E-Bodies.org Cuda Challenger Forum

My Barracuda is really sucking down the gas - approx. 6 mpg in it's current setup.  It has a 416 stroker, Edelbrock Performer RPM dual plane intake, ported J heads, TTI headers into a 3" exhaust system, comp Xtreme CH292 cam and a Edelbrock Thunder AVS 800 cfm carb.  4 speed and 3.55 gears.  14" rims with 245 60 tires.  I've leaned it out by changing the metering jets, primary rods and spring and it still runs very rich and sucks down the gas.  I didn't expect a good mpg with this setup, but I expected a little better than that.  Is the 800 cfm carb too big? Would a 650 cfm carb be better?

800 sounds like a lot to me.  @Chryco Psycho (https://forum.e-bodies.org/mlist/chryco-psycho_4)    :notsure:

That doesn't make sense.  At 9 to 1 compression it shouldn't ping at all.  That's a very safe compression.  I would think it would run best around 36.  I run 37 to 38 sometimes too on my small blocks.

Quote from: erik70rt on June 05, 2017, 09:05:43 AM
Initial is set at 15 and total is about 32.  Any more and it knocks/pings under acceleration. Using 93 octane gas.  Ratio is 9:1.

I can check/set the timing again, but where it is seems to be the sweet spot.

I'm using 16 initial with 11:1 on 93. It really runs awesome at 21-22 on 110.  Do you have a wide band A/F gauge? One of the best investments I made for tuning was one of those.

I was having a similar issue and it was my timing the whole time. Everything from improper initial advance to my total and how fast the curve was. I could not make lean or rich conditions with my carb until that got set correctly. 

I'm not saying that your problem is all timing but your mileage should be better than that unless like Chryco said about the heavy foot thing. :)       

Lack of quench will cause detonation well below safe range

Lack of vacuum will cause a lot of problems.  Good cams that make good vacuum can not be stressed enough.  That's why I run the Mr. Six Pack cams.  They make great vacuum and that in turns makes it easy to tune and great running engines.  The 340 engine we just tuned on the dyno last Friday made 18 pounds of vacuum at 850 idle.

What is your vacuum at idle?

Quote from: Cuda Cody on June 05, 2017, 10:05:28 AM
Lack of vacuum will cause a lot of problems.  Good cams that make good vacuum can not be stressed enough.  That's why I run the Mr. Six Pack cams.  They make great vacuum and that in turns makes it easy to tune and great running engines.  The 340 engine we just tuned on the dyno last Friday made 18 pounds of vacuum at 850 idle.

What is your vacuum at idle?

I'll have to recheck that since I don't remember off the top of my head.

Quote from: Chryco Psycho on June 05, 2017, 09:56:30 AM
Lack of quench will cause detonation well below safe range

It would also backfire through the exhaust when you let off the gas at highway speeds. 

I have not romped on it much since it's only got about 700 miles in it since the build. 

I would agree with Neil on the Proform carb but if you want to improve gas mileage you could move towards a vacuum secondary setup. But as he said before you only improve your gas mileage as long as you can restrain from overuse of the fun pedal.

:burnout:

In my opinion a manual trans car works better with a mechanical secondary carb. With a vacuum secondary it will close the secondaries between shifts. Then pull them back open. Automatic trans I like the vacuum secondary carb. I run 11-1 compression with 38 degrees total timing with no spark knock on 93. I run one of my 340's with the timing locked at 38 degrees. Instant throttle response.  I do have aluminum heads which does help with detonation. I have had some 340's that really run great with 650 cfm. The smaller the carb the snappier the throttle response. My preferred carb is a 750 mechanical secondary with a 4 speed. My favorite carb of choice is a Quick Fuel Q750. Sweet right out of the box.  :alan2cents:

Funny I don't have any problems with a vacuum secondary carb and a manual car. I have one on my Cuda right now.

The secondaries don't close that fast between shifts. If you take off the vacuum secondary unit and pull the diaphragm closed you will see it closes pretty slowly.

I have had plenty of double pumpers in my past and they definitely have their place but it wouldn't be on a car where you wanted better gas mileage IMHO.

