1972 GS 455 Tube Chassis Drag Car
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Background
George has really been around the block in this car, and we have know him for a lot of years. He started off with a 10" tire car, then wanted to back halve it, but retain the original rear seat. Unfortunately, the shop that did it, decided that it was unnecessary to kick the rear frame rails up over the axle, thus causing the car to have to sit very high in the rear. And the cage was, shall we say, "unique".
Many compromises were made, and a few bars added here and there.
All in all , it worked ok, but in the never ending quest for more speed, it was later decided that the front half of the car should get cut off, thus creating a full tube chassis.
After much trial, and tribulation, it finally made it down the track. But performance was less than expected, so plans were made for an upgrade to aluminum heads.
This is about the time we got involved. After George and I got together after a local car club meeting, he asked my opinions on the latest offerings of the TA Performance cyl head, and in general what I thought about the car. As gingerly as possible, I suggested we re-work the chassis, to create a suitable platform for a more powerful engine.
I had viewed the car at a previous race, and we had run it across the wheel scales, in an attempt to sort out his chassis. We were able to make the car go straight, but a few minutes of inspection, visually and with a tape measure, revealed some serious issues, and design flaws. The car sat way too high in the rear, and very low in the front. It also sat lower on the right side in the front.
Here are the pictures, taken the day the car was dropped off at the shop, and put on the chassis table. Speaking of which, in the shop, we have built a 16x9 foot table, that is perfectly level, and square. Along with that, I fabricated custom chassis levelers. These two pieces of equipment are absolutely required if your going to do chassis work correctly, and the lack of a level, flat surface is directly responsible for the problems this chassis had. It was built on a crooked floor, so it was crooked! You will see the value of the table and a level chassis as the pictures unfold.
Before:
Yep, that is what I thought... what the ...
After George explained that the X brace was not there initially, and the back seat was, some of the cage started to make sense. Well, some of it..
The first task was to get it level, and do a complete inspection, after casting down a chassis centerline and a line perpendicular to the centerline, for a measurement reference. With a level chassis, and these two simple lines, we were able to tell George more about his car than he maybe wanted to know.
In short:
The entire chassis was twisted 3/4 of an inch, the left frame rail at the rear wheel opening being higher than the right.
Although his previous builder stated he had built the car with 1 inch of stagger, we found none, but did fine the overall wheel base was only 111 inches, or an inch sort.
The mounts for the suspension in the rear were badly out of square with the chassis centerline, and were unequal distances from that line.
The car sat 14 1/2 inches off the ground, at ride height, when measured at the top of the rocker panel, just ahead of the rear wheel. It sat 4.5 inches off the ground, at ride height measured at the same point, just behind the front wheels. Yes, that is 10 inches of forward rake... eek..
And the crank centerline was too high, and the drive line angle was wayyyy to much, over 9* of rearward tip of the motor.
The access in and out of the car was horrible, the driving position way too close to the steering wheel, and the whole "feel" of the cockpit was, in a word, uncomfortable.
Here are a few pictures of the measurement phase.
Many measurements were taken, and everything was recorded right on the table, for future reference. All points were plumb bobbed to the table, and then measured both vertically , horizontally from the centerline and length wise from the perpendicular line to get a complete picture of what we had to work with, and how to fix it. Although only the front end is shown, this was done to every suspension point and mount in the car , and selected points throughout the frame.