How thick of a head gasket will drop 1/2 point?

[89lxsc]

I have GT40p heads on a stock '89 5.0 block with 0.39" gaskets. I hear the compression with this combo is ~9.5:1. I have a supercharger and would like to be at ~9:1. How do you figure out the head gasket thickness to lower compression that 1/2 point.

Also I have a locwire reciever groove for Felpro 1006 and don't want to go though the trouble of removing it. Any recomendations on thicker gaskets that work well with the groove retained. I was told that copper gaskets work well with the groove. Is there a downside to copper head gaskets?

 

[89lxsc]

GT40p heads are 58-59cc right?

Stock heads are 64-65cc right?

Difference is 6cc.

Felpro 1006 are 8.7cc.

So, if the above is correct then a 14.7cc gasket would be good.

Anyone know if SCE Titans are good?
They make them in a couple sizes that are close.

15.3cc -
http://store.summitracing.com/partdetail.asp?part=SCE-T36067&autoview=sku

Says it needs oring. Is that the same as the lock wire?

13.7cc -
http://store.summitracing.com/partdetail.asp?part=SCE-T36156&autoview=sku

 

[89lxsc]

After talking to Cometic and SCE I am convinced that the reciever groove must be taken off. Even thicker gasket now!!!

I am not sure which gaskets I like better the MLS or the self-energizing copper. I am leaning towards the MLS because of evenness of torque distribution. I am a little concerned about the <50ra surface finish requirements though.

Can someone confirm the cc numbers for the GT40p heads and the stock mustang heads?

Thanks.

 

[89lxsc]

Here's a pic of the reciever grooves. 4.125"ID, 0.010"Deep, 0.085"Wide.

 

[smr]

I would runa good MLs gasket (cometic) and see about gaining your compression with some minor head work...Your heads dont appear to have any bowl work done to them. You could gain across the board by getting them cleaned and opened up little and not los the quench by installing a taller/thicker head gasket.