My list of things to do tonight:

1.  Install the lightest set of springs I have in the carb.
2.  Check on/reset the advance on the distributer
3.  Set timing with more advance
4.  Recheck vacuum
5.  Get cam specs posted
6.  Have cold one  :drinkingbud:

I changed out the springs in the carb to the lightest set I have - 3 in hg.  I reset the timing to approx. 18 degrees initial and 36 at 2500 rpm.  The vacuum at idle is 5 in lbs and 18 at 2500 rpm and steady. 

My cam is Comp grind 292H-10 part # 20-243-4 - part of the Magnum series (not Xtreme like I posted earlier).  It has .501 lift intake and exhaust.  Duration @.050 is 244 intake and exhaust.  Lobe lift .3340 for both and lobe separation is 110.0

I also rechecked my engine specs and it's 10:1, not 9:1.  So I may need a higher octane gas, too.

Maybe I'm to cautious, but I don't like being under 10 to 12 on vacuum at idle.  And if you have 10.1 to 1 with iron heads you might have to run some race fuel to get it to not ping.  I try not to go over 9.5 to 1 with iron heads.

With that little vacuum does it idle okay?  Do you run power brakes on that low of vacuum?  :huh:

Plus you have 3.55's which is a great rear, but not as friendly on fuel as maybe something like 3.23's.  If it's running good and you like everything else, you might have to be okay using fuel.  But 6 MPG sounds really low for what you have.  I personally think 800 is a lot of carb.  Do you have a buddy or someone you can borrow a 750 and see how you like it?

Quote from: erik70rt on June 05, 2017, 04:25:04 PM
The vacuum at idle is 5 in lbs

It runs well at idle.  I have it set around 850 rpm. 

I knew I wouldn't have enough vacuum for power brakes, so I installed manual discs in front and drums in back. 

I'll see if I can scrounge a 750 from someone.  If the Eddy carbs are that fickle about vacuum (I was not aware they were), then I might switch to the Proform carb that others recommend.

The carb might be fine with that little vacuum.  If it runs and idles great, the only change it to see if you can get some better fuel mileage.   :alan2cents:

Quote from: erik70rt on June 05, 2017, 06:00:34 PM
It runs well at idle.  I have it set around 850 rpm. 

I knew I wouldn't have enough vacuum for power brakes, so I installed manual discs in front and drums in back. 

I'll see if I can scrounge a 750 from someone.  If the Eddy carbs are that fickle about vacuum (I was not aware they were), then I might switch to the Proform carb that others recommend.

Quote from: erik70rt on June 05, 2017, 04:25:04 PM
I changed out the springs in the carb to the lightest set I have - 3 in hg.  I reset the timing to approx. 18 degrees initial and 36 at 2500 rpm.  The vacuum at idle is 5 in lbs and 18 at 2500 rpm and steady. 

My cam is Comp grind 292H-10 part # 20-243-4 - part of the Magnum series (not Xtreme like I posted earlier).  It has .501 lift intake and exhaust.  Duration @.050 is 244 intake and exhaust.  Lobe lift .3340 for both and lobe separation is 110.0

I also rechecked my engine specs and it's 10:1, not 9:1.  So I may need a higher octane gas, too.

OK now we are getting to the real info !
5" at idle makes sense , cam has a lot of duration with very little lift , far better grinds are available if you are into a cam swap .
There is no reason why you cannot get around 10+ MPG but a better carb will make a lot of difference , you want a carb with adjustable air bleeds with low vacuum like that .
You may have to back the timing down again as your heads have no quench , or add better fuel .
what are you running for T stat temp ?

Thermostat is 160.

I can't get race gas around here.  Best I can do is the 93 octane.  I'll have to find that post about octane boosters and read up on which ones are good.

