How do you size your TQ converter on your heavy car?

[Bad Byrd]

I dont have a ton of experience sizing TQ converters on these heavier cars.............not a lot of experience with these heavier old school cars. Generally as a whole I dyno the motor check the TQ curve and size the gear ratio and TQ converter based off that information.

I am not going to go to that expense on this car, the car isnt built to this level so its a bit of a guessing game for me. Based off of Mr Brown guess of me having 475HP and a 3900 lb car with 3.50--1 gear ratio what would you run? Right now I am thinking a 2200 Stall  converter.

Motor is a 445 Ci Stroker
4.160 Bore
4.125 Stroke
Roller Cam

The cam was custom ground based off of 3.50-1 and a 2400 stall. However knowing this thing is HEAVY, I am concerned of overheating the trans fluid, even though I have a redundant trans fluid cooling system...............Radiator and independent trans cooler with fan.

[jayb]

I always used to worry about overheating the trans fluid with a loose converter too.  Over the last 10 years I've gradually stepped up stall speeds on various cars while monitoring transmission fluid temperature, and have been really surprised to find that until you are running the car down the drag strip, the fluid doesn't seem to overheat at all with a very loose converter.  Currently I'm running a 5600 stall converter in my Mach 1, which is 3600 pounds with me in it.  The transmission fluid temperature never goes over 190 degrees, even on a hot day while driving down the freeway.  I have an Earl's transmission fluid cooler on the car, but its not a big one, probably 4" X 10" or so.  Temperature reading is taken from the pan.

At the track at the end of a run I'll see the temperature rise 30 degrees or so without use of the transbrake.  It will get VERY hot if you apply the trans brake and hold the car on the brake for any more than a second or so at the starting line, so I try to avoid using the transbrake.

Most of this may not be relevant to your situation, but the point is that you shouldn't worry about the converter selection affecting your transmission fluid temperature.  I'd heard that for years from various sources, but based on my experience it has turned out to be an old wives tale.  The converter selection for your vehicle will be more about how much "slushiness" you can deal with just driving the car around.  2200 RPM is pretty close to stock for stall speed; I think I'd go at least 3000 with your combination, and probably even 3500.

[afret]

I think Jay is right.  You always hear about keeping the stall below highway cruise RPM or the trans will overheat.  I've always run loose converters and never had a problem with the trans fluid getting hot.  I had a 4500 converter when I used to drive to the track with a medium size B+M cooler and the temp wouldn't go much above 170* on the highway in the desert summer heat.  I only had 3.91 gears with a 28" tall tire going about 55 down the road so the revs weren't high.  The car is a '69 Mustang and isn't very light.
Have gone to a loose 8" converter now with the same cooler.  Haven't driven it much but the trans temp has been fine going down the road.

Going loose (up to a point) will help your car launch if you take it to the track and let the car idle better in gear if you have a bigger cam.  Jay's recommendations sounds good to me.

[Bad Byrd]

Not to be argumentative Mr Brown but when I went to a 3200 stall on the wifes 32 roadster I saw an increase of well over 30 degree's trans temp on the freeway. So I added a fan to the trans cooler and I got 20 back! Now that is a 383 Stroker SBC with a TH400, but that car doesnt weigh 2200 lbs.

So I just assumed that with a big ole Tuna Boat I would see even a greater increase in heat.............maybe the C6 is a better trans then the TH400 in this scenario but I wouldnt think so!

[e philpott]

camshafts and converter's go together along with intended application , all other factors are minor ..... converter's job is to get the engine into it's operable rpm torque range and cam plus cubes is the main determining factor ....... I totally agree with Jay , I ran a 5000 stall converter on street for thirteen years with no problems or over heating in a C6 ..... best way to size a converter is to call the converter manufactorer  and give him your application (street , street and strip or strip) engine size , cam , gear and weight .... one thing to consider is converter diameter , a small 9 inch converter has way less fluid capacity than a 11 inch converter , my 5000 stall converter was made with a 9 inch cover to help retain some fluid capacity .... even with a deep pan it only holds around 7 quarts total capacity , so based on total fluid capacity the 7 quarts has to run a little hotter than a 12 quart system just from lack of fluid capacity

[Bad Byrd]

Mr e philpott

I agree and I have indeed called 3 different MFG and here is what I found so funny and it has happened to me before.....................they all had different opinions and recommended different stalls. I had as low as 2200 all the way up to 2800.

