Thread: Building a new motor

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Which 305 heads?

Originally Posted by sefrayser

Which 305 heads?

See, this is what is so exasperating about trying to help someone. If you had been reading what I wrote, you would already know that there are two part numbers of 305 heads that I might use on a 283 if I had to make a choice. See the bottom of my post #2 on this thread.

The other thing about the 283 heads is that there are no drilled and tapped accessory holes in the end of the heads, so everything that you use as an accessory will have to be anchored off the intake manifold and the exhaust manifolds.

And for the rest of you knuckleheads out there, Edebrock makes heads with 2.02" or larger intake valves and 1.60" or larger exhaust valves, so there is interference with the smaller bore size of the 283 block. That's why I recommended the Trick Flow 305 heads as well as the production 305 heads, because there is no valve interference.

sefrayser, if you're at zero deck, you will not be able to use 0.021" gaskets. The pistons will crash into the underside of the heads when the motor gets up to operating temperature. Use Fel-Pro 1003 (0.041").

Next thing is, do not try to operate this motor at 9.9:1 with iron heads. You're inviting detonation. You might get away with it using premium pump gas and you might not.

Last thing, I have no idea where you came up with 9.9:1 SCR. A 283 with +0.030" overbore, stock stroke, zero deck, Fel-Pro 1003 gasket and heads with 58cc chambers will have an SCR of 9.05:1. Cut the heads to 54cc's and you will have a 9.5:1 motor, like I've been telling you all along. Or leave it 9.05:1, I don't care.

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