question about 307 heads

[mbc9ieII]

Ok, I currently have 91 350 TBI heads with a mild port and polish job on there right now, will those flow better then the stock 307 heads, i also have a set of 1977 350 heads off of an el camino ss and an extra set of 350 heads lying in the back. but have read alot on here about using 305 heads. I am on a limited budget right now but want the best performance i can get. what heads are better for my set up. i have 307 with .488 lift cam long tube headers 650 holley eldebrock intake and spacer and the current 91 350 TBI ported and polished heads.

let me know what you all think


thanks

[airdale94]

Yes I would say they would flow better. The 77 350 heads would probably flow even better except your going to gain about 10CC's in your combustion chambers. The TBI's are about 64CC's and the 77's are about 76CC's, this will lower your compression ratio. The 305's have a 58CC comb. chamb., which will raise your comp. ratio, but won't flow as good. The lift on your cam just indicates how far the valve opens. The duration ( how long the valve stays open) is what dictates what type of cam you have. Shorter duration builds low RPM torque. While longer dur. builds topend horsepower. Building for topend HP it's best to have large intake runners and more flow. And lowend, torque smaller runners. Just estimating from your big (for a 307) Holley, your spacer, and say a medium range cam, I would say your best with your TBI ported heads. The 307 heads aren't really good for anything except what the factory designed them for - stock economy/power.

I have a 283 with a RV cam, kind of low to mid range performance that had a 750 Quadrajet and 76CC 350 heads and it flowed really great. But I wanted more lowend torque so I put a set of 305 high output heads 54CC and a 500 Holley.

Most street racers want the best of both worlds, for good reasons.