Picking the right head gaskets.

[TexasRoadRunner68]

For a 4.375 bore motor, what size gasket would you go with? Is 4.380 good? I have heard you want it slightly bigger than the bore.

Also, are mopar performance ones any good? They have a set at .025 which would bump up my CR a bit. With a 0.039 head gasket, I should get 10.4:1. I would assume the .019 difference would make it 11:1 or so? The cam manufacturer recommended a minimum of 10.5:1.

 

[pnora]

What heads? Myself I would not use these. I would use a composite.

 

[69Bee]

Also, unless your pistons are at least 0.010" in the hole, your going to have a problem with piston to head clearance.

 

[RemCharger]

With .000 deck pistons I'd go with a .040 cometic. People will speak of concerns about the deck finish, I myself have never seen issue with many builds
That will give you great quench.

 

[69Bee]

Surface finish does need to be smooth for MLS. They routinely recommend single digit to teens for the RA. If the surface finish is too rough, hot sealing can be okay, but when the engine is cold and contracts, it can leak. Every iron block and head I surface gets a smooth surface finish using a CBN (Cubic Boron Nitrate) cutter insert, and aluminum is cut with a PCD (Polycrystalline Diamond) insert.

 

[TexasRoadRunner68]

What heads? Myself I would not use these. I would use a composite.

With .000 deck pistons I'd go with a .040 cometic. People will speak of concerns about the deck finish, I myself have never seen issue with many builds
That will give you great quench.

How much over the 4.375 bore would you go? 4.380 or possibly a bit bigger? It seems some advise 0.01 over bore diameter.

 

[69Bee]

I would not get that close because your gasket will hang over into the bore chamfer area. OE head gaskets are usually 0.090" or more allowing up to a 0.060" overbore. I would try to keep it at a 0.030" larger than the current bore, or close to it. Had a customer that we got close to the bore, but he didn't like the poor OE chamfers from the factory; they can be really horrible at times. Well, he got out his die grinder, and screwed it up by hogging out the chamfers so that the gaskets hung into the bore, and then proceeded to blame it on me!!!

 

[TexasRoadRunner68]

I would not get that close because your gasket will hang over into the bore chamfer area. OE head gaskets are usually 0.090" or more allowing up to a 0.060" overbore. I would try to keep it at a 0.030" larger than the current bore, or close to it. Had a customer that we got close to the bore, but he didn't like the poor OE chamfers from the factory; they can be really horrible at times. Well, he got out his die grinder, and screwed it up by hogging out the chamfers so that the gaskets hung into the bore, and then proceeded to blame it on me!!!

Something like this?

 

[RemCharger]

Bingo

 

[69Bee]

Yes, 4.410" @ 0.040" Thk. If no one has any in stock, call Cometic at 800-752-9850

 

[not so famous bob]

Yes, 4.410" @ 0.040" Thk. If no one has any in stock, call Cometic at 800-752-9850

I used 4.380 cometic .039 gaskets , ( bought theme on eBay for $80 back then) in my current 505'' wedge , 4.350 bore , gaskets came out perfect after compressed , dead even with the cyls. that was about 12-13ish yrs. ago ... torqued and re torqued 4 times during the build , but waited till the last time to go full torque ...