Could some one tell me what the stock front-to-rear weight bias is for a 1966 Barracuda (or Valiant)? All I could find on line is total weight; I'd like to know how much weight is on the front wheels and how much is on the rear wheels. Thanks....

I am Just taking a guess here but I would say 60 or more% front on a stock type vehicle / A body.


My drag car is close to 52/48 now... Plans to move engine rearward a bit to solve this,

Greg

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Stock is something like 55/45. I will try to look up my numbers on this. Cuda will likely be more on the rear due to the big rear window and additional structure, I think. They were pretty well balanced from the factory.

Lou

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Thanks for the input guys. Lou, if you've got some stats on this I'd be interested in seeing what they say. Greg, my 'cuda is set up for running Bonneville, so I want to make sure I have enough forward weight vs. in the rear. My goal being that I have my center of gravity in front of the center of pressure. At Speed Week, I was experiencing some drift or lift at about 120 mph. Two contributing factors could be that with only 49% on the front wheels, my center of gravity might have moved rearward of the center of pressure. Like an arrow trying to fly backwards; not good. Other factor could be my scrub radius. To get my skinny 4.5" non-Mopar wheels to fit the disc brakes, I was running 1/2" spacers. I've since downsized my calipers with my grinder, so that's been corrected.

Assuming Mopar built their cars with the center of pressure behind the center of gravity (did they?), I'm looking to see exactly where the designed center of gravity is.

Speaking of high speed drift, what are you doing about airflow?
I always heard that the fastback made a nice airfoil shape that would result in lots of rear lift.
Tom McEwen's crash, Petty's PopSci Formula S test, etc.; airflow is usually blamed for moving the car around a lot.
Anyone have a wind tunnel handy?

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Yeah, the cuda fastback is good for airflow (drag reduction), but also makes lift.

Bob, it took me a minute to realize it was Mr. Bonneville! Glad you are pushing forward.

I rechecked my weight numbers and I couldn't find my stock 63 Dart weights, which I know I have somewhere. Anyway, my 68 Dart (close to stock wt bias) is 55/45 with the engine moved a bit forward and the turbo stuff on there, and an 8.75" rear axle. I have earlier weights that were 54/46 range (w/driver), no turbo but battery up front. 64 Dart is 53/47, but was originally more like 55/45 since I have moved weight rearward and lightened things. Wild guess is that yours is 55/45 or close.

I am pretty sure that Chrysler never did wind tunnel testing and probably did not worry about center of grav vs. center of pressure. These cars were just not supposed to go that fast.

I just read some things (Ehrenberg and others) that too much positive caster is not the best for this suspension geometry. You get "spooky" handling with >+3-4 deg positive. In retrospect, I have to agree with this, by road course testing and top end seat-of-pants feel. My Project V with +6 does not feel as nice at 110+MPH as my Darts have with +2 or up to +4. I may pull back my numbers to +3 from now on. My 68 Dart has +2 and it feels rock solid at 130, 64 Dart has had +3-4 for a long time - nice feel. Lesson: if more is good, even more may not be better.

Cheers,

Lou

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Guys, thanks for the additional input; very helpful. 6inhead I looked up the Petty article, which I hadn't seen before. His comments about how the air move around the 'cuda better than the 'stang was encouraging. And his remark about handling at 120 was also interesting.

BTW I spoke with Wilford Day a little while back, and he told me he had no handling issues back in the day when he ran his '64 'cuda at over 140 mph on the Salt. Said he had no ballast, and he ran street tires. Yet I was drifting slightly at about 120 mph (before my motor cooked). But then my tires are skinny 4.5" front runners with 60 psi.

With the 170 sl6, I run in F/CPRO (Classic Production), and in Production class I'm not allowed to do any streamlining. I have to keep all the doorhandles, headlights, taillights, bumpers, fuel tank, etc. To keep the wheels on the ground I have to work with ballast, and at Speed Week I ran with 400 lbs. of lead placed on the floor and forward of the rear axle. Adding that weight in that location put my bias at 49% front & 51% rear, so I'm guessing I might have gotten my center of gravity too near or maybe even behind the center of pressure.

So the fix I've been working on is to add more ballast at the front end. I've just finished a steel plate tray that mounts between the radiator support and the K-member that I hope to load up with 125 lbs. of lead. Add another 50 lbs. inside the front fender wells, and I'll be back at 52% at the front. Another piece here or there, or pull some lead from the rear, and I'll be near the 54% ballpark that Lou suggests above.

Lou, thanks for those bias numbers. Seems like 53% - 55% should do it for my next round - at least it will beat the 49% that I had!

Interesting comments on the alignment. Other Salt racers have advised me that I should go for as much positive caster as possible and as close to zero camber as possible, but this Mopar specific info might override that. I might consider dropping some of my 5+ caster and getting my -.7 camber closer to zero. But I think that scrub radius factor has to have helped me, too.