Check Out That Chassis

By Jim Salemi


Question 1 Answer

Hi, I have a ’66 Nova with a four line and have been having some problems with the car going to the right off the line. I have added preload to the right rear by shortening the top bar, but it still has not taken care of the problem all the time. I decided to go through everything today and found a couple of things. The pinion angle was about six degrees up, so I corrected that and set it to 1.5 degrees down. I find that when I install the top right bar so the bolt slips in, the passenger side sits lower than the driver, so I believe I should tighten the passenger bar until the car is level and that would be zero preload. The car also sat lower in the rear, so I leveled the car before I set the pinion angle. Could any of these things been causing my problems? If this does not work, what should I try?

The car runs 6.5s in the 1/8 at 102-103 with a 1.42 60 ft. It has a 10 point chromoly cage and you can see that it is not twisting when leaving the line.

Any help would be greatly appreciated.


Kirk Wilde

Kirk, First off I would like to explain a couple of things to you. The only
Real way to adjust pre load in a four link car is to do it on scales. That is the only way you can be sure of what the effect of the four link adjustment is really doing.

Secondly, just because the car is level that doesn't necessarily mean that it does not have any pre load in the chassis. Things could be fabricated improperly, not installed straight, or like the question asks not adjusted properly, all being a factor of preload. One other thing is that the rear end may not be properly squared in the car, causing the car to not go straight. I would also like to explain the concept of pinion angle and proper way to measure. In your question you state that you leveled out the car before measuring pinion angle. The leveling actually doesn't matter because the relationship of the driveshaft to the pinion stays the same. Consider the driveshaft to be 0 degrees and the difference of the driveshaft to the pinion is the (pinion angle) measurement. With your car you’re looking for that measurement to be .5 degrees down.

With regard to the car driving to the right, one thing that racers always
overlook is tire roll out. Measure the tire size in circumference. The proper way to measure circumference is to measure the tire at the middle of the tire. Obviously you would want them both to be the same. The last situation that I would like to discuss is that of something just being worn out in the rear suspension or some place in the car. You should check out all the rod ends in the suspension, make sure nothing is cracked, and check all the bolt holes for a tight fight on the bolt itself.


Jim Salemi



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Check Out That Chassis — 3/8/03


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