Thread: Choosing a converter

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Hey, i am putting an olds 455 in a 79 trans am and i am getting a new TH400 for it but im not sure on how to choose the right converter. How do i know what stall converter to get? any advice is welcome

How do you intend on using the car? How much cam is in it? Gear ratio? If it is just a stock motor and you don't want any extra out of hole launch, a stock convertor would be fine. But if you have a hotter cam, intend on driving a little harder, and want more kick out of the hole you might step up to maybe a 2400 or so.

We have the same motor in my Sons rpu and at first used a 2500 but it wouldn't let the cam do it's thing out of the hole, so we are moving up to a 3000 stall and going from a 12 incher to a 10 incher. That should make a lot of difference.

Don

Welcome to CHR

Rear end ratio has a lot to do with stall speed as well. In that vintage (1979-1981), automatic transmission equipped Trans Ams and Z-28s came from the factory with 2.41, 2.56, or 2.73 rear end ratios depending on engine/transmission combinations. I believe there was an optional 3.23 positraction with the 400 HO package. Four speeds were typically 3.08.

Not knowing what your rear end ration is or how long your cam duration is it would be difficult to come up with "exact" numbers for the stall speed. In that the car weighs 3550 pounds and the 455 will add a few more I would agree with Don’s advice to go somewhere between 2400-2600. If you have the 3:23 posi, go 2400 – if you have 2:73 or 2:56 go with the higher stall speed.

Give us some more information, i.e., how you’re intending to drive the car, engine modifications, and rear end ratio for a more “precise” answer. While I also agree that high tech is filtering down to hot rodding, converter selection is not a science, rather a combination of “what-ya-got and how-ya-want-to-launch”

Regards,
Glenn

Big thing to remember is the smaller the converter, the more heat the trans will make. Having a good tranny cooler is key to any transmission and NOT the one connected to the radiator.

weight of car comes in to play some what and go.s along with rear gear cars like dons need more stall as there is less mass to move less mass =more stall

I too am looking for the right torque converter. 32 Ford Coupe, Summit GM-19210007 350 crate engine w/330HP, Summit TCI-311038 TH350 trans, 3.0 rear end, looking for a smooth drive from 0 to 70mph. May want an impressive jump off the line every once in a while but not building a race car. My thoughts are 2000-2400 rpm stall speed. Any advise.

Originally Posted by HarryH

I too am looking for the right torque converter. 32 Ford Coupe, Summit GM-19210007 350 crate engine w/330HP, Summit TCI-311038 TH350 trans, 3.0 rear end, looking for a smooth drive from 0 to 70mph. May want an impressive jump off the line every once in a while but not building a race car. My thoughts are 2000-2400 rpm stall speed. Any advise.

Do you have the torque/hp curves for your engine, even predicted curves that might have come with it? If nothing else I'd be looking at a converter that gets you up on your torque curve before stalling out if you're wanting the line jump. How tall are your rear tires?

back tires are American Racing 10" and stand 28" tall. 350 cubic inch HO with approximately 9.1:1 compression, 330 hp at 5,000 rpm and 380 ft./lbs. of torque at 3,800 rpm.

Originally Posted by HarryH

back tires are American Racing 10" and stand 28" tall. 350 cubic inch HO with approximately 9.1:1 compression, 330 hp at 5,000 rpm and 380 ft./lbs. of torque at 3,800 rpm.

The 28" tall tires are not extreme. More critical than peak hp and torque is where the torque comes in as you're accelerating under load. For example, my torque curve comes up quite steep from 1000rpm, and is nearly flat from 1800rpm out to 5200rpm where it starts falling off a bit. That means (to me) that if I were running an automatic, a converter with stall in the 2400 range would be a pretty good fit. Do you have the curves, or just peak values?

THE best thing you can do is contact a couple of converter manufacturers. They are going to ask for all of the info everyone above is asking and they can give you an actual answer. Not to knock anyones knowledge here but it is my experience to go direct to "the guys who know" when purchasing a converter.
Mark

For a street car, remember that more stall = more heat, too, and heat is a killer of automatics. Not such a big deal on something light like a coupe, but nevertheless hi stall converters on the street can lead to some real heat issues. I'm with Mark on calling the companies who make the converters to get something right for your car. On the rare occasions I actually use an automatic transmission, I write down all my engine and car information, take it to my pal Jim--who builds automatics for a living, then Jim calls the converter company he uses out in Colorado and a week or so later here comes the converter I need!!!! On the drag cars, whole different animal then what works on the street, Roger and Rodney are both running Coan converters and glides now--and I still have my 5 speed with a Soft-Lok clutch--so whenever we're together we always have something to argue about, consistency vs. lots of gears to keep it in the power band!!!!!

It seems every time I've put in a hi stall converter, I've been yearning for more. However, in my latest endeavor: 383 Summit crate motor wit 700 R4 Summit trans, they chose a 3000 stall and it was immediately obvious that it was too much. Swapped in a 2400, and It's a world of difference.

I have a 30 Coupe, wt. approx. 2200lbs., smallblock, roller cam, big heads, T350 worked trans, using a 3200-3500 stall Super Streetfighter, w a 3.89
(3.90) gear. Runs well, shifts good an firm, and will pull extemely hard off the line....28" tall tire, going to a 30"