The thing they all had in common was the elevated temps with higher stalls. Now I am not disagreeing with anyone and thats why I am here to ask the question................because I cant seem to get a like for like answer from the MFG and to be honest you guys you arent trying to sell me anything and they are.

Besides here is real world and their info is more what I like to classify is a lab world.

[e philpott]

I did a edit while you made your last post , sorry about that

[blykins]

It would be hard for any company to make a converter recommendation without all engine specs, including dyno numbers.  Torque will change the stall speed, so without the exact numbers, the best they can do is give you a ballpark, unless they're extremely familiar with your exact combination.

[e philpott]

I still think the temp difference is minor , your not going to burn up your trans cruising around or having fun ..... the worse thing you can do to over heat a tranny is to set there and power brake it for 5 minutes straight , temps will raise no doubt ..... My friend and crew chief for Jerry Daily's hemi super stocker (back in the 90's)  told me that sitting on the line at 6000 rpm on the trans brake is what made their temps go up if there was a staging war  , they went up enough that they installed a bigger trans cooler , you probably won't have that problem though

[Bad Byrd]

It would be hard for any company to make a converter recommendation without all engine specs, including dyno numbers.  Torque will change the stall speed, so without the exact numbers, the best they can do is give you a ballpark, unless they're extremely familiar with your exact combination.

I agree which is why on all my past builds I have spent the $ to have the engine dyno'd then ordered the TQ converter. Being it isnt a drag car I will probably just run a 2200 or 2400 and call it good. No real point in having a loose converter if I am not going to use it all that often I guess.

I did give them the engine specs just not they Dyno numbers which i dont have..............so I am not casting blame anywhere just thought I would get some opinions here to sway my decision one way or another.

[jayb]

Not to be argumentative Mr Brown but when I went to a 3200 stall on the wifes 32 roadster I saw an increase of well over 30 degree's trans temp on the freeway. So I added a fan to the trans cooler and I got 20 back! Now that is a 383 Stroker SBC with a TH400, but that car doesnt weigh 2200 lbs.

So I just assumed that with a big ole Tuna Boat I would see even a greater increase in heat.............maybe the C6 is a better trans then the TH400 in this scenario but I wouldnt think so!

That's an interesting result, and contrary to what I have seen with my own cars.  What were the temps you were seeing?  The fact that you added a fan and got the temperature back down on the freeway may indicate that the cooler on your wife's car wasn't getting good airflow.  I guess I should say that I always put my coolers in front of the radiator, not behind, and I always use a "good" cooler like an Earl's, not the round tube type.

[cjshaker]

I don't know where the cooler was placed on the '32 Roadster, but they ain't exactly the best cars for airflow
Even if it was put in front of the radiator, that area is pretty small and confined. That may have contributed to the temp rise even with a cooler.

[Bad Byrd]

Not to be argumentative Mr Brown but when I went to a 3200 stall on the wifes 32 roadster I saw an increase of well over 30 degree's trans temp on the freeway. So I added a fan to the trans cooler and I got 20 back! Now that is a 383 Stroker SBC with a TH400, but that car doesnt weigh 2200 lbs.

So I just assumed that with a big ole Tuna Boat I would see even a greater increase in heat.............maybe the C6 is a better trans then the TH400 in this scenario but I wouldnt think so!

That's an interesting result, and contrary to what I have seen with my own cars.  What were the temps you were seeing?  The fact that you added a fan and got the temperature back down on the freeway may indicate that the cooler on your wife's car wasn't getting good airflow.  I guess I should say that I always put my coolers in front of the radiator, not behind, and I always use a "good" cooler like an Earl's, not the round tube type.

Because the Grille on the 32 is a Stainless bar type the cooler couldnt go in front of the Radiator too Ugly, and behind would have been in the engine compartment and that wouldnt have looked good either. So the B&M plate and frame trans cooler was mounted in the space age frame under the car. The temps I saw where in the 195 to 200 degree mark after the stall converter was installed.

The only thing that changed was the stall converter was added, never saw trans fluid temps that high until then. There was a nice little scoop that directed air over the cooler from under the car. Once I installed the 8" Spal fan the temps dropped.