C6 torque convert - which one shouyld I use?

[Tom Wells]

I have a 12" TCI Saturday Nite Special that I'm planning to use, mostly for street with the occasional driving school.

It is behind Leroy, a 521", tame big block.

Will this torque converter be OK, or should I look at something else? I want to do some highway cruising too.

Tom

[Jack21]

Tom,

The components sound mismatched to me. I wouldn't consider myself any expert on this, but the guys at Performance Automatics in Gaithersburg MD are. Had I gone the C-4 route on my 351W, I would have bought it here.

They can install it for you too.

[cobrashoch]

Tom- The 12 inch converter sounds about right to me. Most 12 inchers stall around 2500 on big block engines. If a 12 inch converter stalls any higher they tend to slip above 5500 rpms, and this will build up heat and cause converter/tranny life to shorten. To stall any higher and not slip on the big end you must go to a smaller converter. Heat generated by slippage is the bad guy here. Ideally you want the the converters stall to be less than the rpm range you cruise around at. That way you keep things nice and cool. I also feel that a tranny that has a "loose" converter should have a tranny cooler to. In fact, I feel it's almost mandantory for street performance cars anyway. As for the C-6,
I would use it if for no other reason than you have it allready. Just make sure it'a a good un' though. Using a C-4 for performance could make a good subject for another thread, as there is some advantages AND disadvantages to going this way.
cobrashock

[Tom Wells]

Jack21,

Thanks for the local lead - I have their number and will call them tomorrow.

cobrashock,

Thanks for the confirmation of my objectives with this - heat generation and slip I don't need! You have articulated my aims quite well. My cruise speed on the highway will be well below 2500 with the 2.88 axle. I'll keep those parameters in mind when I make my call tomorrow.

I already have a "built" C6 and the Saturday Nite Special ready to install, so we'll see if they convert () me to something else!

Tom

[427sharpe]

No reason to 'convert' to a C4 unless you are racing. C6 was a big block trans, handles mo' power, but the C4 is much lighter. Your combo should be great for what you have done.

[cobrashoch]

Tom- Number one mistake guys make with converters. High stalls at cruising range causing slip. Changing rear end rations is the answer for the pro street boys. Don't forget to price a cooler to.
cobrashock

[Tom Wells]

cobrashock,

I have a special aluminum radiator for this car, 1/2" thicker than the usual E-M big block radiator, with an auto trans cooler located in the passenger side header tank. I guess if I need to, I could put another oil/air cooler in series with that one.

What do you think?

Tom

[cobrashoch]

Radiator should work fine. No need to add a extra cooler on for a street car . Many aluminum aftermarket radiators don't have the cores set up for automatics. Have you bought a converter yet? I have a personal "thing" for Turbo Action converters. Costs more but there is a REAL differance there. Also a dropped tranny pan is a inexpensive add on that helps for your tranny too.
cobrashoch

[Tom Wells]

Jack21,

Had a long chat with Performance Automatic's Harvey Baker and we concluded that a basically stock torque converter was the best one for my needs. Low stall speed is his advice - 2000 rpm sounded OK. Thanks for the source for the affirmation! Looks like the Saturday Nite Special I already have is the ideal one to begin with.

cobrashoch,

As to cooling, I have a nice old Art Carr finned aluminum pan which increases the trans's capacity by a quart or two while adding a bit of cooling. I probably should contact the radiator mfr about how good the internal heat exchanger is - if it isn't enough, I'll go with a big oil/air cooler.

Tom

[Jack21]

Tom,

Kinda figured that would be PA's take on this. A heavy duty, but otherwise stock converter would be what you'd want to use.

Still not sure you're going to be overly happy with 12" SNS with this combo. Behind a tweaked 351 Cleveland, this would be ideal for the street.

You're putting a 521ci, tame (650 fptq @ 2500RPM), big block in a 2400# car and driving it on the street. You've got a bottom end - mid range torque monster that's going to be a handfull just keeping the wheels from breaking loose. A higher than stock stall speed converter will only make this worse. A heavy duty, but stock, or even an RV converter, and low rear gears, 2.74 - 2.88 or so, should get better traction, less wheelspin, and use the engines' torque where it's making torque. Since the car is so light, and you're not winding the motor, a bone stock OEM converter for a Galaxie or Lincoln would work and be inexpensive. Let the PA guys rework the valve body in your C6 for Street Rod use. A street rod valve body is typically used in big block-light car applications. The trans changes gears faster, but the engagement is softer so it doesn't chirp the tires and snap your neck under light load.

