Thread: 355 sbc with vortec heads

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Originally Posted by Gbilly

Im looking for imput on if in doing this build rite.
It a 4 bolt main bored .30 over, stock 906 vortec heads, I have speed pro hyperkonetics .125 dome top pistons, comp cam adv dur 280 int 280 exh @.50 231-231 valve lift is 480-480 lobe sep is 110.0. It has a stock crank. I was curious about a good intake a carb for this motor. Also curious if someone has built a similar motor and what kind of #s it produced. Thanks.

I don't know if the pop-up would clear the chamber. You might have to do some surgery. Check valve to piston clearance closely. You want minimum 0.080" clearance on the intake and 0.100" clearance on the exhaust valve. 355's make the most power with a 750, but if you aren't trying to make all the power, the motor will operate just fine with a 600/650. I'd use an Edelbrock Performer RPM dual-plane, high-rise intake. It will make more power from idle to 6000 than any other manifold you could bolt on the motor. By the way, your static compression ratio will be right at 11.03:1 and I wouldn't give much for your chances of using pump gas with those iron heads without the whole mess detonating itself to death. I wouldn't build an iron-headed motor any higher than 9.5:1 to 9.7:1 in today's world if I intended to run it on pump gas. If it's a drag motor, then ok, you can use race gas. But then if it were a race motor, you wouldn't be using L31 heads, would you.