My new 400 block is currently in the machine shop with the rebuild kit, heads, intake manifold, carb, ect.. all on order. With the vortech heads and new agressive comp cam and other goodies im told about 350 - 370 HP at the crank. My budget doesn't allow for an immediate transmission swap, and my car is equipped with the stock 5 speed (1987). Ive know the reason that you couldn't get the 5 speed with the 350 in '87 was due to failure with the increased torque of the 350 TPI... But im also told that many fellow camaro buiders, and others, use the IROC 5 speed in combination with engines pushing more hp and torque than the stock 350 made in '87... can anyone shed some more light on this please... anyone have a first hand experience with the transmisson doing either great or horrible...??

I do plan on being reasonable with the pedal. The car is going to be a daily driver with no plans for racing or track time..

 

You have an '87, then?

You understand you'll need a different flywheel. Not only is the 400 2-piece rear main seal, but it's externally balanced as well. You could have the crank internally balanced, but that ain't cheap. And, you can't us a 168-tooth 400 flywheel in a T5 bellhousing (won't fit).

You could get an external balance 153-tooth 2-piece rear main seal flywheel. That won't be cheap, either.

I wouldn't consider a 350-370 HP 400 all that aggressive. What Comp cam are we talking about?

I have never bought into the story that the 350 had too much torque for a T5. My belief has always been that they didn't want f-bodies outrunning Vettes.

(BTW, I believe you mean "Vortec" heads, as used on '96-'99 Chevrolet/GMC light truck engines.)

 

Yes it is an '87 and I know that my stock 305 flywheel won't work; however, i didn't know that a 400 sbc flywheel won't work with the T5 bellhousing... i will have to talk to my machine shop about that, thats no good. The comp cam is part number 12-250-3 with .507 in. and .510 ex. valve lift with 1.5 rockers. Thank you for the heads up.

 

I spoke with the machnie shop manager and he says that i need to have a 10.5 inch flywheel out of an 85 or older.... i believe the flywheel out of a chevy monza will work great, and somewhat reassured me that with my limited slip diff and stock size radials that the tires should break loose long before my old T5 starts to break apart. Also you are correct about the clylinder heads. The motor should be in by the end of march if I don't run in to too many troubles.

 

Is he going to internally balance the crank, or are you getting an external balance flywheel?

An internally balanced flywheel (the application is '83-'85 f-body V8) could also be drilled to make it external balance.

 

he is going to externally balance the flywheel.

 

Cool. Sounds like he knows what he's doing.

Have you picked a flywheel yet?

 

I just spoke to the shop manager today and he has a bunch of friends who race circle track so he's going to try and grab me a second hand one they've taken off a monza, but if not ill just order a new one. Rebuild kit came in today but im off for 3 days vacation so ill just wait until monday when he says the block should be complete or very close to it.

 

Your T5 will probably hold up fine. I've got a quite a few runs on mine at the track with drag radials at it hasn't broke. It's gone 12.8s.

But that's not to say yours isn't going to break *shrug*

It will be fine if you aren't beating the **** out of it constantly.

 

I ran high 12's with a 400 in a 90 firebird and shattered the T5 going from 2nd to 3rd. I admit, I did beat the crap out of it.

I didn't trust it so I upgraded this time. Lots of guys here run stock T5 trannys but they are not hard on them. Do you know the history of yours? It may be about to go anyway...

If you break it or don't want to risk it, look for a T56. If I had to do it a gain, I would have gone this route.