pontiac firebird and 400 small block

Home  \  Classic Cars  \  pontiac firebird and 400 small block

iv got a 400 small block and im wonderin if it is possible to put that into my v6 1989 pontiac firebird and also wonderin what kind of work i would need to do

posted by  firebird2850

How the hell do you come up with a 400 small block

posted by  99integra

got it of a chevy
y u surprised

posted by  firebird2850

Because you can't have a 400 small block, it would have to be considered a big block then

posted by  99integra

iv got it in my garage right now

posted by  firebird2850

I believe it was actually considered a long block.

posted by  SlipKnoT

every where else it says its a small block 400

posted by  firebird2850

Chevy made a 400 small block it is based on the 350 with a larger bore and a longer stroke. if you put a 400 crank into a 350 block you can make 383.

It would not be an easy job. but it is do-able. I'm sure i will miss something but here what I would say would have to be changed:


exhaust
tie up un-needed wires
motor mounts (unsure)
fan shroud
radiator (might need a larger one)
fuel lines


I'm sure there is more, but thats all I can think of at the moment.

posted by  corbett_auto

if the motor mounts need changed, that could affect the placement of the trans mount and crossmember? and then you might have to shorten or lengthen the driveshaft. i would say definately heavier front coil springs though.

posted by  adamc44

Well you gotta remember its only an '89 Firebird, so therefore it would still need emissions would it not? I'm guessing the engine is probably older then the car and may not pass emissions.

posted by  car_crazy89

you've spent too much time on older cars, corbett... :wink2:


exhaust (just need y-pipe & possibly converter, depending on y-pipe)
tie up un-needed wires
motor mounts (parts store, 305 or 350 car)
fan shroud (not required, electric fan...)
radiator (parts store, 305 or 350 car--check pn's, v8 & v6 might be the same rad)
fuel lines (depends on induction system, you may have to reroute to the pass. side if you're going w/ a mech. fuel pump)
transmission (you can use almost anything that will bolt up to a sbc--th2004r. th350, th400, th700r4, it's just a matter of what other folks decide your opinion is)

bunch of other miscellaneous crap, depends on whether you go carb, tbi, tpi, etc...

you'll probably want to swap the trans crossmember for an earlier one, b/c yours has the crappy rubber isolator setup (earlier cars are one solid piece)

good luck! :thumbs: :thumbs:

ps: for the record, a 383 is a 350, .060 over, w/ a 400 crank...

posted by  dodger65

Well damn, I just learned something :doh:

posted by  99integra

yea and actualy they even have 454 small blocks. world products blocks are cool like that. you can get 427 and 454s from there 350 blocks

posted by  72firebird

I have made the 305 to 400 swap and oh man was there more to it than i thought. Does anybody know if there is a smaller slave cylinder replacement for a 1991 manual tranny?

posted by  1991Firebird400

Interesting. Swapping a 400 SBC for the 305 is no big deal at all. What was "more to it than you thought", why do you think you need a different slave cylinder and why is this post in someone else's thread?

posted by  vwhobo

well, a bigger engine leaves less room for the slave cylinder since they put those extra cubic inches in he bellhousing area where you can't see them so it looks like a 305... :screwy: jeez, hobo, dont'cha know anything? that's like the oldest hot rodders' trick in the book.... next to lightweight blinker fluid...:wink2: :laughing:

posted by  dodger65

1991 with a five speed i had to find a custom flywheel because the original flywheel had the bolt pattern for a one piece rear main seal engine and my small block is a 1973 chev 400 with a 2 piece seal and the difference is the counter wieght on the crank and the bolt patterns on the flywheel, and on top of that i had to find a custom starter that would fit in the bellhousing but with the staggered bolt pattern instead of the new style straight across pattern and as most of you know the header issue is always a problem but believe it or not the cheapest crappiest flowtech headers solved the problem for now, but that bring's me to the issue of my slave cylinder no longer clearing, they are a little too close to the header for comfort, so i need to find a smaller size cylinder and thats about it.:sleep:

posted by  1991Firebird400

Your Message