should work very well with the planned mild upgrades, so no reason to wait on it.

AdvancedDistributors wants quite a bit to recurve the distributor. My buddy on the east coast is not really a good "buddy" so I may be shopping around for other places that does recurving. For sure, my vacuum advance needs to be reduced, which means replacing the canister for my model. I've decided to run mid 13s on the single point dizzy...

I've also read tales that it was a very popular thing in the 70s to bolt on a Carter AVS from a 383 or a 440 to a 340. The 340's seemed to love the increased CFMs, even in stock form...

I have a 73 Cuda, 100,000 miles, torker single plane manifold and FAST EFI, TTI headers, 727 shift kit'd and Dana 3.74 rear, 295 street tires.
I shift at 5200 cause the old valve springs just won't let me past that point, at just above sea level I'm at 14.81-14.85———- all day long no matter what I do. Don't need to do burnouts just drive round the water box, give the tires a quick hit to clean them off, up to the beam and proceed.

Here's what I'm thinking. Keeping in mind that "Phase 1" (whatever that means) has to happen over the winter to solve water leak.

Quote from: 1 Wild R/T on September 20, 2018, 09:28:52 AM

Advertised C/R on a 340 is 10.5-1....  Measured is around 9.0 maybe 9.1-1

Huh, I heard that the rating was optimistic, but that is a significant difference.

Who-da thunk you couldn't trust the specs from the marketing department??  :headbang:

Quote from: Crash520 on September 20, 2018, 01:21:38 PM
I have a 73 Cuda, 100,000 miles, torker single plane manifold and FAST EFI, TTI headers, 727 shift kit’d and Dana 3.74 rear, 295 street tires.
I shift at 5200 cause the old valve springs just won’t let me past that point, at just above sea level I’m at 14.81-14.85———- all day long no matter what I do. Don’t need to do burnouts just drive round the water box, give the tires a quick hit to clean them off, up to the beam and proceed.

Thanks for posting real-world numbers. Anything else you can say about the car? Does it still have heavy reinforcement items (bumpers, etc)? What's the timing set at? With a very mild 340 and 3.74 rear, I'd expect something more around low 14s, maybe mid 14s at worse at sea level with the rear end gearing that you have!

Quote from: gzig5 on September 20, 2018, 04:42:56 PM

Quote from: 1 Wild R/T on September 20, 2018, 09:28:52 AM

Advertised C/R on a 340 is 10.5-1....  Measured is around 9.0 maybe 9.1-1

Huh, I heard that the rating was optimistic, but that is a significant difference.

Who-da thunk you couldn't trust the specs from the marketing department??  :headbang:

You have to remember tolerances effect those numbers so nothing is etched in stone. Most of the time it has to do with deck height of the block and that's where it will lose or gain compression on factory built motors. That's also why when you ride in or drive identical cars and one runs like a scalded dog and one was a pig. 9 out of 10 times it's due to compression related to the block deck height. 383's are horrible about this issue.

Quote from: Shane Kelley on September 21, 2018, 07:51:02 AM
383's are horrible about this issue.

:iagree:  But all the engines of the time frame suffer from it... And Mopar's may be the worst...

Mine is bored .060 with a Lunati cam, 650 Edelbrock, TTI headers and 3.23 gears. I took it to track shortly after I got it. There was a rev limiter on it and I was hitting max speed before I got to the line. I clocked 14.7s three times in a row.

What was your MPH at the finished?

I'm a noob, but I'm assuming that you mean that you hit your top speed before crossing the end? I don't get how that's possible with 3.23 gears! In your case, going to a shorter gear would slow you down in the 1/4. I was always under the assumption (especially after looking at road tests) that 3.91s is what's needed to optimize the 340 Challenger Auto to get down the track in the quickest amount of time without running out of headroom. Are you saying that the 3.23 gearing with your car is running out of headroom?

The most I could get was 92-93. I was bouncing off the rev limiter so I couldn't gain any more speed and I was doing that before i crossed the line. I don't know where the limiter was set and my dash tach ran way high so I don't know what I was revving. After that I threw out the two coils that were on it, one Jacobsen and one Mallory. There was a switch on the inner fender to select which on, weird set-up, and I put on a Rev-n-ator ecu and Blaster 2 coil. Also added an after market tach so I could see what I was revving. I've never gone back to the track but I should some day.

