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Old 05-19-2005, 12:08 AM
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Traction bar pre-loading

I have a 79 T/A with a 355 in it, 373 gears, performer RPM cam, weiand stealth intake, hooker headers, MSD 6AL, roller rockers and an edelbrock 650 carb. The last time I took it to the track she ran a 14.5... I figured most of the time loss is hopefully caused by poor traction since I had lots of wheel spin. I put a set of competition engineering traction bars on it in the fall. Supposedly these can be preloaded because they are the type that have J bolts that wrap around the axle. My question is, what is the proper way to do this? I want it to launch as straight as I can and some people have told be to preload it as much as possible to give the driveshaft the best angle. The instructions warn about broken axles if preloaded improperly. Are there any tricks to doing this correctly? Right now it's just trial and error and I still am getting some wheel spin off the line, which at times isn't a bad thing : ) . It's an automatic too with no stall converter in it yet so I'm not giving high rpm's off the line. Any insight is much appreciated.

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Old 05-19-2005, 10:51 AM
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Trail and error my friend, that's all you can do. There is no way to "baseline" this set-up because everytime you make a run conditions are going to be different. Changing air pressure in the tires and even the state of tune of the motor will all effect the outcome.
Realize also that as you tighten up the bars for racing you will need to loosen them back up for street driving. Getting them to tight effectively stiffens up the leaf spring to the point that there is no suspension left.
I would recommend checking out these bars... they are about the best thing you can do with a leaf spring suspension, are easily adjustable and just plain work...
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Old 05-22-2005, 03:40 PM
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I just picked up a set of those bars and havnt installed em yet.but i was reading over the instructions and it says use the wedge shims to get the driveshaft angle right.
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Old 05-22-2005, 06:09 PM
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Pinion angle wants to be 5-7degrees...that's the difference from the shaft to the pinion, not degrees from true zero. You need some air gap between the snubber and the spring eye. If the bar doesn't slap up hard on launch it won't load the tire. The front of that bar is the leverage point to plant the tire hard to the track. Since you have a stock convertor you may not notice the true effectivness of tried and true "slapper bars". As far as ride goes, you also need the air gap to allow suspension travel like astro says.

Back to pinion angle...many will tell you that pinion angle is the angle of just the pinion and nothing could be farther from truth. So, if you read say 2deg down on the driveshaft, and the rear axle reads zero then you have 2 degrees of pinion angle. Thge idea is to pull ther driveline to straight or as close to straight as possible under heavy load. For getting space betwwen the snubber and spring eye, don't be afraid to cut the snubber if you need to if the best angle/load set-up has it bound on the eye. It may even be a good idea to remove it untill your done then figure what you need before re-installing. Good luck and look to the obvious. Slapper bars ain't rocket science, just good ol tried and true hot rodding.
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Old 05-31-2005, 07:23 PM
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I think the recommended gap is like 1/8" between the snubber and the spring eye.
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