Change to 180*

Why?  :huh:  Wasn't the goal originally to get the car up to operating temp as fast as possible, so they used a stat to stop the coolant until it was hot?  So in a daily driver it makes sense to use a 180 and let the car warm up.  If the car is like most E-Bodies these days, it's not a daily driver and usually only driven on nice warm days.  So getting the car up to temp fast isn't as big of a deal as it was back in the day.  I want my engine to stay as cool as possible as I manly go cruising and sometimes sit stuck in traffic.  I have even removed the stat all together and instead use the wide 3 core (or 4 core) radiators with a custom dimple core to slow the water down where it's needed.... in the radiator.  I don't want the bottle neck of the coolant flow to be in the stat, I want the coolant to get to the radiator, then the dimples slow it down and get the coolant as cold as possible before it goes back to the engine.  I never had over heating trouble even when I'm sitting in a parade idling in 100 temps.   :alan2cents:

Quote from: Chryco Psycho on June 05, 2017, 07:20:29 PM
Change to 180*

The engine can run too cool accelerating wear inside the engine & cause incomplete combustion ,ie back fire out of the pipes

Cody

Remember you have to slow the flow to get the coolant to cool while its in the radiator. Otherwise you are just passing warm coolant through the system. If you reduce the amount of time the coolant can exchange heat with the radiator it's kinda self defeating.

B

Quote from: Chryco Psycho on June 05, 2017, 09:41:25 PM
The engine can run too cool accelerating wear inside the engine & cause incomplete combustion ,ie back fire out of the pipes

That's an easy enough change.  I'm not going to change the cam at this point.  How about plugs?  I'll have to check what I have for the temp.

A cooler plug can help with detonation but it may foul up quickly too

Quote from: Chryco Psycho on June 05, 2017, 08:18:23 AM
  :iagree:
I cannot even find specs for a Ch 292 but I am guessing it has 292* duration which is huge I doubt you have 5"of vacuum at idle !
Who picked that cam?

I forgot to answer this question.  The guy who does my engine machine work picked it.  I wanted something with more lift, but wanted to stay with hydraulic lifters for a street engine.  He recommended this cam for it's streetability saying he used them before with great results.

Quote from: Cuda Cody on June 05, 2017, 08:49:54 PM
Why?  :huh:  Wasn't the goal originally to get the car up to operating temp as fast as possible, so they used a stat to stop the coolant until it was hot?  So in a daily driver it makes sense to use a 180 and let the car warm up.  If the car is like most E-Bodies these days, it's not a daily driver and usually only driven on nice warm days.  So getting the car up to temp fast isn't as big of a deal as it was back in the day.  I want my engine to stay as cool as possible as I manly go cruising and sometimes sit stuck in traffic.  I have even removed the stat all together and instead use the wide 3 core (or 4 core) radiators with a custom dimple core to slow the water down where it's needed.... in the radiator.  I don't want the bottle neck of the coolant flow to be in the stat, I want the coolant to get to the radiator, then the dimples slow it down and get the coolant as cold as possible before it goes back to the engine.  I never had over heating trouble even when I'm sitting in a parade idling in 100 temps.   :alan2cents:

Quote from: Chryco Psycho on June 05, 2017, 07:20:29 PM
Change to 180*

:iagree:
But this will always be a debate. I like a 160 in my cars also. I don't need it to get to 180 and heat soak everything so the cooling system has to play catch up. I would rather start cooling at a lower temp. I also have removed T stat all together on some hot running cars. I does keep them running cooler. 

My Dad told me decades ago that an engine has to be at operating temperature to run efficiently and I have always agreed with that. I like to run a 180 or 195 in my cars and make sure the cooling system is up to par so it will control it there. The newly formulated gasoline sure doesn't like heat though. Hence injection but that's another topic.

Quote from: erik70rt on June 05, 2017, 04:25:04 PM
I changed out the springs in the carb to the lightest set I have - 3 in hg.  I reset the timing to approx. 18 degrees initial and 36 at 2500 rpm.  The vacuum at idle is 5 in lbs and 18 at 2500 rpm and steady. 

My cam is Comp grind 292H-10 part # 20-243-4 - part of the Magnum series (not Xtreme like I posted earlier).  It has .501 lift intake and exhaust.  Duration @.050 is 244 intake and exhaust.  Lobe lift .3340 for both and lobe separation is 110.0

I also rechecked my engine specs and it's 10:1, not 9:1.  So I may need a higher octane gas, too.

with 244 * @ .050 you could be almost .600 lift with a flat tappet solid , with only .500 lift you could be in the 220* range   , 292* advertised is huge & thus the 5" idle vacuum
This is what I would have suggested https://www.summitracing.com/int/parts/lun-10200703/overview/make/dodge

I had a 268 in a 340 I built a few years ago.  Loved that cam. 