Yea, I'd say something was seriously slowing you down on that day. Supposedly, 1/4 mile trap speed is a pretty accurate indicator of horsepower, given you know your "race" weight.

For sake of argument, let's consider that your race weight is 3800lbs and you were banging 92.2MPH trap speed consistently. That equates to about 200 flywheel horsepower. So yea, you were pretty much 66% of what your car should have done.

A 3800 "race weight" and 300 flywheel horsepower (what these had stock) should give a 105 MPH trap speed.

Wanted to ask you guys about rear-ends.

I understand that dr. diff sells complete sets with the Eaten clutch-less posi for about $1500. Do I know if I need the 7290 or the 1350 U-Bolt? I'm assuming that I have the OEM Mopar Adjustable tapered roller wheel bearings.

I'm wondering if there's other options that are easier on the pocket book, like perhaps a used drop-out. What specs are I'm going to want to look for if considering this route for a my 70 Challenger?

Still determining on 3.73 or 3.91. I've already thought through that this car may never really see much of the interstate, and the furthest I'd take it is probably an hour away, highway driving.

People these days are soft.... You've got a 340, they like RPM's so give it more gear & enjoy the fun....  Back in the 80's I drove a 440-6 Challenger with 4:10 gears from central California to San Diego & back.... Only thing it hurt was my wallet.... 

Running a 340 I wouldn't hesitate to use 3:91's or even 4:10's..... Maybe even 4:30's (I used 4:30's in my brothers Edelbrock headed 340 Challenger.....  But I also used a 518 trans....

Want an example of what lots of gear drives like? You have 3:23's now right?   Take it out on the highway rolling along at 65ish & drop it in 2nd gear.... 3.23 x 1.45 = 4.68.... Yeah, 4.68 gears.... Your 340 should be fine driving in second gear for an hour.... 

I have a 340 and a 727 and 355's seem great for the highway and mostly in town driving. 391's sound more fun. I bought a used 741 or 742 (I forget) case with nice used 355s, all new bearings and a new dr diff sure grip for $800 total.  Isnt Dr Diff in MT?  Maybe you can make the drive to save on shipping. 

I think the 3.91's are pretty streetable with a 340 as well.

I don't think I'd want to go any higher than 3.91. That's even a stretch I think, but I'll keep my 3.23's for if the need to ever "drive it far and away" comes up. even 3.23 is not all that of a tall gear.

Let's say 65 MPH is going to be a good cruising limit to dial everything in. Car shouldn't see it often, but that's a good speed to keep it highway-able.

w/ 3.23 and 26.1 OD tires, at 65 MPH I will be pushing 2700 RPM.

w/ 3.73 and 26.1 OD tires, at 65 MPH I will be pushing 3120 RPM.

w/ 3.91 and 26.1 OD tires, at 65 MPH I will be pushing 3275 RPM.

I wonder if 3.73 would also be a good option? My current case is a 489 case. I suppose if I were going the "used" route, than any 489 case will do? The nice thing about doing a center section swap is that it would be a good time to repack my wheel bearings.

Regardign ratios, EL5DEMON340 had a really good post that gives some guidelines. It's the best I've seen:

Daily driver and lots of highway = 2.96, 3.23, 3.55
Weekend cruiser with a good amount of highway = 3.55, 3.73
Weekend cruiser or daily with very little highway= 3.55, 3.73, 3.91
Weekend cruiser or daily with no highway and short trip= 4.11, 4.30, 4.56, 4.88, 5.13

I ran 4.56 on the street and they are a bit of a bear. They blow the tires off without effort and on a 100 mile highway trip they keep your speed down to around 60MPH and it isn't all that fun.

I feel that 3.73s may be the ticket. 3.91s may be close to 3.73 gearing for people with a 28" tall tire, but since I'll be running 26.1" for quite some time....MAYBE slightly bigger in the future...I have questions that 3.91 may be a little too short in my case.

3.73 SHOULD keep your highway driving "acceptable" but not "great". It gives you good potential (I think) at the strip. And it provides the standard "two-step up to feel a difference" where it's worth the cost to do it.

