Who's running a automatic. c4

[Tom Wells]

dallas_,

Torque converter stall speed is a bit of science with maybe a pinch of voodoo

My engine produces probably 350-400 ft-lbs of torque at 2000 rpm, the car weighs 3100 pounds and it has a 2.88 rear axle ratio. It can spin the tires if I twitch my right foot at any speed up to and over 100 mph, using 200 wear rating tires which are pretty sticky -> Nitto NT05s.

The engine idles at 650 rpm so a low stall converter doesn't make the car try to go forward at stoplights very much at all.

So I guess the answer - as usual - for your case is: it depends.

You need to consider the low speed torque characteristic of your particular engine combo, the vehicle weight, whether the trans is 1:1 in top gear or has an overdrive, and its rear axle ratio.

I remember using a 3.55 behind a similar combo to mine; recall the top gear in a C6 is not an overdrive. It was awful - the tires spun at low speeds and the engine was buzzed up way too high at 70 mph. I switched that car to a 2.73 and it is a delight on the street and on the track.

A friend uses an AOD with an overdrive top gear (not sure of the ratio but it's common to almost all AODs) and a 3.55 and it works very well with a stock stall converter behind a 408 stroker small block with a moderate cam.

Look at some of the converter maker's web sites to see more considerations. Realize, too, that they may not understand exactly what you want, especially if they are drag race oriented. I kinda had to browbeat FTI a little to get them to make the stall as low as I wanted but I'm very happy with the result!

A high stall converter is needed for drag racing but not much else, unless you have a very small engine with almost no low speed torque. Driving such an engine on the street isn't my idea of fun, at least in a daily driver...

Have fun learning about this technology,

Tom

[RACERAL]

Dallas, hijack all you want ... the more info the better

[dallas_]

Thanks for the info. It's very helpful.

It's a street car with undercar exhaust and no roll bar. It will not see the street or strip.

It has a BB 390 with about 400 hp, don't know the torque or the rear gear ratio. Looks like I have a bit of research to do before I pick a converter.

[pats401]

I Have An AOD,460,About A3000 Stall,Works Great.Have A Lokar Shifter Rotated To Resemble Original.Am Installing A521 Now,Should Be Fun.

[mr bruce]

FE Big block Ford to C4 Automatic Transmission Bellhousing

[Hotfingrs]

Originally Posted by RACERAL

Thanks Tom... good info. I am planning on my first BB build, the 390 to 445 thing. C6 or C4 it doesn't matter to me. Street use only with maybe 2 or 3 runs down the 1/8 just to see what it will do. I'm hearing about 3600 stall speed for such a ligh weight car. I'm still early in my planning stages, I have had one other roadster, but sold it 3 years ago, and have the itch.

Must be a BB this time... Thanks for the comments guys.

David, I met you one time at VIR , the Club Cranky gang was there.

Al, The higher the stall, the more heat you're going to build. Mostly street driven doesn't need 3600 stall, I'd stay with something in the low 2000's.

[RACERAL]

Hotfingers... man, thats a name from the past.. I met you at London the year you went agricultural racing. Thanks for them info

[Hotfingrs]

Originally Posted by RACERAL

Hotfingers... man, thats a name from the past.. I met you at London the year you went agricultural racing. Thanks for them info

Nice seeing you get back into Cobra's again, I was surprised when you sold yours. The big cornfield race was in 2003. Of course we had about half the power that I have now back then, so now I can go a lot further into the corn.

[RACERAL]

That cracks me up... Wonder if there was any video of that famous run.
I hope to be throwing some junk together soon. Doing my homework now.
That mamma jamma you have had some serious power then, and could walk the talk. You used your HP not just flapped your gums about how "mines bigger then yours"