Sorry for taking so long. He just got back to me today. He has been out with the flu. His price for cometic head gaskets is $70 per side, but his warehouse only stocks the 0.040 gasket. It may be more to have one ordered, but I may be able to have it sent right to your house if I place an order. Let me know if you want me to look into it more.


FWIW - did you ever just consider milling your heads down 0.030-0.050? You wouldn't hurt them at all, you could dial in your cc size, and it's not all that expensive (my machine shop charges $80 for 0.020, and they'll do the next 0.020 for less). You should be able to do some light bowl blending yourself, better protect yourself from detonation issues, and have a more dialed in motor. Just my $0.02...

The price sounds good. When it gets time to install the heads I'll let you know. As to the machining, I think I am going to have them milled a bit.. I need to CC them and see where I'm at.

Thanks for looking into this for me.

A 454Mag has a comp ratio of 8.75:1 and so do the 400, 420, 425. They are all 454's and use the same pistons, head gaskets and heads.

I would just mill the heads .020....in fact that is exactly what I did do with the 454mag I had in my 24 OL.

if he mills the heads,should intake also be milled??

not for only .020''

For .020, the intake will fit fine and in most cases .030 is fine.

Sounds good, thanks guys!

I believe roughly for every .010 milled you reduce chamber size by 2c. If you milled them .020, you should gain about .25 compression.

Griff, what kind of performance gains did you get out of this?

I did a lot of other stuff at the same time also. I did a complete top end with cam, carb, roller rockers, and Imco exhaust. The engine was very similar to Merc 420 when I was done.
I picked up 400-500rpms and about 5-6mph at WOT. Probably gained 60-70hp or so. I figured the milling was maybe good for 10hp.

I gave my specs to somebody else and he dynoed his engine at 425hp at 5000rpms. The only difference was he also changed intakes. I was spinning mine at 5400rpms.