B_Pay

I have new rotors and 4 hawk hps pads on each wheel. I have a SY3500 converter and can only brake stall it up to around 2200 rpm before my wheels start to spin. I'm getting very poor 60 foot times so I called Yank and they told me to stall it up to 3300 rpm.

Well I told em my problem and they suggested softer compound pads and told me to bleed the brakes. I'm not so sure this is gonna make a difference and I was wondering if I could put a proportioning valve in my brake system to increase the brake bias to the rear?

If possible, I obviously don't want to increase the bias too much where my rear brakes lock up before the front. Is there a way to calculate when this will happen, or am I limited to a guess and check?

Anyone with any ideas is appreciated.

mitchntx

iTrader: (14)

'98 plus F-Bodys use the PCM to bias braking based upon speed sensors used by the ABS.

The PCM will compensate for any mechanical biasing attempted. These cars wheel hop really bad under HEAVY braking. It has been thoroughly investigated ...

Louis

iTrader: (7)

Yes, you can.

try wilwood, or Tilton. I think that summit may even carry one.

Mitch, the Bias valve will still help. You can take away front, or add rear. It is a guess and check method though.

At a stop, the ABS cannot do anything if the wheels are not turning.


Louis

Louis

iTrader: (7)

He is talking about staging

trackbird

iTrader: (4)

True....but anything done to the car for staging sill probably be there for the "panic stop" at "the big end" of the track. I'm not sure of the safety of such a thing. A rear line lock? (I really dont' like that one either....but maybe). I'd be afraid to stop from 120+ mph (or even 100) with lots of rear bias....

Just my thoughts, I could be wrong.....

mitchntx

iTrader: (14)

DOH!

B_Pay

A rear line lock sounds interesting but the pressure wouldn't be increased, just locked in place from what I understand. I need to increase the pressure applied to the rear brakes. Is there a way to increase the pressure using a line lock device, but only while staging?

I understand a trans brake would be best, but I haven't heard of one for a 4L60E.

trackbird

iTrader: (4)

I agree that a rear line lock wouldn't increase pressure...I was thinking out loud (in type?) and was looking at safety. If you could generate enough pressure and line lock it, you could reset the adjustment before launching (so your brakes work normally at the end of your run). I was just considering the danger of too much rear brake at the end of a 1/4 mile blast (wheel hop, instability, it may try to spin???). Those were my concerns....otherwise, you may need more converter (less effecient to get your stall you want). Just my thoughts....

trackbird

iTrader: (4)

One other consideration. When you "foot brake stall" a converter, you preload the rear suspension. If you are using any kind of "trick torque arm or relocation brackets" you will lose some of the benefit of those parts. They depend on the acceleration of the car to rotate the axle and lift the chassis to plant the tires (tires rotate forward, the axle "torques" backwards and the suspension lifts the body). When you have the brake on and the converter loaded, you have already started to rotate the axle and load the suspension. Also, if you simply "mash it on the amber", you will get a "flash stall" of the converter (which may be higher yet), as the engine accelerates up in rpm until the converter "catches" it (thus launching the car). Also, the Foot brake technique can generate alot of heat in the transmission, and autos don't like heat.

You can do whatever works best for you, but you may want to make a few runs by simply "standing on it" and see how it runs. Once you get the tree timing down, it may work better.

Just my thoughts....

B_Pay

I appreciate your input trackbird, it seems like this is an odd situation that most LS1'ers don't encounter.

I started thinking that maybe people are getting better short times with the SY3500 and 3.73 gears than I because they have headers or a cam. Maybe less torque down low causes the torque converter to hit harder at the launch. Maybe this should be a question for the drivetrain forum.

B_Pay

I did as you just suggested. I got my best 60 foot by flashing it from idle.

I tried brake stalling at every rpm with my combo. That's why I feel like stalling it higher will benefit me, since every other way didn't do any better, plus Yank suggested it.

Note, I didn't get any spin on any method, idle or stalling it up as high as I could. My car also traps 108 with just a lid and cutout, so power isn't unusually low.

Louis

iTrader: (7)

Now that I think of it, Just go into the auto forum, and ask what people with the SY3500 are brake stalling up to! 3300 seems high for a 3500 verter.

trackbird

iTrader: (4)

Lou's right. (I missed the big picture...it happens). 3300 does sound high for a 3500 stall. Interesting....