My friend's 68 'Cuda  340 4-speed has 3.91s and while he loves it for the strip, he said he's annoyed with it after often, but short highway usage. He drive's it about 10 miles into work most days of the week in 55-65MPH speed zones, and he's had that gear set for 10 years. He's worn down by it and wants to put 3.55s in.

He did say that I would likely be "OK" with 3.91s if I want to drive it on short highway trips (up to an hour away) once in a long while. The question is, if I'm already set on 3.73, is 3.91s that much worse? Looks to be 155 RPM worse...which seems like "not much".

Does going to 3.73 to at least give it somewhat of some highway manners close me out from hitting solidly in the 13s compared to 3.91 is the question....

How about you have some 28" tall street tires and some 24" tall race tires. Two pairs of tires and a couple steel rims are mucho cheaper than gear replacements or purchasing a second 3rd member.

HP2: The reason is that it breaks the "looks" department for me. Most of the time, I want it to look like a stocker. Having 28" tires on the back to me looks a bit hideous.....and I'd also have to get another set of rims that are at least 8". Right now I have 7" rims all around and 235's all around. The max I'd want to go on my rear 7" rims are 245, and that's only going to buy me .5" taller which doesn't do much to the RPM calculator.

I see your point though and totally get it and that's just a "way" to do it. I'd rather try to go as universal as possible and not have to "swap" out stuff.

I need a second 3rd member anyways. 3.23 gears are stinky for an auto, and it's an open rear end. Still going to need a new third member.

I'm more and more thinking that 3.73 would be a nice set for what I'm after.

Quote from: HP2 on September 26, 2018, 09:42:05 AM
How about you have some 28" tall street tires and some 24" tall race tires. Two pairs of tires and a couple steel rims are mucho cheaper than gear replacements or purchasing a second 3rd member.

That's simple and smart, tall tires for travel, small for short trips and around town fun! Good thinking right there. :bigthumb:

Quote from: kawahonda on September 26, 2018, 10:10:45 AM
HP2: The reason is that it breaks the "looks" department for me. Most of the time, I want it to look like a stocker. Having 28" tires on the back to me looks a bit hideous.....and I'd also have to get another set of rims that are at least 8". Right now I have 7" rims all around and 235's all around. The max I'd want to go on my rear 7" rims are 245, and that's only going to buy me .5" taller which doesn't do much to the RPM calculator.

I see your point though and totally get it and that's just a "way" to do it. I'd rather try to go as universal as possible and not have to "swap" out stuff.

I need a second 3rd member anyways. 3.23 gears are stinky for an auto, and it's an open rear end. Still going to need a new third member.

I'm more and more thinking that 3.73 would be a nice set for what I'm after.

Different strokes. Just throwing out ideas for consideration. Ultimately, its your ride and your wallet, so you have to do what makes you happy.

Yep still has factory bumpers, I do have an AAR hood on it.
I can't get it to rev past 5300 due to valve float, it has cupped seats and bad guides, trans has a shift kit installed, I have a D60 from a truck so have fitted Caltrac bars to control spring wind up.
I'm using FAST XFI SPORTSMAN EFI, so that controls timing which is around 32*. It's a tired motor and I haven't had a lot of time to really dial in the EFI

Do you guys know if my Challenger has the 7290 U-Bolt or the 1350 U-Bolt?

Quote from: kawahonda on October 08, 2018, 08:14:20 PM
Do you guys know if my Challenger has the 7290 U-Bolt or the 1350 U-Bolt?

Do you mean u-joint ?   7260-7290 ?

Not sure. Dr. Diff requires you to select either or before ordering a chunk.

Pretty sure I have the factory OEM tapered wheel bearings (not the green ones). But yes, I am required to select  7290 U-Bolt or 1350 U-Bolt for the pinion yoke option.

It should be a 7290 if still factory. I always measure them to be sure.

How would I go about measuring? Very highly sure it is still factory....this car hasn't been touched much.

It won't have a 1350.... It might have a 7290.... But some 340's had 7260's...  Back around 82 my buddy bought a pair of Lakewood high nickel content 7290's for his 4spd T/A.... Only to find it had 7260's.... So I got a great deal on a pair of high quality U joints....