What do you all think of this carb?  Anyone ever use it?

https://www.summitracing.com/parts/qft-br-67257

Looks like a basic Holley design.  Should be easy to tune if the quality is there.

Get the Proform  similar carb better quality & price , the ones I listed have a billet base plate not cast like that one has .
Nothing wrong with QF just you pay more for the same thing .
I would also lean toward using the Street Double pump not the vacuum secondary  better milage when you foot is out of it & far better response when your foot is into it

Ordered the Proform 67213 you recommended. 

Carb is arriving today.  As I have never worked with a Proform, any tips for getting it tuned well?  Air Bleed size/setup?  Fuel line (single or dual feed)?  Linkage adjustments?

I believe there is a Holley tuning guide I wrote in the reference material section , go through the basic tuning& get it as good as you can then we can get into air bleeds etc . low vacuum requires smaller air bleeds you ca see the effect by inserting a small diameter wire into the bleed while running , [do not drop it in !!] but the engine will change as you insert the wire

Quote from: erik70rt on June 14, 2017, 06:36:02 AM
Carb is arriving today.  As I have never worked with a Proform, any tips for getting it tuned well?  Air Bleed size/setup?  Fuel line (single or dual feed)?  Linkage adjustments?

Put it on right on and see what happens. You may not need to do anything other than idle adjustment. These newer high end carbs are pretty sweet right out of the box. I run the Quick Fuel carbs and they use the Pro Form main bodies. The idle air bleeds are the only things that I usually have to mess with. But I always run larger ones. I think they come with 70's and I usually end up around 85's on my motors. If your eyeballs are bleeding from the fumes at idle you will need larger ones to lean out the idle circuit. But like I said. See what happens.

Both Shane and Chryco know what they are talking about.  Get it going and then let us know how it drives.  We can help you once we know what is happening.  I can also walk you through a few things on the phone if needed.  But get it on and see how it works first.

Quote from: erik70rt on June 14, 2017, 06:36:02 AM
Carb is arriving today.  As I have never worked with a Proform, any tips for getting it tuned well?  Air Bleed size/setup?  Fuel line (single or dual feed)?  Linkage adjustments?

Thanks, Cody.  I'll let you all know how it goes.

Make sure you equalize al 4 idle screws &make 1/16 turn adjustments

I didn't get it installed last night.  Do I need one of the 9 1/4" dual feed fuel lines like the double pumpers use?  I also don't have the Mopar adapter for mounting the throttle cable so I'll order one of them today. 

I your able you can make your own fuel line with 3/8 brake line from the parts store. Then use a 3/8 flare T to connect the front bowl line and the rear. Are you running automatic trans?

4 speed.  3.55 gears in back.

Your stock throttle bracket might work. If it looks like this one in the top pic it will. You won't need the return spring bracket that's in that pic either. You can run the return spring from the bottom of the carb throttle arm back to your cable bracket. Looks cleaner that way. Bottom pic shows the return spring configuration.

Not the bracket - that should work.  I mean the small extension that you need to mount on the carb throttle lever to attach the throttle cable.

I didn't need that with my manual trans car but did on the automatic car for kick down. Top pic manual and bottom auto with the bracket you referred to.

Sweet.  But I need that bolt on stud, too. 

Update!  Found one on an old carb I had sitting around! :veryexcited:

Remove it from the carb you have on the car. If you have the one like on my automatic car you can cut the long unthreaded part of stud off and put it in the throttle bracket from the other side. Use a thinner lock nut to hold it from the inside instead of the long one that holds it now. 

Another question - pcv line.  It was a straight 3/8" input on the Edelbrock.  For the Proform, I see a 3/8 connection in the back of the carb (presume it's for the brake booster connection) and two small 1/4" connecting ports on the front left of the carb Presuming these are the pcv connections).  I already hooked the distributor to the connection on the side of the carb.  How did anyone hook up the pcv line?  Did you run a 3/8" line off the pcv valve to a connector to reduce the lines to 1/4"?  Did you just hook it to the 3/8" connection on the back? 

