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Ideal weight distribution for Ladder bar car ???

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Ideal weight distribution for Ladder bar car ???

Postby cudabin » Fri Oct 13, 2006 12:20 pm

I have a 67 Cuda notchback running 9.94 at 136.2 with a 1.43 60 foot.

I am going to convert 8 point bar into 10 point cage to get legal for 9.XX's

Car weighs 2,995 #'s with driver and full fuel including a 125# ballast bar in trunk. Rear axle weighed 1,335#'s and front 1,660 so weight distribution is currently 55% front / 45% rear.

Car does not pick up the front tires at all, and rear is mostly neutral with some slight separation. Traction is marginal at our home track, so i thought I should slide the motor back before the Cage gets built.

What is the ideal weight distribution front/ rear ?? 50/50 ?

How far back does the motor have to go to make a difference ??

Thanks for any and all input!

Arnie
8.97 @ 149.9 w/ 1.25 60' so far... 67 Cuda
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Postby Ed-vancedEngines » Fri Oct 13, 2006 1:46 pm

I suggest to get rid of the weight bar unless you are trying to make a certain weight class.

I do not understand why the front of that thing is so heavy though. Are you using the BB cross member and torsion bars on it? Is it a cast iron Hemi?

The theoretical ideal front o rear weight ratio now is more car and class specific. What is working great in one car might not be good in another car. 50/50 is too much weight on the rear of any drag car now. Typical 10.5 cars are running with a 52% front - 48% rear to 53% front w/47% rear. But I doi know of one that is at 80% front with a 4 link and is still working great. I see a lot of guys now adding weight to the front to keep it down some.

I aploogise for doubting you but that weight distribution for a Baracuda to me just does not sound right.

We have a former RamChargers Team Engineer here as a member. I am sure he has much experience with your car. If he does not chim in here in this thread. PM him at Billy Shoppe.

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Postby mikeandnatasha » Sat Oct 14, 2006 2:12 am

My times are about the same as yours. Ive run a 9.96 at 134 on a 1.44 60 with ladder bars front pivot set on the highest setting...almost toching the floor pan, coil overs in back with 140 lb springs, slight preload on the right and two clicks of the shocks stiffer right side, 210 lb front springs and 90/10's. 4000 stall converter C4 .

Same deal here. I'll pull the front end maybe 10 inches if I'm spraying 150 horse off the line but the corresponding rise in the back from the hi mounting of the ladder bars front pivot keeps the front rise down. If I switch to a lower front pivot point I'll get a lot more front end rise but I unload the chassis too fast and as soon as the front end comes down I lose traction. Since I can run 10.00 or slower with my 8 point cage I'm content to run consistently in the 10.10 range and call it good. I'm reasonably sure if I were to open up the nitrous jetting to 250 I'd pull clean to 9.6 ish since I have no lack of traction even with off track testing of higher nitrous settings.

Image
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Postby BillyShope » Sat Oct 14, 2006 7:40 am

Yes, that's a little more weight on the front than I'd expect. Both cars should be able to knock off at least another couple tenths from their 60's.

Go to pages 17 and 18 of my blog and you'll see what you have to do as far as weight distribution is concerned:

http://home.earthlink.net/~whshope

With the torsion bar front end, it's relatively easy to make some beneficial changes. Go to a high RATE torsion bar at the right front and a low rate at the left front. Check out the effects with the traction dyno. (See blog.)

The distance that any component needs to be moved to the rear, to accomplish a desired change in rear weight percentage, is determined by the following:

distance = LWD/M

where "L" is the wheelbase, "W" is the total weight, "D" is the difference between the desired fraction of weight on the rear and the present fraction, and "M" is the weight of the item being moved.

(Ed, my name is spelled with one "p." With two, I become a place where they sell overpriced antiques.)
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Postby RW TECH » Sun Oct 15, 2006 3:06 am

Mike,

You're a man after my own heart. Here's what I ran in the mid-80's with an iron 388 CID Cleveland & C4:

Image

Best 60' at local track was 1.352 & best ET/MPH was 10:09 @ 133.76. 3412 lbs. with me onboard & foot braking it.
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Postby cudabin » Tue Oct 17, 2006 1:52 pm

Perhaps the weight distribution is better on the fastback Cudas with that big back window? Mine is a Notchback. The motor is in the stock location but uses a aluminum motor plate.

Would the MP Drag race torsion bars store more energy and transfer better ?? I was always told they were too loose for a 9 second car??

I would like to get the front tires about 6" off the ground and carry them to ensure all the weight transfer I can get as our track has marginal prep...

My 60 foots are consistant at 1.43 - 1.45 but i think they should be better.

Thanks for the info.

Arnie
8.97 @ 149.9 w/ 1.25 60' so far... 67 Cuda
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