And as far as telling which is which....

   You are choosing the size of the pinion yoke. I believe Dr. Diff uses a U-bolt to secure 7260 or 7290 U-joint to yoke. Instead of straps and bolts that screw into the yoke, It's a U-bolt that slides thru the yoke & nuts are screwed onto The U-bolt from the backside of yoke.  Not OEM, but stronger. I would order the large 7290 even if i had 7260 drive line. They make U-joints that are 7260 x 7290.   :alan2cents:

Thanks guys. So regardless, the 7290 is what I should order.

Welp, I'm pretty much ready to order a chunk! I've decided on a 3.73. If I get tired of it, then I'll just add 3.55 to the center section.

If I'm going to be replacing the chunk, there's a few other things I should do while I'm at it.

1) Repack bearings. I suppose any grease will do?

2) Should I replace the axle seals?

3) Do I need to order a gasket for the center section? What RTV to use?

I think that's about it.

I use wheel brg grease in the brgs , I like Castrol but any good quality grease is fine
I would change the inner seals But you need a correct driver otherwise you can destroy the seals trying to install them , if you do not have an installer & it is not leaking it may be better to leave them alone
I have installed both ways , with or without a gasket , I use ultra grey silicone with high oil resistance
Make sure you set the end play correctly too , I seat the axles with a large hammer driving the brgs away from the adjuster side & tighten the adjuster , you want about .010 end play .

And of course you know to be very careful pulling the axle splines past those seals so you don't knick them.

Thanks guys. It should arrive by Wednesday.

When I pull the axles, do I want to simply just add more grease to the bearings? It’s my understanding that they are pretty shielded.

What’s more stock? Using a gasket or not? Even with a gasket, some RTV on both sides a good idea?

I won’t touch the seals.

I’ll measure my yoke when I pull my third member. Assuming I can muscle it out without another hand...

The OD of my tires is 26.1. Obviously when it’s mounted it’s less. Assuming I’ll need a “blue” 38 speedo gear?

Hi all,

Everything is going well. Got everything cleaned. Ready to put new pumpkin in soon.

I've decided to not replace the seals. It's an easy replacement later if they start to leak. same with axle retainer gakets, decided to let those be as well.

I inspected the u-joints. I see some scoring. I believe that they should be replaced.

I measured my U-joint/yoke, and yes, I have the 7290 style.

My question is are both U-joints the same (front and rear of shaft)?

I believe that this is a direct replacement for my rear u-joint:
https://www.oreillyauto.com/detail/b/masterpro-u-joint-4353/cv-driveshaft-axle-16804/combination-u-joint-12825/0c05bd50d9eb/masterpro-combination-universal-joint/355/4507190/1970/dodge/challenger?q=U+joints&pos=0

Is the front one the same?

That does not appear to be a direct replacement u joints as dimensions of both trunions are not the same. More like a conversion u joint. 7290 will use inside clips on all four cups. You can go to Denny driveshaft website to check the info.

I would just pick up two non-geasible Spicer 7290 u joints. A lot of online stores and Napa auto carry them. If your driveshaft is stock with 7290 u joints, front and back are the same.your driveshaft should already be off the car so easy to check.

Cool. I bet these are what I need:

https://www.dennysdriveshaft.com/p463_dana_spicer_5_811x_universal_joint_non_greaseable_7290_serie.html

 :ohyeah: :iagree:

Lots of Youtube videos on replacing u joints, make sure everything are seated correctly, no binding and move freely.

Cool. I automatically thought that I should let my friend replace them since they are pressed in. He has a machine shop and would probably spend way less effort than me!

He could also polish up the end of the driveshaft to remove any markings (the part that goes into the transmission).

Figured I'd just need to owe him some beer.

Dropped off the axles and the driveshaft at a local reputable shop.

Driveshaft: install new u-joints, balance, paint.

Axles: install new tapered OEM-style bearings.

