Happy and sad at Sumerduck 1/8mi
 

Well, I went to Sumerduck last thursday for test and tune, 1/8 mile track to test the ole 69 firebird with the troublesome 537motor. Could not floor it off the line for blowing the tires away, so I went as soft as I could with the 255 M/T drag radials and got it to the floor in second gear. Ran 2nd gear almost to the stripe, shift to 3rd and cross the line. 6.70 at 104 mph. This car weighed 3735 with me in it BEFORE I put a 12 point cage in it and have not weighed it since, so it is heavy.
I did try a pair of slicks while there but when I launched it, it felt like I was on a trampoline, the rear jets do not have extensions on them and I guess the jets were getting exposed to air at that acceleration rate. The car would launch and fall, launch and fall about 4-5 times and I ended up with a 1.65 60 ft.
My question is, what times should I run if I take out the 3.50 rear gear and replace with a 4.11 and replace the 255 DR and replace with a slick or 275 DR with a better bite?

Current combo
537 tiger headed 1050 dom on low profile intake built by me
264-270 roller
t400 trans 10" continental convert 3800 stall
9" rear with 3.50 gears
slide-a-link traction bars
Chassis dyno 626 hp at 6800 and 518 torque at 5400

Happy I didn't break anything but sad with the times

Grandville thanks for the post about the attention to detail on the rear shackle bushings, I will try that also.

Steve

Congrats on getting it out and running it.

Sounds like some chassis work is necessary now.

If you're not going for a 'street tire' class, I'd used a set of slicks to start making it consistent.
Probably need some shock work and with that kind of HP, probably need a better rear end setup.
(don't know much about slide-a-link)

Binding is probably a consideration.

The car sounds like it was 'porpoising' with the slicks.
(usually from front and rear chassis setup wrong)

I would think a higher stall would help more than the gear change also.

Time for some test and tuning.

:)

I haven't been to "The Duck" in a while. How is the shut down area? I was always concerned about stopping my whale (4,100#) there at 6.40's.! Your car's not that much lighter. But I also had 4 drum brakes then..

Do you have extensions on the vent tubes? Piece of rubber hose with hole in top will do. If not, could be sloshing fuel out of them on launch. Just a thought. You didn't mention what shocks you have. Maybe have some adjusts for the slide a link? I'm not up on them.
Did you launch from idle, or bring rpm's up? Leaving from idle hits the tires hard and blows them away. More rpm's will soften hit. Just throwing things out there..;)

Have to catch ya sometime around the neighborhood..
A buddy goes there now since OD shut down. Should have GP out in a bit, hopefully.

Do you have inner tubes in slicks???

A friend had a similar problem, removed inner tubes, problem went away...don't know why....

Got Herb Adams Adjustable shocks in the rear(12 years old when I used to autocross the car) I did just install QA-1 coilover shocks in front with 450 rate springs.
Slide-a links are similar to caltracks
No tubes in the slicks
Left just over idle and got to the floor at the top of first
60man, we definitely need to meet up at a track somewhere, could be fun, Might go outlaw racing at Capital a time or two. As far as "The Duck" bring good brakes because you gotta stop going downhill as you know.

Steve

Stop going downhill, while turning left at the duck!

I heard those Coilovers really arent good for something til your up near 1000 hp, not enough transfer for the lower hp cars... You have plenty of cubes I wouldn't go to 4.11! Sort the suspension out first, get it hooking , then see what the engine wants or needs for gear. Its all out the window til u hook.

just ordered manual brake kit to replace the stock power brake set up so I can stop at that track. My buddies and I usually rent do a track rental at MIR once or twice a year, much better track and longer.

Grandville, the motor hp curve does not noseover till 6850 rpms, so I think more gear would help and since this is a street driven car, maybe Santa will bring a gear venders od next year ;)

steve

True you make power up higher which should be more mph, but if your 60's weak now from lack of traction, it will only get worse with more gear.You will have even more SLR to try n plant all that torque.it won't show its true potential.

I just got some 10" draglites for the rear to replace the 8" wheels on there now and will get some 275 x 60 or 50 m/t DR (whichever fits better). That should help it grab. Probably will do one thing at a time. My goal is 6.20-6.40 1/8 mi et and high 9.s 1/4 mi. Hope I get it. Your car runs pretty hard so I'll consider your advise.

steve

The QA-1 replaced the factory springs also?
(your front end modified?)

I'd check for shocks topping out.
Usually the 'porpoising' is from a mis-match in springs front to rear.
(harmonics - like too stiff front)

Try some softer springs on front plus check for shock topping out.
(or limit the travel of front for a couple passes)

Also what's pinion angle?

Lots of things to try that don't really cost much to see what works.

:)

Video would help a lot too , see what its doing, u need to make sure u have plenty of travel for ext in the back , so your not topping them out. I run 7" stroke DA Afco's and use 5.5 for the EXT. Watch my video in my thread n u will see how much the car seperates on the hit.

Yes....make it to Capitol. One of Capitol's owners is a Pontiac guy. They sweeten the pot for us. Purse is usually pretty good. Especially the season final.. Don't have to run points to run with us. Also started with Buy Backs this season. Ladder after 3 rounds..

so what do y'all think the potential is?

Absolutely... at this level a tenth improvement in 60's is worth 2.5-3 tenths on the other end!!

Even if you get car to hook you can still find notable gains in chassis adjustments. The "goal" is stay hooked and strive to have all motion moving you forward, not up or sideways or twisted etc.. You wont ever reach perfectly flat level launch/run and perfect traction but...the closer you get to that and maintain traction the quicker you will get.

Video is your best tool if used by someone who knows where to focus... you'll find one fix and see something else... some "fixes" that didnt work early on work great later so dont rule things out. ONE adjustment/change at a time or you will mess yourself up.