I have a pair of 416 305 heads that I plan to get machined to take bigger intake valves and have them fully ported. I also, want to get them milled to 54cc but I do not know if that will be over doing it. I heard that when you mill heads the ports that match up on the intake manifold sometimes don't line up correctly. What would be an okay amount to ge them milled. I have a stock 350 engine with the flat pistons with relief valves or something and I want to bring the compression up to 10.5 - 10.7. I heard that your car gets louder and you make more power with higher compression.

 

The chambers are 55cc to start so getting what you want is simple. Once they cut for bigger valves the chamber will be a bit bigger. Tell the machinist your plans and he can mill accordingly, if he doesn't know then he isn't worth paying. Getting what you want will not require milling the intake as well.

The general "rule" for SBC heads is mill .01 per CC you want to drop. I'm no machinist though, someone correct me if I'm wrong here.

More compression gives more power through-out the entire power band. A lot of people credit it with adding "throttle response", which is probably more due to the added low end power you get raising it.

All that said though you probably don't need to mill them anymore then just to clean up the surface, with these heads on a flat-top 350 lack of compression is the least of your worries.

 

I thought that the chambers were 58cc? Well, I could be wrong but just say that they were, would milling them to 54cc be too much? Also, does anyone know what the compression would be on a 350 flat top piston bored .040 over with the 54cc 416 heads be?

 

What size valve reliefs on the pistons?

I measured the chambers my self, that isn't me repeating something I read or heard. You'll find other people reporting the same too. I have also read 58cc for them so I know where your coming from.

54cc with 6cc valve reliefs would be way to high for a daily driver if you used the right gasket for .040 quench and standard deck height on the block.

If they finish at 58cc after the cut for bigger valves you should use 12cc dished pistons, standard deck height, felpro 1094 head gasket. That would give you perfect 0.04 quench and 10.3cr.

this is the calc I'm using; http://kb-silvolite.com/calc.php?action=comp