Since I've gone this far, I might as well install:

(1) Tail-shaft seal (which I hear is just a dust seal). Worth replacing this? Does anyone know the part # for NAPA for this? Should I get the one that has a dust boot or without? Here's options:
https://www.napaonline.com/en/p/ATP14581
https://www.napaonline.com/en/p/ATP11424
https://www.napaonline.com/en/p/ATP12049

(2) Axle seals. I'm having a heck of a time finding this. Is this what they call a "wheel" seal, which has both and inner and outer? Anyone have a NAPA Part # for this? "Axle seal" brings up nothing in the search.
Here's an "inner" wheel seal: https://www.napaonline.com/en/p/NOS15460
Looks like that's what I'm replacing. My NAPA wants $20 for it, so I'll probably shop around. Grey RTV before driving it in?

(3) Axle retainer gaskets. I found this at NAPA online (fel-pro) brand. Do I install these dry or use some grey RTV?

#1, That's a toss up? #2, Pretty sure it's the "Inner" ( Easily damaged putting them in)Thin layer of silicone, #3, :alan2cents: I sprayed both sides of mine with "Copper Coat"

Use this  https://www.napaonline.com/en/p/ATP14581  tail shaft seal

And yes shop around but thats the right axle seal...

Thanks randy. I got under there and Checked. It’s the long shroud type.

My seal looks good and it doesn’t leak. Is this more of a dust seal?

They are likely going to polish the yoke. The yoke wasn’t all that bad at all. There was another 1970 challenger yoke there today that was completely rusted. This really is a good car.

Worth replacing (ordering since Napa doesn’t have it) or just run with what I have and stop fixing shit that isn’t broke?

Let me know what to replace. Nothing leaks now back here. But yes, I made some changes.

Also, did Dodge use Monroe shocks? They still work fine.

If the lip area is still pliable I'd leave all three of those seals alone.....  It's easy to do more harm than good....

And the trans seal is definitely a seal.... With an outer dust boot..... 

You offered three seals as the trans seal, any one would work... One was a basic single lip seal with no dust boot... The second one was a single lip seal with a dust boot & the one I said to use is a double lip seal with a dust boot....

I prefer the original look of the output seal with dust boot, you'll probably notice it has a drain hole in it that is supposed to point down.

Thanks guys. I'll likely leave all these seals alone.

Shipping my dizzy off for a recurve. Staying original, and staying with points.

I'd imagine with 3.73s and a more advanced/curved ignotinon id expect to now be in the 14s easily..

Got my axles and drive shaft back. $477..ugh! Well, at least I'll probably never have to deal with them again.

So yet again I'm tempted to replace my axle seals because they gave me a set.

What is so scary about replacing them? I'm assuming you use a seal puller, clean up the area, use some grey RTV, and use a seal driver to drive it in, and whol-a. Is there something about it that does harm vs just leaving in what I have? Just wondering...

Other than that, I'm ready to start bolting everything back up this weekend.

To remove I use a large wrench 1" or larger, hook the seal with the longer side of the open end & use the housing as a fulcrum to lever the seal out....  New seal, fill the back side of the seal with grease, that prevents the garter spring from popping out when you drive the seal....   Clean the axle tube throughly, use a driver that is within 1/16th of the outer diameter of the seal... If your driver is to small the seal will collapse inward.... Driver the seal in till it hits the step, if you don't drive the seal in fully it will rub on the bearing retainer ring either damaging the seal or preventing the axle from sliding all the way into the axle....

It's not hard but there are things to look out for & I've seen more done wrong than you would believe.....

Thanks Randy. It seems like it's an EASY thing to replace in the future if there is a leak, especially since i'm not replacing my brakes yet. No harm no foul.

I'm thinking to keep the new ones in storage. Use what I have. Replace when needed.

The mopar guy made fun of me at the shop for reusing the tapered bearings.

I told him "stock, baby".

He said "have fun adjusting them!"

In all fairness, he said it's not hard, but the green bearings are better hands down. We agreed it's too late for that, since my third member is already installed.

:)

Nope: The greens are junk. The 48 year old tapered bearings are far superior to the ball bearings. The tapered are designed to accept side loads all day long and look how much bearing area there is supporting the load compared to the little ball bearings. Clean them, grease them and then spend about 1 minute adjusting them. Totally superior.
Just another case of Superior Chrysler engineering.

I agree with Sheldon... FWIW I worked for a major bearing supplier for a few years, anything industrial that sees significant loads will have tapered roller bearings....  Green bearings might be easier for people that can't figure out the process of setting endplay/preload but they are not equal to and certainly not better hands down...

