I have a 4.375 bore BBC w/ BB 2X Heads. I had used the Felpro 1047's that have a 4.540 bore. This gasket fits the intake valve unshrounding area perfect and the exhaust side is real close, but is as much as .135" wider then the chamber itself on the spark plug side. Not to mention it is much wider than the bore.

Is there anything to gain by going to a head gasket that fits the bore and head better ? I assume the copper gaskets ( which I prefer not to run ) could be profiled around the valve areas to help with the unshrouding, can the MLS / Cometics ?

Any suggestions would be appreciated

Nobody has anything to offer on this topic ?

I have a 4.375 bore BBC w/ BB 2X Heads. I had used the Felpro 1047's that have a 4.540 bore. This gasket fits the intake valve unshrounding area perfect and the exhaust side is real close, but is as much as .135" wider then the chamber itself on the spark plug side. Not to mention it is much wider than the bore.

Is there anything to gain by going to a head gasket that fits the bore and head better ? I assume the copper gaskets ( which I prefer not to run ) could be profiled around the valve areas to help with the unshrouding, can the MLS / Cometics ?

Any suggestions would be appreciated

Stay with the 1047's or the 1017-1's. The mismatch at the bore is not going to hurt a thing in my opinion.
The small bore is hurting your flow way more than any perceived problem with the gasket not being close to it,, again in my opinion.
Lay the block back at the intake valve especially & you will pick up a bunch of flow with the small bore.
You would need to use the big bore Cometic's as well or the sealing ring will hang into the head chamber which is not the best way to seal the engine.

Stay with the 1047's or the 1017-1's. The mismatch at the bore is not going to hurt a thing in my opinion.
The small bore is hurting your flow way more than any perceived problem with the gasket not being close to it,, again in my opinion.
Lay the block back at the intake valve especially & you will pick up a bunch of flow with the small bore.
You would need to use the big bore Cometic's as well or the sealing ring will hang into the head chamber which is not the best way to seal the engine.


Thanks ! Thats what I was planning on doing, just wanted to make sure since I have never used the cometics.

Get yourself some of the new Cometic head gaskets. Just dyno'd 632 with 16.2 C.R. without the inner head studs in the block. (World Products doesn't cast them in the lifter area) We were waitin' for the gaskets to lay out, but no problem. We're gettin' away from dead soft copper and stainless "O" ring wire, which we've used for many years.

Get yourself some of the new Cometic head gaskets. Just dyno'd 632 with 16.2 C.R. without the inner head studs in the block. (World Products doesn't cast them in the lifter area) We were waitin' for the gaskets to lay out, but no problem. We're gettin' away from dead soft copper and stainless "O" ring wire, which we've used for many years.
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I agree completely, haven't "O" ringed a block in about 2 years now & all the "O" ringing we did was always with a receiver groove.
The MLS Cometic's are about as good as it gets for gaskets :thumbsup:
Hell, you can even use them over of you have a mind to in a pinch.
We used the same set on an engine on the dyno about 4 times while playin around with some stuff a while back with no issues.
Not recommending this as the best plan but it shows how good they are.

But, for almost all of the applications on this board with a few exceptions, the FelPro performance gaskets are more than adequate & about half the price

I'll agree here, Cometics are the way to go, but you have to pay a lot more attention to block and head surface finish. Things need to be smooth, REAL smooth, or else you'll have a leaker. Only way to check is to get a profilometer out and verify the surface finish on the head and block-- it needs to be 50RA or better, better being preferred. Too rough and they won't seal. Unlike standard gaskets with a lot of compressible sealing material the Cometics rely on a very thin (on the order of .0015") layer of Viton to do the sealing. It is not tolerant to pits, deep mill marks, etc.

I've got a set of Cometics hanging on the wall at home I couldn't use last time I had my engine apart. While my heads were perfect, a couple areas on my block weren't up to snuff as far as surface finish requirements. Didn't want to chance a leak, so I just used Fel Pro's again.

If everything is smooth enough to use the Cometics (or other MLS gaskets) go for it. An added benefit with them being all metal is they really help heat transfer between the head and the block.

Troy