Check Out That Chassis

By Jim Salemi
3/9/04

 

Question

Answer

Jim, We have a '96 Jerry Haas Pro Stock Olds Cutlass with 500ci Olds engine. For many years the car ran straight as an arrow with 1200hp engine, Lenco 4-speed and 8" L&T clutch with 4.86 rear gears. We fitted new engine with 60 more hp, a G-Force 5-speed trans and new East West 8" clutch. The car has the same Koni double adjustable rear shocks and 95 lb. spring with top adjustment 9 off soft and lower at 5 off soft. The front lamb struts 1/4 turn driver side and 1/2 turn passenger side off full hard. 4-link is exactly the same as always, about 47-48". Wheelie bars are 6" driver's side and 5.5" passenger side. Preload is virtually neutral as it always was biased to maybe 1/8 of a flat negative if any at all. Weight bias is 49.1, rear total car weight is 2256 lbs. Corner weights are 626 LF, 523 LR, 527 RR. Ride height rear is 5" and 3 3/4" front. With the new setup the car will not leave the line straight. It hits the passenger side wheelie bar really hard and goes left. Can a bad rear shock or shock spring cause this? Do you have any other suggestions? The only thing that happened between the combo changes is that the car sat on a car hoist (suspension free) for nearly three years and was not raced. Gene Kuklovsky

Gene, Thanks for the question: In your case the first thing I would do is inspect the chassis and make sure there are no broken welds, tubes, or suspension components. I would also make sure that the rod ends in the four link are still tight. If any of these are broken or worn out the load of the will not be distributed properly through the chassis. I would keep the wheelie bar and instant center settings the same. Here are some things to consider. You're making 60 more horsepower which should also produce more torque, and you have went from a 4-speed Lenco, to a 5-speed G-Force tranny (no relation to my chassis shop). Both of these aspects will put more force into chassis, hence needing more preload. Remember that the gear ratios in the G-Force are most likely not the same as the Lenco. I would tend to think that the first gear in the G-Force trans is more than the Lenco. I would start by making a preload adjustment and would make small moves until it goes straight. It should not take more than one flat of negative preload to make it work. (negative preload = makes right top bar longer) Thanks again. Hopefully this will help. Jim Salemi G-Force Race Cars.

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Check Out That Chassis — 2/9/03