Hey guys, would appreciate some help here I am just getting more and more lost as I read more about them.

So.. I've got a reasonably high overlap cam (XE 274h) with 10.5:1 compression in a 350 which should make a theoretical 450hp 440ft/lbs at the crank. Car is also a '75 with a Th400 and weighs about 3400lbs empty. I'm not totally sure what gears I have either, I think it's between 3:20 and 3:55.

I'm getting a new converter because the one in the car is 1800 according to my trans builder and I've got issues with it riding up to 15mph at idle and terrible off-idle performance. Any idea what I should do?

Comp says I need a 2400 effective stall, but I can't figure what stated stall will result in 2400 with my vehicle. I also don't understand whether I should go 10" or 12" for the converter. This one from B&M has caught my eye, 10" 2400 stall. Also, what do people mean when they say "tight" and "loose" stall and how do I apply that to my options?

This is so complicated

 

You need a higher stall speed (looser) converter to handle the big cam. Unfortunately it will also be looser at high speed leading to more heat and wear.

GM made a switch pitch TH400 trans with a variable lock up torque converter. I have one in my Buick GS, stall speed is around 3200 but then I can lock it up with a switch for top end.

 

What size TC are you going to run? I have a 9.5" YANK SS3200 in my 82 right now and LOVE it, but I am going to a SS3600 soon. My 3200 drives just like a normal stock TC until you hit the loud peddle and then hang on. Those BIG diameter TCs are crap and have used them. 9.5" is the way to go IMO.

 

Mines 2800 Stahl FTI 9 " it doesn't slip nearly as much at part throttle but it's an animal when I nail it. The small diameter is much lighter and the engine revs up quicker which makes driving in traffic snappier. FTI makes a good unit. I used to know Jim Beatty at ATI very well about 30 years ago and he always made great stuff for me, now Jim is gone and don't think I ever met the kid.I live 60 miles from FTI now and they are great to work with. I have a Racer Brown SSH-14 Cam on a 110 centerline so it's pretty tough too.

 

Get with a converter builder so they can set you up with what you need. They will want to know everything you have posted about your car, cam specs, gearing, etc. They will build it to your car. I went with Edge converters, give Andre a call and he will build one to work specifically for your car. https://www.edgeracingconverters.com/

 

I don’t think 2400 will make you happy. Go at least 3000 stall. I had a 2600 and switched to a 3000 with great results. Just don’t go cheap, you’ll get what you pay for.

 

My concern with that is having a converter with a higher stall than my cruise speed. I cruise at about 2600 at 65mph

 

I'm thinking you need to check that rear end ratio. If your running that low of RPM at 65. I really doubt your rear gear is as low as you think. Jack her up in the rear and count the drive shaft revolutions.

 

2650 rpm would be correct for a stock size rear tire and 3.23 gears.
At 65mph.

That's not a lot of gear for a cam like that. You are going to need a convertor. Get a good one. Let the convertor builder spec the unit. They'll know.

 

This should not be an issue, especially with a good converter. I have a 3000 stall speed converter in mine and it will cruise at 1,500 or 2,000 rpms continuously without a problem.

 

Make sure it is a lock-up convertor too
BKbroiler what brand and model is your convertor?

 

agree here with BK.

OP, Just be sure to have an additional cooler to keep trans temps manageable. A good converter will not slip excessively even below stall, and very little when cruising below stall.

your rear is not a 3.55. Mine is and 65 is about 3000 rpm.

 

My converter is from Transmission Specialties in Aston, PA. I don't know if they assign model #s to them, but it is 10 inch dia, 3,000 stall. They are fairly expensive but I originally had a B&M bargain converter. That didn't last 20 runs on the track before it suffered some internal failure. The Trans Specialties unit has about 230 runs on it, in the 12.2 to 12.4 range, on drag radials, with no problems.