So I want to take my 305 out of my firebird. But I dont know which type of block I should get. I am stuck between a 350 or 327. I was also looking at the lt 1 engines and I dont unerstand wat makes them better. I was also told that if I am doing a full rebuild that it doesnt matter where the block came from. So I could just rebuild a 350 from a van and still get the same performance as if I rebuilt a 350 from a camaro. thanks for the help greatly appreicated.

 

-350 is the most common, and easiest to find.
-327 has a different crank, and either a different bore or stroke or both (dont remember exactly what)
-lt1 is a second gen small block. idk if id concider it "better" but that depends on what you value to be "better"

 

350 and 327 both use (or at least, can use) the same block. They are both 4" bore. A 67-back 327 block can't readily interchange with a 350 however, because the crank journals are smaller.

You don't want a 327 anyway. It's the same bore as a 350, in some years made from the same block casting in fact, except with a stroke that's ¼" shorter. OTOH, as you're well aware, people make 350s into 383s to get MORE POWER; and they do that by .... {drum roll please} putting ¼" LONGER stroke into the same block. Which should tell you, taking a 4" block and using the short stroke, is a step backwards. There is NO advantage to it. Don't even bother considering it.

What you were told is exactly right: power output doesn't depend on the source of the block. All 350 blocks are exactly equal, when it comes to power output. 350 CID makes 350 CID of power. The way you get more or less power, is by the choice of pistons and heads (compression and flow), cam (RPM range), and other parts that SUPPORT the block. The block is just kinda there.

So yeah, get one from a van or an Impala or a Vette or a .... whatever. Just make sure it's a small block Chevy one, as there were also Buick, Olds, and Pontiac 350s, of which ABSOLUTELY NOTHING WHATSOEVER will interchange with your car, except maybe the spark plugs and a couple of bolts.

I'd suggest getting a newer one, so you can get the provisions for a factory roller cam. That's MUCH cheeeeeper than the roller system we all used to use before the factory got hipped up to rollers somehow, and the Engineering department let their summer intern did that .... thing .... they did, as his junior project. Or however it came to be. Regardless of how weird it is, it's AHELLUVLOT cheeeper to go fast with that, than an older block. As well as, the quality control in the 70s SUCKED, and got MUCH better after about the mid 80s.

 

350 is 4" bore and 3.48 stroke
327 is a 4" bore and 3.25 stroke
305 is 3.735 (IIRC) and a 3.48 stroke

All the parts are interchangeable in all the blocks except pistons. Also, I've "heard" that if you use a 305 crank on a 350, it needs to be rebalanced due to the weight differences between a 305 and 350 piston. I could be wrong, somebody more knowledgeable I'm sure will chime in.

LT1 is a 'reverse flow' 350. In a nutshell, it has a 'better' cooling system that runs in the opposite direction of a Gen1 SBC- heads down versus block up. You can't bolt the heads and intake from a Gen1 onto an LT1 (GenII). Bottom end and cam are interchangeable. Different block, heads, and intake.