So in my Firebird I have a slightly modifed original 350. Heads are stock, engine is 30 over (now a 360) cam is XE256H. Has headers and a two barrel.
I also picked up a 557 block, machined for 9 to 1 cr. 10 over, new rotating assy when rebuilt, heads are ported and polished 6X 8 and are milled. Cam is a summit 2801.
I bought the 400 carb to pan with headers and all accessories for 550 bucks. I know i can turn this around for an easy profit.
Now here is the dilema, if i put a Qjet on the 350, how different will the two motors be? I tried deskstop dyno, And the 350 made slightly more HP on a wider rpm range. ???Torque was slightly lower. i have a hard time believing that, and want your opinions.
Thanks!

P.s. Also posted on Firebird Nation

Anybody?

Are you sure that 400 motor has 9:1 CR with 6X-8 heads?? The 6X-8 heads have a pretty big combustion chamber and even with flat top pistons and the milling, I'd be shocked if you are truly at 9:1.

I've always thought that the Pontiac 350 was a very underrated engine. Years ago, I had a 71 Lemans Sport convertible with a 350, 4bbl, and a set of 3:23 gears. That car ran strong. The 350 had great street manners and pulled hard through the gears. I beat quite a few 5.0 Mustangs in some stoplight racing. Of course the hot rodder in me wanted more and the stock 350 was replaced with a mild 455 but that's a story for another day.

The Summit 2801 is very similar to the factory 068 grind cam which is a great street cam. I'd say that 400 would run strong in your car. If you're looking for a little more oompf then drop it in and hold onto the 350.

Yes, I'm pretty sure. The seller Is an honest guy. He spent $3500 on the engine 10 years ago. The block has been zero decked and the heads milled. I agree with you on the 350, it is very powerful and has gobs of torque. Definitely will not sell it.

Over on the PY site most people frown on using the 557 block because they are a thin casting in the mains and considered very week.

As stated above the 6X-4 350 (and 77-79 T/A 6.6), 93cc, 2.11/1.66"
6X-8 400, 101cc, 2.11/1.66"

If the 6X-8 heads were milled .050 to get 91cc and 0 deck would be about 8.8 compression with a 041 gasket. With a .027 head gasket you would get 9.02 compression.

Seems the numbers speak for themselves.