Hey guys I just saw this thread. Cool thread for sure. I have been building small blocks and racing them for 30 years and I do have to disagree about the compression ratio comment. The factory numbers were pretty much dead on, its the non hip mass produced rebuilder kits out there that give the dismal compression numbers. For example, my weapon of choice is the 360. They all came with 8.8-1 compression. Every last untouched one I have torn down has had that exact compression. One of the reasons that most motors don't have the compression you think it has ( which I do agree on that part)is the head gaskets. Most rebuilder gaskets are .040 inch thick versus the .015 inch thick factory ones. This .025 increase in thickness is good for half a point alone, then you throw in sunken valves from quick valve jobs and other tolerance stacking and they can be down a full point.

Recently had the pleasure of making some passes in my Challenger T/A. We weighed it on my own race scales and it weighed 3440. It obviously has the six pack aluminum intake and fiberglass hood which your car may not have which will make your car weigh more. My car with BFG 255s on it and a 4 speed had zero traction yet amazingly went 15.90s at 90 mph. Now for the curve ball, it has a stock 318 in it. Years ago I had a stock 340/auto swinger with 3.91s in it and it ran high 13's at 100 mph. None of this really pertains to what your doing but it kinda gives you an idea.


Here is another trick that not many people know about. Take out your stock 727 and replace it with a 999 (otherwise known as a 904) with a low gear set and a 11" converter. I did a back to back comparison on my 12 second Dart with a 360 and it picked up .4 and 5 mph. Not only will your car weigh less but the first two gears will be 2.77, 1.77 and then 1 to 1 for third. Versus 2.45 1.45 with the 727. This little trick really wakes them up and no one will be the wiser. I even did this trick on a stock 68 Roadrunner I had that wouldn't break into the 13s and it picked up .5 seconds and just over 4 mph, I changed the stall too which is why I think it went quicker than .4 I had seen in my small block cars. And yes you can put a small block trans behind a big block.I used a JW ultra bell conversion bell housing.

(https://forum.e-bodies.org/proxy.php?request=http%3A%2F%2Fi573.photobucket.com%2Falbums%2Fss173%2Fmoparchris360%2FIMG_6495_zps7d7tznzv.jpg&hash=e68e4b8c6e47b34dd7a27368c629ba6b15c656c7) (http://s573.photobucket.com/user/moparchris360/media/IMG_6495_zps7d7tznzv.jpg.html)

Quote from: kawahonda on January 06, 2019, 11:09:53 AM
That's a really fast 340!

Yes and an A66.  But can't believe that's stock, there must be some magic under the hood.

Question for you guys:

What's the easiest/safest way to jack up the car in order to replace the speedometer gear? It seems to be located about right smack in the middle.

Two options:

1) Lift up the front end (both sides) and hit it that way.

2) Lift up only the driver side of the car (front left and rear left) and hit it that way.

What option gives the most access?

2)   :alan2cents:

Done!

Quick question for you guys. I'm pretty sure I'll be fine and dandy, but wanted to check.

Speedo-gear successfully installed. 40 MPH is 40 MPH again! :)

I lost 1.5 quarts in the process. My tranny mechanic filled it up with Dex III following shift kit.

I replaced with 1 quart of Dex III.

I had to improvise, so I put in .5 quart of Mopar ATF+4.

I think that's OK, but I wanted to double check.

I think I've asked this before, but I wanted to check. One of my future performance plans is to place on a big block Carter AVS carburater. Is this a simple bolt-up, no mods necessary? What carb part # should I be looking for?

According to hotrod.com, they simply threw on an 800CFM AFB carb on a stock 340 motor and netted 35.6hp and 22.8lbs of torque on factory-spec'd stuff. That's a stupid amount of increase from a carb swap and makes me think it's a great idea to try it. Now of coarse, this doesn't include any drivability tests....just dyno pulls.

"Those old enough will remember that it was popular to swap out the original small AVS (about 600 cfm) for the larger bore version (about 750 cfm) from the 440 Magnum."

