i just got a basic rebuild done on my 91 700r4, he put better servos in it and a bigger 3-4 clutch pack and did something with the pump and shift kit, my question is now i need a converter and i dont know what to go with

the two things i cant decide on is what stall and what brand, i cant decide between 2000 or 2500 stall, i want a good launch, but i dont want bad mileage on the interstate, i have 3.42 gears btw, i was thinking the tork master 2000, it says between 1900 and 2100 stall speed, or should i go bigger, im also thinking about getting a xe268h cam, but dont have it yet, all i have now is a performer cam, so what converter should i go with? also the guy who built my transmission said that an s10 converter would work well because they have a slightly higher stall than a stock one, but i dont know if i should get one of those or a brand name converter, what should i do?

 

anyone?

 

What motor do you have? What heads? What exhaust and what other mods?

There's AHELLUVALOT of difference between the "Performer" aka "RV" cam, and ANY modern performance-oriented grind. That's a MASSIVE step. In fact, 2500 RPM stall probably wouldn't be enough, if you have a 350; and it would be altogether too little, if it's a 305. Plus, it'll require changing your valve springs and all their hardware, at a minimum; and possibly even doing machine work to the heads.

On the freeway, the engine will be above that stall speed, and the TCC will be engaged ANYWAY; so the stall speed won't be an issue at all.

The S truck converter is loose. Not only does it have a higher stall, but also, it NEVER hooks all the way up behind a V8, because it's intended for use behind a 6-cyl with no torque. Bad idea. Works OK in a light car with a small (low-torque) motor and some gear, but not a heavy car like these with a highway gear setup like 3.42s. You get, AT BEST, what you pay for, in a converter; so, if you pay the least, you get AT BEST, .... well, you do the math.

 

woah, woah, its a 350 with about 9.6:1 comp, camel hump heads, edelbrock performer cam intake and 600 carb, and its got headman lts with no cat and duals, i know its a big step but im just gonna order the whole k kit, and get new push rods and rockers, right now its all pretty mild in the cam area, and im gonna step up to the xe268h cam after a few more miles on the motor, and it says biggest cam on stock converter, so im sue it would like a 2000 stall,

so what your saying is stall speed matter nothing at all on the highway since it will be locked up anyways? i guess i never thought about that, so i think ill stick with the 2000 stall, that sound about right?

 

No....

The idea is, you get a stall speed that lets the motor run in its ideal RPM range, when it's in a power situation; but that doesn't matter on the highway, because the TCC is locked up, which essentially means that the stall speed is ZERO under those circumstances. Just like a manual trans: there's no fluid coupling at all, it's ENTIRELY mechanical.

I'd suggest something in the 2800-3000 RPM range.

 

2800-3000............? why? thats half way throguh my power band, the cams powerband is 1600-5800, so if i had a 2000 stall it would come in just after it started making power, not 1200 rpm after........

im talking about getting the comp cam, xe268h, maybe you got it confused?

http://store.summitracing.com/partde...2&autoview=sku

 

No; I'm pretty easily confused, but not that bad.

Think about your RPMs, as they are now, with the cam you have and the gears you have. Do this thought exercise: you're sitting at a stop light, and you floor it, watching the tach. Or even, just go get in your car, and do it.

Quick: how long did it take before your RPMs reached 2800?

THAT'S why you need a higher stall. Basically, your motor spends almost no time at all below that ANYWAY, except when cruising; which the TCC takes care of. No sense in pinning it down there and forcing it to struggle getting up to speed.

Comp's recommendation (2000 +) is BARE MINIMUM, which is not the same thing as OPTIMUM. It is also intended for people with NON-LOCKUP transmissions; you can't go quite as wild in a T-350 car, for example, because you absolutely MUST be above the converter stall RPM while driving around in "cruise" mode, or you WILL burn up the trans and waste a shameful amount of fuel.

I had that cam's next bigger brother, the XE274, in a 400, with 186 casting heads, for a while. I still have one of its near relatives, a XR264HR, in my car right now. Trust me, I know EXACTLY what those cams run like. That combo (350/XE268) will produce virtually the same torque vs RPM curve as the 400/XE274 combo, the numbers will just be lower. In the 400, the chassis dyno showed that the torque rose rapidly from 2500 to 3000, and then rose much less rapidly to its peak, at about 4400 or so. That curve tells you where you want the converter stall: in a street car, right at the "knee" of the curve, where the torque reaches its long-term average kind of value, and is up above the "suffering " part of the curve. In a race car of course you'd want it higher, up near the actual peak torque RPM. But I doubt that would be a good idea in most people's street cars.

The stall speed of a stock 700 converter behind a 350 is about 1600-1700. A 2000 RPM stall would hardly even be noticeable, especially with 3 series gears, because the vehicle will pick up speed quickly enough that within a half second or less, you'd be past that anyway. 2500 would put it right at the point the motor begins to make significant power. 3000 would put it within 10% of its peak value.

 

ok, i see what your saying, but i was just a little confused because it says about that 268 cam, biggest cam with stock converter, and i thought stock was lower than that, even then, 2000 is still slightly larger than stock so i figured it would be ok, maybe not thought

 

I run a 355 with a Comp XE268. I have a 2200 stall in mine. From what little I've driven the car, I like the stall. I'm getting a new transmission installed in a week or so when it comes in. I'll let you know what I think about the stall and how it runs. I've thought about a higher stall, but I'll see how my 2200 does behind the new transmission. Oh I bought the stall from Bowtie Overdrives for $175.