TH350 destroyed! Why?

[TheRoaringEagle]

Can a swap from a 10 bolt 2.73 to a 12 bolt posi 3.42 kill a TH350 with a -supposedly- 6 cylinder factory torque converter? I was told that the only remedy for my problem is to get the TH350 rebuilt and install a new converter with lower stall speed. I've also been told I should've gone with a 3.73 gear rather than the 3.42 I got. I'm a little confused but understand that the torque converter must be matched with the rear and the cam.



Any suggestions?

I've got a 400 bored .060 over with a pretty radical cam, 12:1 compression (could that be right? when I found out I thought it was really exteme) and a 750cfm 4 bbl on top of a Holley high rise manifold. The heads are factory camel hump heads I believe and I've been running good on pump gas.

The rear is a Moser 12 w/ Eaton Posi, 3.42

[TheRoaringEagle]

bumpity bump?

[gmachinz]

Wow. I'd say that torque converter was sittin' on the fence to begin with and with the torque of that 400, you prolly blew out a crater right underneath the fence! LOL Anyway, I'd say go with a TCI or B&M Holeshot say....3200-3600 rated stall speed and have fun with it. You said 12:1 on pump gas? You mean 100-octane pump gas or lemonade quality 91 stuff? If you are running with that kind of comp. w/pump gas you'll be needing bearings before much longer. (I've already been there-done that... ) -Jabin

[TheRoaringEagle]

I was really surprised to hear that the 400 sitting in my Camaro had 12 to 1 comp. because it had been running on 91 pump gas for more than 5 years now. Granted the car hasn't been daily driven, but it soon will be. So now I worry.

With the torque converter, I was told to go with a lower stall speed, mid 2ks because of the 3.42s in back and the radical cam in front. I was also told that the 6cyl (supposedly) converter had a higher stall speed which might've been the reason for the 350 to go out! Does that sound right? It all sounds 'ify' to me. Thanks for replying!

[gmachinz]

ehhh....I think you'd be okay with a 2500 rated stall speed-although if you're running 26" tires and with the fairly lightweight of the Camaro-you should be able to get a little more stall speed out of it even with 3.42's (what's your cam specs?). But, I'd say that converter was on the way out anyway. A mildly built 400SB has similar torque as a BB, so I would say the six cylinder converter could not handle it. -Jabin

[Dagger]

Higher than stock stall speeds + weak converter + increased rear gear ratio = higher RPM and more heat. Are you running an external tranny cooler? Heat build-up is poison for transmissions. Just my thoughts.

[TheRoaringEagle]

I have a front mount tranny cooler but it looks pretty old. Now that I think of it, I noticed a low level of tranny fluid on the way down to Long Beach from SF. The tranny was leaking by the time we got there. I just hope the new torque converter will fix the problem. Cam specs are unknown, but "its a really radical cam" is what everyone is telling me. I think I'm going to invest in a B&M Supercooler though. Thanks for the input guys!