[Gary H]

Took the car out for one last time to test n tune at Gainesville. The video's not the best but I wanted to get some opinions of the way the cars leaving so I can work on it during the off season. The 60ft on that run was a 1.35. 1/8 mile time was a 5.96 @ 115. http://youtu.be/ysrZRgOSa8E

[SLICK1]

You either have no anti roll bar, or a lot of chassis flex, is there a full cage in it?

[SLICK1]

You could use more convertor too!

[warriors revenge]

you never said what you have for rear suspension/shocks, pinion angle, preload etc... in the car? yes put an anti roll bar in the car, make sure its a good one.... also from the video it looks like it was smacking the tires hard and feathering the track (didn't look like tire shake, but not far from)....may have just been the video... you may want to try more air in the tires and or a stiff sidewall??? looks like maybe it was trying to drive over the bulge
kal
www.xtremefabrication.com

[warriors revenge]

bitchin car btw... also is there a motor plate in the car??

[Gary H]

Thanks for the responses so far. No motor plates, just traditional motor mounts. Car has a 4 link and coil overs in back with narrowed 9". Factory suspension in the front with adjustable shocks. The convertor is around 5000 flash stall and I'm running a glide w/4.30 gears. Tires are 10.5W X 33's. The car always leaves straight but does lift the left more so than the right.

[Gary H]

Also, full rollbar in the car and I'm running 3 degree neg. pinion angle

[MCronkGTO]

Gary,

I am no chassis expert but there is something strange going on. If you listen to the convertor / RPM and watch the rear of the car, initially the driver side lifts up and then as RPM comes up more it squats down right before launch. The trunk lid shows some twisting going on as it shows a big gap as the car launches.

Are you footbraking the car or leaving on a tranny brake? I would not expect to see so much movement in the rear of the car before launch if you are using a tranny brake.

I had my 4-link set with no preload. I had my weight in the driver seat and had the links adjusted so you could slip the front bolts in and out easily (neutral).

I would make some basic checks first. Make sure the housing is centered on the frame rails and not "cocked". Look for any "odd" stuff i.e. shock settings, mounting points, etc...

I once had a similar problem that the car would lift the driver wheel way up and barely lift the passenger side and pull to one side hard. I tried every kind of adjustment and nothing made a difference. Eventually I started analyzing all the components closely and realized the passenger side axle tube had cracked the welds to the housing (12 bolt) and was rotating in the housing end!

Good luck!

[MCronkGTO]

Gary,

Also think your 60' should be better for that ET. My car weighed around 2,800 without me (3,025 with me in it) and had typical 60' of 1.36 but ran 9.80's @ 136mph.

Something else that comes to mind about front wheel drop is to check the travel limiters (if equipped) to see if they are adjusted evenly. Jack the car up on the center of front crossmember and see how much each tire drops and if even.

MarkC

[SLICK1]

Originally Posted by Gary H

Also, full rollbar in the car and I'm running 3 degree neg. pinion angle

How many points on this cage, does it go out to the front chassis, you could use an anti roll bar, and I'd have your convertor restalled to 54-5600! jmho. it runs well tho.

[Gary H]

Please explain a anti-roll bar and where it's located. It's a 10 point roll bar but the bar doesn't extend through the firewall area to the front end.

[BruceWilkie]

Pinion to driveshaft angle(not angle to ground) with a 4 link should be at 2 deg at static with driver as it would at the line...you can and may need to set it about .5 deg further nose down to account for deflection under load. If it actually wants more pinion angle you have a deflection problem to resolve. BTW front u joint angle should be 2.5 deg or less but never zero.

Hopefully someone can chime in on a good starting point for the bar positions/angles for your car... Keep in mind its important to maintain driveshaft to pinion angle if you change link position. Make sure you have sufficient shock travel.

Use a midplate and brace it to prevent fore aft movement!

[92GA]

It looks like you are keeping the chassis loaded with the brakes. Take your foot off the brake as soon as you set the trans brake, to take that preload away. Looks like the chassis is still moving when you leave.

My son started doing that early last season, and it upset the car.

[MCronkGTO]

I think you may need to have a good chassis shop take a look at the cage/frame. I would have expected to have the bars through the firewall to really tie the chassis together completely from front to back. Without those and with traditional motor mounts you may be twisting the chassis a good bit. Do you have the full overhead bars from roll bar to top of windshield and down through the dash to the frame? Has the cage ever been NHRA certified? From the video it looks like you are holding the car with the brakes. That can explain some of the "movement" before it launches.

Mark C

[SLICK1]

Originally Posted by SLICK1

You either have no anti roll bar, or a lot of chassis flex, is there a full cage in it?

Exactly what I suspected, add an anti roll bar, run the cage to the front subframe, a few adjustments, and you'll really see something!

[Gary H]

Originally Posted by MCronkGTO

I think you may need to have a good chassis shop take a look at the cage/frame. I would have expected to have the bars through the firewall to really tie the chassis together completely from front to back. Without those and with traditional motor mounts you may be twisting the chassis a good bit. Do you have the full overhead bars from roll bar to top of windshield and down through the dash to the frame? Has the cage ever been NHRA certified? From the video it looks like you are holding the car with the brakes. That can explain some of the "movement" before it launches.

Mark C

Mark,
Yes, the roll bar does go to the top of the windshield and then down to the frame, just doesn't go forward from that point. I very well good have been on the brakes without thinking on that run causing the movement just before the launch. Good point! Any good chassis folks down your way?

[92GA]

Before I spent any money at a chassis shop I'd make sure to stage the car with out standing on the brakes. That will upset the chassis even if you have the bars going from the cage to the frame horns. I went through this with my son last season, and our car will sit on 3 jack stands. 2 things could be happening when you stand on the brakes, preload of the chassis and the trans brake may not be locking the trans until you hit the throttle. I have a Hipster trans brake and we have to have it set, then release the foot brake, before the hit.

[MCronkGTO]

Gary,

It has been almost 10 years since I had any work done by them but the shop I used was The Race Car Factory in Stuart Florida. A friend had a 8 second street Turbo Buick (I actually drove this car on the street once) and he recommended them to me. I had them do several things over the time I owned the 78 TA. They added the front bars to the cage (did a very nice job going through firewall and not having to move or alter the custom tin work in the engine compartment), install a complete new rear housing including new 4 link and shock set up, anti roll bar, swap my gears and spool into new Moser housing, and add Aerospace front disc brakes. They were reasonable and always did the work right the first time. I also relied on them to "scale" the car for initial set up on the 4 link when I replaced the housing. I googled the name and they are still down there but have no idea if they are still as good as they were.

There are some good shops in Orlando but I personally have not had any experience with them. If you ask around at the track I am sure there will be some shops closer to you.

MarkC