Shooting the breeze. What’s the 1/4 mile time of a 340 challenger?

[kawahonda]

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?

[Cuda Cody]

I would guess low 15's.

[Cuda Cody]

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

[RUNCHARGER]

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

[340challconvert]

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.

[RUNCHARGER]

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

[1 Wild R/T]

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

[ledphoot]

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..

[kawahonda]

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.

[RUNCHARGER]

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.

[JonH]

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...

[kawahonda]

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

Do our an a66s really weigh 3750?

[73chalngr]

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

[Shane Kelley]

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.

[IRON MAN]

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