340 with 302 cast head for pickup

txstang84 said

While I'll give you that the engine does sound decent (audio cuts out past about 22 sec), the combo does sound like it would need some tweaking...but I still wouldn't use the 302 heads unless you absolutely needed it to run, like...today or tomorrow.

But, with that same calculator above, I used 4.08 bore, 3.31 bore, stock type felpro 0.053x4.18 gaskets (because if you use anything less, you'll be running a little too close on the piston to head clearance with your slugs out of the deck), 0.010 out of the hole, 6cc valve reliefs, .30" first piston ring, .0025" wall clearance, and 59cc combustion chambers (can be typical for 302 heads)...I still only came up with 10.4:1...totally livable on pump premium if your setup is done correctly.

Click to expand...

I am running the same basic numbers and get 9.88:1 SCR. I used 64cc 302 combustion chamber sizes; I have not ever measured them but all the data I can find is that the 302's typically have 64 cc combustion chambers, stock and without being shaved. Anyone have better info on that? Easy enough for the OP to measure the 302's that he has. That combustion chamber actual size is the key parameter to know here. (And the piston eyebrows' cc's...)

I get 8.11 DCR with this cam; the cam has a lot of duration to lower DCR. Sounds doable to me...... and you'll have a decent quench gap to help. (But I have not thought out the tire size and vehicle weight however.)

As for the question on the original pistons and CR: The 'advertised' 10.5:1 SCR for the original engine was not really 10.5:1. More like 9.5:1 from all I can find. It computes to 9.7:1 with a .022" shim steel head gasket and 73 cc open combustion chambers.