Is this true? @RUNCHARGER (https://forum.e-bodies.org/mlist/runcharger_192), @Chryco (https://forum.e-bodies.org/mlist/chryco_49), @1 Wild R/T (https://forum.e-bodies.org/mlist/1-wild-rt_320)?

Quote from: gzig5 on June 05, 2019, 07:51:05 PM
I just put the Edelbrock 9622 between my new AVS2 and RPM Air Gap.  It's only 5/16" thick and acts as it's own gasket.  Too soon to tell but I like it so far.
For a dual plane intake on the street in a stockish motor, I want the divided type.  If you were trying to add more top end and had the cam to support it, the open type may help.

https://www.summitracing.com/parts/edl-9266

:alan2cents:

I just picked this up.

It looks god awe-fully like the exact same one I have right now, except mine isn’t divided. Same material visually.

It does not solve fuel percolation. It helps immensely still, but if you leave the car parked for 30 minutes, gone is your fuel in the bowls.

Then the awkward starting process begins.

Quote from: kawahonda on July 13, 2019, 08:59:41 PM

Quote from: gzig5 on June 05, 2019, 07:51:05 PM
I just put the Edelbrock 9622 between my new AVS2 and RPM Air Gap.  It's only 5/16" thick and acts as it's own gasket.  Too soon to tell but I like it so far.
For a dual plane intake on the street in a stockish motor, I want the divided type.  If you were trying to add more top end and had the cam to support it, the open type may help.

https://www.summitracing.com/parts/edl-9266

:alan2cents:

I just picked this up.

It looks god awe-fully like the exact same one I have right now, except mine isn't divided. Same material visually.

It does not solve fuel percolation. It helps immensely still, but if you leave the car parked for 30 minutes, gone is your fuel in the bowls.

Then the awkward starting process begins.

This is one of the reasons I went with a electric fuel pump and a return line mounted to the regulator thats mounted in the engine bay. Eliminates issues....

Quote from: kawahonda on July 13, 2019, 08:59:41 PM

Quote from: gzig5 on June 05, 2019, 07:51:05 PM
I just put the Edelbrock 9622 between my new AVS2 and RPM Air Gap.  It's only 5/16" thick and acts as it's own gasket.  Too soon to tell but I like it so far.
For a dual plane intake on the street in a stockish motor, I want the divided type.  If you were trying to add more top end and had the cam to support it, the open type may help.

https://www.summitracing.com/parts/edl-9266

:alan2cents:

I just picked this up.

It looks god awe-fully like the exact same one I have right now, except mine isn't divided. Same material visually.

It does not solve fuel percolation. It helps immensely still, but if you leave the car parked for 30 minutes, gone is your fuel in the bowls.

Then the awkward starting process begins.

Almost sounds like the bowls are siphoning off or something else is wrong in the carb or electrical system.  I can't see several ounces of fuel evaporating/boiling off in that short of time.  Maybe more initial timing would help?  Mine starts on the first rev when hot or first thing in the morning.  Wasn't so with the old Holley that was replaced.

Carb is pretty darn clean...it's been rebuilt.

I haven't verified that the bowls are empty after an hour or so of sitting, but it sure sounds like it when it needs to be turned over 3-4 times. Acting like no fuel is in the bowl.

Initial is dialed in at 15. I may consider more initial with colder plugs, but with the current Champion 12 plugs that I have now, 15 is the limit.

The only thing I can think of is this *may* have something to do that my cross-overs are not blocked. I don't really think that has anything to do with it, because blocked off cross-overs the engine will still come up to engine temp, just takes longer.

Blocking the crossover has always been worthwhile in my experience , exhaust heat is higher than coolant temp

Just for comparison sake ---

My Barracuda with a frankenstein non original powertrain ran 15.4 two times in a row at Nats last year.

I wasnt all that pleased until I started reading that that is what the 340s used to do stock in the ebodies.

My engine is a 318 with J heads, a purple cam (unknown specs), Dougs headers, edelbrock performer intake and 4 BBL carb (1405  600cfm), 727 automatic with a 2400 stall in it, 3.55 tru-track rear end.

The car doesnt do great burnouts or pull all that hard off the line but once it hits 3k and above she pulls hard.....

Ive toyed with the idea of 3.90s and a overdrive ...then I start thinking 408 stroker...LOL

Oh if money was no object.