And, since the trans isn't slipping much, you don't have to cool the trans fluid much.

[Jay]

Tom,

I am also about to get my converter for my set up. I am only running a 514 with a C-6. I called TCI tech line (662-224-8972)and they gave me their converter choice. They are going to need your cam specs, tire size and rear end ratio. They gave me a stall a little over stock approx. 100o over. It is called a break away part # 441101. They said I would not be able to use the next larger converter unless my rear end was 3.5:1 or deeper.

Jay

[Tom Wells]

Hello Jay,

That's interesting. I gave TCI all those specs for my car, and they came back with part number 441001, which is the same converter but with the 460 pilot size (1.375"). It sounds like you have the FE size pilot (1.850"). Make sure which size you have before you place your order!

Being hard-headed (I like to think of it as "independent thinking"), I'm sticking with the Saturday Night Special. My reasoning is that the engine is large but quite tame (hydraulic roller cam, vacuum secondary carb, etc.) and I'll be doing some significant highway miles, so high stall is not a desirable thing. If I was drag racing only, or not running much on the street I might want more stall. Or if I was using the solid roller cam that came with the crate motor which had very aggressive bracket racing cam timing and lift specs.

So my stall with the SNS will be a little bit more than a stock unit, but less than the eleven inch Break-A-Way unit. If, after I try it out this turns into a "learning experience", the price of education will be cost of the higher stall unit + installation. It's a bet I'm willing to make.

TO ALL: what kind of cooling are you doing?

Regards,

Tom

[cobrashoch]

Jay- "ONLY" a 514 ? oh well. My take, I don't like the impeller/stater setup that TCI uses for street cars. Can't argue that they are the best selling converters though. TCIs are set up for lightness as apposed to size/weight copnsiderations that other converter manufactures will be more than glad to explain to you. For example my converter is heavy, we are talking boat anchor here. But It will handle much more heat and slipping for much longer than a TCI. With differences out there like this, the most important thing to do is use the manufacturers suggestions that you bought your converter from. As for the cooler, I am a bit unique here I should think. I use the oil cooler in front of my car as a trans fluid cooler aft of my radiator. I don't use a oil cooler on my car, at least the way it's intended anyway. I have had a few folks look at that thing and say, " that looks like a transmission cooler". DAAAAA! Oh, I almost forgot, pay the extra bucks for a good flexplate and bolts. Can't overstate the safety involved here. As for the lack of a oil cooler on my car, that is a subject for another thread. Suffice to say I don't think they are even a good idea for most street cars.
cobrashoch

spellin' so bad I had to edit this darn thing.

[jdean]

Hi Tom,

It is good to get some validation of similar set-ups.

For the car I am building, I also have a 460, relatively mild ( Torker II, vacuum secondaries, medium cam, tweaked heads, 9.4 CR) Torque is a bit north of 500 lbs. I do have the B&M shift kit in the C6 I am planning to use, also with a SNS converter. Rear end ratio is 3.08. Will be for 98% road use.

Jack 21 - when I read your advice to Tom, I am thinking I might have goofed already on one decision.........When I put the shift kit in the C6, I used the "firmer" shift option (you know, where you drill the one hole in the plate bigger and use the extra ball bearing) - Do you think this might leave it shifting too harsh for my set-up?

[toolguy]

Anybody use a B&M 2500 stall convertor? I have a FFR with a 351C and I am putting in an AOD with it. They are the only company I can find that makes a 2500 rpm stall and still locks up in 4th gear. It has a .70 overdrive in the AOD with a 4.10 rear looks like it will give a highway ratio of 2.87. But I dont know anyone who has this setup. B&M convertors any good?

[cobrashoch]

Toolguy - B&M gooooooood. They don't have as many models as TCI. They are my second choice though. Make sure to use their trick shift tranny fluid to. Not sure but I think they are owned by Holley.
cobrashoch