Help pick stall speed.

[ss dave]

First, got a 383, approx. 425-450 hp, same tq, race built 700r4, 3.73 posi. Burned up the first converter, got new converter but stall too high, approx. 3100-3200. Allowed one converter stall change. This converter warrantied to 1100hp. Can't get tires loose when shiftiing form 1st to 2nd and even difficult in 1st. What would be a good stall for my street ride? Thanks

[ProStreet R/T]

So with 450hp you can't spin the tires at all?

RPM range are you running in? I'm guessing 2500-6k max? What rpm does is peak torque made at?

What makes you think the 3k is too high?

Personally I favor a high stall converter on the street. My truck for instance makes just over 400rwhp N/A with 6200 rev limiter. With 3.92 gears, 29" tall tire, and weighing in at 4400lbs with me in it, i'm running a P.I. 3400 and it's my daily driver.


If it's too loose you might have it restalled to 2800 but personally i'd leave it alone. Sounds like you may have other problems too look at.

[ss dave]

Example, WOT @ 6K in 1st, shift to 2nd- no spin, the motor has plenty of low end tq and power, est. peak tq 4500. The first converter was rated at approx max hp 450 but had a stall at prob. 2500 and could get the tires loose. This converter never seems to lock up solid except with OD. Motor hits fine, replaced clutch pack in tranny last convert change. rest of tranny good, rear end- no problems. My mechanic states that the converter is absorbing the tq and not transfering the power. The converter is from a reputable builder, 9.5" Precision Industries.

[ProStreet R/T]

P.I. is the same setup i'm running, very nice converter from what I have seen.

Have you tryed calling them about it? Their tech support is very good and should be able to help you out.

The converter shouldn't "absorb" the torque at all. Does it feel soft when you nail the throttle from a stop? Like it stalls up then just takes off once you reach a certain rpm?

How firm does your trans shift? With peak torque at 4500 it should respond much better to the 3k stall than a 2.5k.

Dumb question, but have you checked the fluid level?

[slowcamaro]

Cam specs?

[ss dave]

Checking on the specs for my Isky cam. Fluid OK. Soft from start. My mechanic has the tranny shifting as firm as he felt comfortable with (he stated as firm as he would allow) It has good accleration but no "pop" when shifting to 2, it just feels like a Buick LeSabre, smooth but no tq. From my first converter to this one it feels that I've lost about 50hp.

[Steve Chryssos]

I don't see a torque converter problem at all. Stall speed defines slippage. When foot braking, a 2500 rpm converter will slip from idle to 2500 rpm. The reason for this slippage is to let the engine build rpm so that on launch, your engine is in it's power band.
So at 4500 rpm or 6000 rpm or any number above your actual stall speed the converter should not be freewheeling.

Now published stall speed can vary from actual stall speed. For example, if you put that same converter behind an engine with 600 ft-lbs of torque, that 2500 rpm (advertised) converter will actually stall at a lower rpm. But figure that with 450 Ft-Lbs of torque and 268 degrees of advertised duration or less in a 3400-3500lb car, a 2500 rpm converter should stall right around 2500 rpm.

Before you make any changes or seek any advice, you should perform two simple tests: A foot brake test and and a standing start launch from idle without the brakes.
The foot brake test will tell you at what rpm the converter stalls. Apply brakes (stand on them--pump a couple times beforehand if necessary) and bring the rpms up. The rpm where engine torque tries to overcome the brakes is your stall speed. If, like you say, the thing does not reach stall speed and the revs keep building, you may have a converter problem. If the car tries to get out of its own way or the tires start to break loose, you found your true stall speed. Don't make a habit of repeating this test as it does build heat.
Next, try to find your flash stall rpm. This number is higher than your stall rpm. I wouldn't even bother recommending this test except for the fact that it sounds like you really enjoy mashing the go pedal! With car at idle, take foot off brake and instantly mash the throttle. It's hard to tell, but there should be an rpm where the car really surges forward and/or the tires break loose. Of course, if you have a carburetor or fuel map problem, finding flash rpm can be difficult. And you need to watch the tach and maintain car control and get ready to shift. Again, if the engine is zinging up to redline and the scenery is not blurring, you may (may) have a converter problem like a bad stator/one way clutch. Then again, you may also have a carburetor problem resulting in very low torque output (for example). But at some rpm, the tach should sweep less quickly while the car accelerates more quickly (load).

Again, higher stall speed is just a way to slip the engine rpm so that when stall does occur, the engine is within the meat of its powerband. The foot brake test will tell you at what rpm stall occurs. I'm thinking the problem is in your transmission or engine, but try to determine stall speed first.

[ss dave]

Thanks for all the info, PI has been helpful. Going to try a converter change to see if it is the converter.