In my quest for a replacement engine for my '91 Firebird, I've come across a new twist. Originally, I had planned on replacing the stock 305 TBI with a carburated 350. I think that I've changed my mind. Today, I came across a Chevy 400 for $1,500 that has peaked my interest. It was in a street/strip S-10 pickup truck that ran low 12's ("spinning the tires half-way down the track").

What I know so far:
Chevy SB 400 bored 0.040 over
less than 10K miles
Edelbrock Performer RPM Heads/Intake
Comp Cams 286H
Holley 750 carb

To me, this sounds like a good deal. Only problem is, this engine would undoubtably break my stock T-5 tranny and stock rearend in no time. So I'm hoping someone has done a similar swap and could offer me some advice.

I'd like the car to remain a stick-shift, if possible. I read a little about the T-56 trans swap from the '93-'97 f-body cars (in the tech articles section). This swap would be great for my Bird, but I fear that I won't be able to locate one for a reasonable price. As an alternate, I was thinking along the lines of the old faithful Muncie M-22 "rock crusher" transmission. I'm sure that I can come across one for far less than the T-56, but I don't know how difficult it would be to perform that swap. Would I need a new drive shaft? Could I keep my stock bell housing? I'm assuming that the stock rearend can be gutted and improved with stonger parts. Any suggestions?

I have until this Saturday to make a decision. Thanks to all that reply.

 

Well my 400 runs mid to low 11's on the original rear. No,I didn't reuse the T5. I used to have a M22 Muncie 4-spd in it but now have a TH350 in it with a 8" ATI Treemaster converter.

 

i've been running the stock rear for 3 years behind a th350.the rear has got a powertrax set in it. i'm using a 2400 holeshot.i am afraid of the rear tho- take it easy on the launches , 2.1 60' times. i would be interested in hearing about a 4 speed swap. what kind of clutch setup were you using?

 

Why the switch? If you dont mind me asking...and wich do you prefer? I ask because the 400ci is my next upgrade.

 

Well let me first say that I really miss the four speed. What I don't miss is swapping clutches, u-joints, etc on a regular basis. Tried several different clutches but the biggest problem was the bellcrank ratio. The factory ratio is all wrong if you want to power shift through the gears. By that time I'd had enough of pulling it apart and had the TH350 I've had forever in the cellar gone through. It has all the good stuff in it and hasn't given me a lick of trouble. The converter I have now is the second one only because I didn't like the first one. I only did the swap mostly because I no longer street drive it and I find the auto to be much more consistant and it is much easier on parts.