Modifying a '73 400 motor for a '68 Firebird convertible with Muncie M21 4-spd and 3.55 posi. Using CompCams #51-223-4 cam with lift of .477 IN and .480 EX.; also using stock pistons, stock connecting rods, stock push rods and stock crank. Want to shave 4X heads down from stock 98cc's by say .060 to get to about 86-88cc's and a c.r. of 8.6-8.73 to 1.
1. Can this be done in this configuration without the valves hitting the top of the pistons?
2. What is the max. amount that can be shaved in this configuration and what compression ratio results?
3. Ideally would like to get to a compression ratio of 9.0-9.5; so what amount of shaving of these heads would SAFELY get me there?

Thanks in advance for expertise, advise and leads. ... Ken

For your application, 4X have press in studs, not too reliable for a mild build up. As far as milling heads, you will have to have the intake sides milled after .025 on the deck side. I would recommend 6X-4 or 5C heads..

No Banshee our 4X heads have screw-in studs. Our milling answers again are?????