Improving 60' times, third gen f-body

[Dan Fahey]

Originally Posted by TonyB83

I'm looking for improvements in the 60' and I'm told this is the place to ask. I'm sick of the f-body specific forums so here goes-

Car is a '90 Firebird, a bracket car. Small block, TH400, 3.73, 3500 converter, 28" tall MT radial tire. Runs 10.80-10.90's at 124mph with 1.44x 60'. Suspension consists of 90/10's in the front with Moroso trick springs, 50/50 in the rear with V6 springs, Spohn torque arm and tubular LCA's.

The 60' can be inconsistent at times and I'm looking for ways to improve. I've been considering switching to adjustable shocks or coilovers but need to learn more before I do. Can any of you help point me in the right direction?

This may not be the best, but it's an iPhone video my wife took last weekend.

Seems you have the right stuff.
Consider adding weight to the back, no cost.

The Torque Converter does not need a hard STR like a Stocker.
If you have an computer electronic system.
Retard the Launch Timing to soften the hit.

Get rid of the Radial Tire. Back to the standard Slick.
Radials are a cause of inconsistency.
They work when they work usually with well prepared tracks.
They are not at all forgiving when the track prep is not spot on.

D

[Ed Wright]

I have never had a bias tire hook as well as a radial on any track. I've heard thAt repeated, but it has not been my, or any of the guys I race with's experience. I was away from this for a while when I went dirt circle track racing for about ten years. Our local track prep is a bit hit. & miss (more miss than hit)
I started out running bias tires because that is what I knew when I quit to go roundly-round. Pete Peery put me onto the radials. I ordered another set of wheels, and some same brand, same size radials. Easy 2/10 quicker in A-B-A testing, and the bias tires were hooking just fine that night. Tested that a couple more times when the track prep was not so good. I have never found conditions my radials failed to hook at least as well, or better on slick tracks. They have been at least as consistent also. As far as I can see, only most stick cars like bias tires better. Of course, they don't want stick cars dead hooking. Even Pro Stock cars like to turn them over a revolution or so on launch.
Things I would look at are: Softer rear springs (just enough spring to hold the car up with coils) soft front springs (I would use no more than 275lb front springs on a Camaro. Also taller rear tires make more difference than wider. Loosen up the front end. If you knock your ball joints loose, then raise a control arm (not connected to the spindle) and it doesn't drop on it's own, it's too tight.
How to do some of this would take up too much room here. PM me if you don't know how to do some of this.
Hope this helped.

[TonyB83]

Thanks for the replies.

Ed, would you recommend going to coilovers on the front? I believe that will allow for more spring options.

It's hard to tell because of the video's quality, but it looks like the front end comes up briefly, sets down a bit before coming back up. Almost looks like a 'bounce' Could this be causing a problem?

How does the LCA angle affect performance? I do have LCA brackets which will change the IC.

[MAURICE BLENDHEIM]

Tony… What engine displacement, cam, intake, head and carburetor? Does the TH400 have stock rotating internals? What determined your choice on 3.73's. MB.

[TonyB83]

Thank you all for the replies.

the converter and gear sound like the makings of a street/strip car and not a bracket car. Tell us about the engine...heads, manifold, camshaft, compression, etc.

3rd gen f body bracket cars weighing 3100-3200 lbs. with driver run easy mid to low 10's with nothing special small blocks, power glides, 8" converters, 4.56 gear and 10" tires

Originally Posted by MAURICE BLENDHEIM

Tony… What engine displacement, cam, intake, head and carburetor? Does the TH400 have stock rotating internals? What determined your choice on 3.73's. MB.

383ci, Comp XE288HR cam, Edelbrock RPM Air Gap, Holley 650 (modified, flows 740) AFR 195 heads (ported, 2.05 valves), 10.9:1 compression. Stock trans internals, just upgraded soft parts. Went with a 3.73 mostly because it's street driven but I wouldn't be opposed to going to a 4.10.

[1320racer]

so it is a street/strip car.

That said, it's all about compromises, what you are willing to sacrifice in drivability for quciker ET's but without question you need more converter and more gear and the right converter from the right manufacturer won't give up any street manners.

[njk53]

I think the 3:73 gear and converter are the issue. I would think a converter in the 4800-5000 range and a 4:56 gear would do the trick. What RPM are you turning the motor through the lights? Depending on trap RPM you may be able to stand even more gear.

[Ed Wright]

You might ask some fast Stocker guys. I never put those things on my car. I think they are just wrong. I see kids using those on ls1toke.com.
When I was bracket racing my car on 9" tires, I could hardly keep it off the back bumper on a good track. Ran mid-high nines that way. Usually 1.30-1.32 in 60'.
I used PeteZ bars then. Had too much tire-body separation, but I lived with it until I bit the bullet and had Eastexas Racecars work their magic.
I have had QA1 front shocks, could not get them ajusted stiff enough either direction. Never stopped bouncing on landings. Then went to AFCO fronts, still not enough adjustment either way. Finally bought a set of Santuff shocks. Some of the best money I ever spent. I can make it stand straight up, or barely carry them off the ground by just adjusting the front shocks. No more bouncing on landings either.

[countrypuppy4865]

I would say more gear (4.33) and convertor(around 5000 stall). A good set of front struts from fastshocks.com. Definitely stick with the radial (go with 29x9 30x9 on 10" wheel or 30x10.5 on 12 inch wheel). I always find radial more consistent. S and w has a nice anti roll bar setup. On my firebird, I have stock rear suspension single adjustable shocks s and w torque arm and frame connectors and anti roll bar. I have been 1.21 60ft going mid 9s with 30x9 Goodyear tires. Remove weight off front and run with 100-150 lbs in trunk.

[Ed Wright]

Originally Posted by countrypuppy4865

I would say more gear (4.33) and convertor(around 5000 stall). A good set of front struts from fastshocks.com. Definitely stick with the radial (go with 29x9 30x9 on 10" wheel or 30x10.5 on 12 inch wheel). I always find radial more consistent. S and w has a nice anti roll bar setup. On my firebird, I have stock rear suspension single adjustable shocks s and w torque arm and frame connectors and anti roll bar. I have been 1.21 60ft going mid 9s with 30x9 Goodyear tires. Remove weight off front and run with 100-150 lbs in trunk.

^^^^There ya go!