318 build.

hwy2 said

I have put on speedmaster 170 heads 65cc, cool gap manifold pertronix 3 distributor. Thumper can .514 lift its .040 over. Question is I have a 550 low end holly, or a 750 single pump with race bowls. I fell I relly need a 650. Any help would be great I will put up a small 6sec video to so you can hear. Please any thoughts will be great.

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My thoughts…. What exact cam is it? We are missing duration @050 numbers, compression ratio, headers or exhaust manifolds.

Given what you have said, the 750 will work fine. The 550 is a bit small and will tip the secondary side more often. While I’d agree a 650 is probably more spot on, the 750 is what you have that will work best. I wouldn’t bother purchasing a new 650 carb myself.