Quote from: erik70rt on June 16, 2017, 05:44:24 AM
Another question - pcv line.  It was a straight 3/8" input on the Edelbrock.  For the Proform, I see a 3/8 connection in the back of the carb (presume it's for the brake booster connection) and two small 1/4" connecting ports on the front left of the carb Presuming these are the pcv connections).  I already hooked the distributor to the connection on the side of the carb.  How did anyone hook up the pcv line?  Did you run a 3/8" line off the pcv valve to a connector to reduce the lines to 1/4"?  Did you just hook it to the 3/8" connection on the back?

I used the port on the back of the carb for PCV. I have manual brakes so I didn't have to contend with that. But the brakes will need to go on a different port. Usually on the intake manifold itself. Don't try a T fitting for that and the PCV. You will lose vacuum for the brakes if you do that.

I have manual brakes, so that's not an issue.

Got the Proform carb installed today.  Had to do some fuel line re-plumbing, but nothing bad.  All I have to say is............


WOW!!!!  What a difference!   :woohoo: :woohoo: :veryexcited: :veryexcited:


Kudos for the carb recommendation.  :thankyou: It idles MUCH better at 850 rpm.  Response was good off the line and jumped when the 4bbl was kicked.  When you came to a stop it didn't struggle to keep running.  I also didn't have my garage smell like gas when I put it away. 

Now to start the fine tuning. 

Yup What a difference !!!

Quote from: erik70rt on June 17, 2017, 02:36:14 PM
Got the Proform carb installed today.  Had to do some fuel line re-plumbing, but nothing bad.  All I have to say is............


WOW!!!!  What a difference!   :woohoo: :woohoo: :veryexcited: :veryexcited:


Kudos for the carb recommendation.  :thankyou: It idles MUCH better at 850 rpm.  Response was good off the line and jumped when the 4bbl was kicked.  When you came to a stop it didn't struggle to keep running.  I also didn't have my garage smell like gas when I put it away. 

Now to start the fine tuning.

That's excellent!  :banana:

Ha, ha: One day I'm going to buy a new, state of the art carb. I've played with cars for 45 years and generally I buy carbs that other guys couldn't get running right, or old #'s carbs and I go through them and use them. Just once I'd like to take a new one out of the box and bolt it on.

Quote from: RUNCHARGER on June 18, 2017, 09:28:37 AM
Ha, ha: One day I'm going to buy a new, state of the art carb. I've played with cars for 45 years and generally I buy carbs that other guys couldn't get running right, or old #'s carbs and I go through them and use them. Just once I'd like to take a new one out of the box and bolt it on.

You've done it the hard way long enough, you don't need no stinking ez-carb.... :rofl:  Personally I think the fuel these days is a huge part of the problem....

Actually yes: I installed a dual body Fitech on Greg's car last year and that's the way to go. Easier to punch numbers in than turn a screwdriver.

Time to start tuning.  All I did when I took it out of the box and fired up the car was set the idle and idle mixture screws.  I let the car sit for a day and then started it.  It was getting way too much fuel at start up so a choke adjustment is in order.  Once I have that done, what is the best way to analyze/adjust the air bleed settings?

Quote from: RUNCHARGER on June 18, 2017, 09:28:37 AM
Ha, ha: One day I'm going to buy a new, state of the art carb. I've played with cars for 45 years and generally I buy carbs that other guys couldn't get running right, or old #'s carbs and I go through them and use them. Just once I'd like to take a new one out of the box and bolt it on.

You have no idea what you are missing !! Efi is still better though

Quote from: erik70rt on June 19, 2017, 06:14:02 AM
Time to start tuning.  All I did when I took it out of the box and fired up the car was set the idle and idle mixture screws.  I let the car sit for a day and then started it.  It was getting way too much fuel at start up so a choke adjustment is in order.  Once I have that done, what is the best way to analyze/adjust the air bleed settings?

there is a tuning guide in the reference section go through all that first , I would have the choke so it is just barely closed when cold if that , make sue the float level is right , sounds like the power valve is ok , if the idle screws are responsive & around 3/4 -1 1/4 turns out your idle bleeds are fine so now you need to work on jetting youcan go by plug color or a O2 sensor is better to tune with Proform generally sis very close with the bleed size so that would be one of the last things I would tweak
you need to get the accelerator pump p& jetting dialed in first

You mentioned that once before and I printed the tuning tips out.   Then forgot all about it!  LOL