[Will]

There are three different versions of the #46 head.

The first was used in '69 on 400 & 428 engines. Not sure of the chamber volume on this version. It was a small-valve, pressed stud, low compression (for the time) head. Chamber volume is probably in the 80-90 CC range.

The second was used in '73 on 2bbl 350 applications. This also is a small valve, pressed stud head. Information suggests chamber volume is around 87CC.

The third version was used on the '74 GTO, which had a 350 with a 4bbl. This version has screw-in studs, but still small valves (1.96"/1.66"). The compression was pretty low on this engine, so the chambers are also probably in the high 80cc range.

All of these heads will work fine on a 400, and if the chambers are in the mid 80 CC area, say 86cc, then you'd end up with close to 9.2:1 compression if the block is bored .030" and cut for zero deck height.

However, having pressed studs limits the cam lift and duration you can run, and having the small valves limits engine breathing and RPM range. You could have larger valves installed and have the pressed studs pulled and replaced with screw-in studs, but that of course all costs money. It might be cheaper to start with a set of big valve heads that have screw-in studs already. Research your options before spending your money.


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'72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car!
'73 Firebird 400/4-speed Black on Black, mix & match.