[XLR8STEVE]

My Pontiac Friends,
This was one of my better launches from Drag Week this month. I had real trouble hooking all week.
29.5x10.5 C06 Compound Hoosiers at 13psi
4.10 gear
Double adj all 4. out of 18 clicks (18=full stiff)
Fronts 7 R 18 C
Rears 7 R 14 C
Stock locations on 4 link all adjustable arms
3.5 Neg Pinion angle
Anti roll bar and control arms no preload
2 STEP was 4000 on this launch

I was up to 5000 2 step and all in between
I tried 12 lb and 11lb in slicks - wadded up
I tried full 18 C on rears and 3R on fronts
All resulted in spinning.

60' on this launch was 1.48 my best all week. Hitting 135-137 mph in quarter.

Any help is appreciated. Thank you!

Youtube link:
https://youtu.be/-Xgc-nlqbUc

[Keith Seymore]

My car is an automatic, so take this with a couple grains of salt: but - I gotta believe those stock suspension attaching locations are not doing you any favors.

I would suggest anti hop bars (or the equivalent) to move the rear suspension instant center location down and rearward, providing more separation (and therefore "plant") of the rear tires at launch.

I'd have to dig out my notes but I believe I have the fronts of my upper control arms dropped 2" IIRC.

Chris Alston refers to the relationship between the IC location and the center of gravity as "percentage of rise", but the guys I hang with just describe it as a linear dimension forward of the rear wheels and a certain distance off the ground.

K

[Keith Seymore]

Also - I'm running 18 psi cold in my Hoosier DR2's.

They hooked even when worn out and with the cord showing.

K

[wolf]

I don't see much wrong with the chassis reaction, but it does look like there's way too much clutch.

[Skip Fix]

Slipper centrifugal assist clutch?

[Mike S]

I have a 67 but basically the same suspension. I do have an automatic and launch with a trans brake. I always had a tuff time hooking slicks consistently. I switched to 315 radial and have no problem now with no changes to my suspension. It usually has 1.34 60's and traps at 133 for 10.00.
All stock suspension but aftermarket arm. I have them in stock mounting location except for the back of the lower bar, it is lowered 1" on the rearend. Double adjustable on the back, set at 6r/14c. 150lb springs. I have the car as low as I can get it. Up front is all stock including the front shocks.
I have 4.10 gears and weight 3500lbs. Launch at 3800.

I add weight to the trunk to slow the car up and found the more weight I add the better the 60'. My last race I had 300lbs in the trunk and had a 1.32 60' to go 10.00. With no weight it will 60' 1.29.
Might be a band aid but add 100lbs as far back as you can get it.

[XLR8STEVE]

Great stuff guys,
Keith I have anti hop bars from Dick Miller for this rear. I took em off because with the old motor it was too much. I can try them again. I also have links to lower the rear lower arm mount points. Gotcha on pressure. I was going the wrong way down to 12,11 psi.

Keith and Skip I have a hydraulic system with a Mcleod RXT 1200HD. Very much on/off. I am looking into a launch control solenoid I can control with the Terminator X to be active 0.X seconds after the 2 step is released by the clutch switch. Tricky stuff to set up but I am sure once i get it it will help with the initial shock.

Mike right on, I put a full tank of gas for this run vs 1/2 most of the time. weight helped.

[Skip Fix]

I think a lot of the SS stick cars use a centrifugal assist clutch.

The asphalt car I had for awhile had a hydraulic throwout bearing that was on or off.Hard for me to even move around the shop

[blueghoast]

Try another 4 degrees neg pinion angle I have mine at 10-14 for street
racing and no vibration what so ever I footbrake and spray 300 NOS
shot too. Pinion angle can be your friend. Try it first just to see if works.



GT

[Keith Seymore]

Originally Posted by blueghoast

Try another 4 degrees neg pinion angle I have mine at 10-14 for street
racing and no vibration what so ever I footbrake and spray 300 NOS
shot too. Pinion angle can be your friend. Try it first just to see if works.



GT

Except I imagine your car is leaf spring.

His is factory four link, so dramatically less (essentially zero) pinion motion due to spring wind up.

K

[brut4s]

Check with guidos on here Facebook or In w youtube. He's running a manual Trans and doing drag and drives. On you tube he goes over his clutch setup

[blueghoast]

Originally Posted by Keith Seymore

Except I imagine your car is leaf spring.

His is factory four link, so dramatically less (essentially zero) pinion motion due to spring wind up.

K

No mine is stock style 4-link suspension. No-hops adjustble upper
and solid lower trailing arms with solid bushings

GT