I was wondering if a 421 or 455 would swap into a third gen firebird. I'd like to run a 4bbl setup with a manual transmission. would it be possible to run a T-56 behind this motor? I have not purchased the firebird yet as i am waiting to research my options. The only reason im looking into this swap is because i can buy the motor for $85 and might be able to find a cheap third gen to throw it at. Your opinions are appreciated in advance

 

if you look around the screen you will see something called a search button. If you use it you will find all the information you need to know. Not only that, this question comes up about twice a week, it may even already be addressed in the current threads.

 

sure you can do it, big question is time and cost. there's a lot you can do cheaper and easier to yield better results.

 

The engine swap is easy and fairly cheap; Indian Adventures has mounts and headers. Id use a TH400 though. The T56 is possible, but expect to spend $3000+ on that swap. Its been done, and any way you do it its not cheap.

 

Alright thanks for the help guys.. im thinking of going with a THM 350 or 400, most likely the 400, and upgrade to a T56 later when the budget allows. I wouldnt mind running a SBC setup with a 700R4 but i have a couple friends that have had nothing but trouble with the tranny, and this 421 is pretty much begging me to find something to put it in... another question the comes up... would a stocker driveshaft work with the swap? or am i going to have to shell out some cash to buy a new one?

 

I don't think your 3rd gen could handle the power of the 421. I've owned one in a 65 2+2 cat. and I constantly broke mounts on the axles, upper A arm bolts, the torque is incredible! HP rated at 376
was under rated because I constatly wupped 400 hp cars with it!
If I were you I would look for a second gen bird that it would fit into nicely and cheap, or something with a full frame! You put it in a 3rd gen. and your going to be throwing money at that car trying to keep the body together!! My Catalina had 3-2's 4sp. close ratio muncie with 3:42:1 posi and it was stock execpt with a
hotter accel coil. When I hit second, the left front wheel lost contact with the pavement. If you really want a big block, go with the stock 455, 350-TH W/street/strip kit, and 3:23's or 3:42's. The 350 can handle the 455 stock and has a lower 1st. gear.

 

The 421 is a great motor, but realistically with any higher output engine in a third gen you're going to need chassis (at least subframe connectors) and drivetrain mods eventually. The Th400 will require a new (or used out of something else, if you don't mind a little scrounging), longer driveshaft, but its also FAR cheaper to build than a Th700R4 or a T56 setup, so you can apply the savings towards that. The Th400 does require more power than the Th350, but it will hold up much better in the long run.

 

I was plaining putting a set of good bolt on subframe connectors on when the origional motor is out of the 3rd gen, and weld them on. then, while im at it, most likely replace the stock springs with a little stiffer ones... im guessing there isnt a company out there that makes big block springs for a third gen, or am i wrong? after i get the motor in i'll drop in a junkyard HEI unit.

 

Somebody like Eaton-Detroit Spring or maybe Landrum Spring (out of Atlanta) could make them for you. I'm using aluminum heads, so weight of the engine shouldn't be significantly different than the original iron small block.