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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.
Thanks,
Kirk Wilde
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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.
Thanks,
Jim Salemi
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