Questions head gaskets base gaskets 124

[Raleigh111]

I was sent cometic c10088-036 or H3879SP They say 4.250 .036 on them for twin cooled heads. I am building a 124 .010 over so my bore is 4.135 and i have regular twin cam heads now that are off a 13. They head gaskets measure 4.270 or so? I think i should call back and get the correct ones? Base gasket from s&s are .018 part number 0934-5020 and say 4.125  99 and up on them so I am pretty sure they are fine. Does anyone have the correct part number and a good supplier to get the correct head gaskets? I went to cometic web site and did not find what i was looking for. What i really want is .040 head gaskets for a 124. but i could use .036.

[Don D]

I don't recommend getting and choosing base gaskets ahead of a mockup. Head gaskets are a no go imo. Bore crevice is not a good thing and reduces sealing area around the bolt holes.

[kd]

     (I expect the S&S .018 gaskets are sized to accommodate a common piston in the whole situation as the OEM norm is .020.)

Set it up without base gaskets first and determine what size base gasket you need to get to 0 deck height. Shoot for your best suitable solution to be close.  Now you know what you need for head gaskets to achieve the compression ratio you are looking for while remembering the .030 squish will be your friend to combat pinging and allow for a better tune.

[turboprop]

Jesus. Has anyone EVER seen head gaskets specifically for over bored (ie: +0.010, etc) cylinders? Never.

Good supplier? How about your local indi?

[Ohio HD]

Cometic 4.125" MLS  for TC cylinders have a bore of 4.155", one size fits all.   




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[kd]

The part number doesn't match Ohio's chart.  The head gaskets may be for a 4.250 bore leaving about .020 (.010) rim cavity (if your measurement is correct) but that's a pretty close fit considering dowel hole clearance etc. may allow the gasket to protrude into the combustion chamber.

[Raleigh111]

Cometic 4.125" MLS  for TC cylinders have a bore of 4.155", one size fits all.   




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Thank you. Exactly what I need! C9743.

[Raleigh111]

Jesus. Has anyone EVER seen head gaskets specifically for over bored (ie: +0.010, etc) cylinders? Never.

Good supplier? How about your local indi?

I called a local , told him I was building 124 , 4.125 .010 over  (should of never mentioned .010 over as I know that don't matter) and wanted .040 thick. This is what I got 4.250 .036? Thats why I came back on here to ask or question the size as I was 99% sure they were wrong! Best place to get info is from the knowledgeable people here on this website! Most Indi don't deal with twin cam 124 stuff. At least ones around me. If they do they are building them for paying customers not selling parts for dollars.  Trust me I try to support my locals they just don't support me .

[Don D]

I stock the gaskets. .010 or .020 base sls and .030 4.125 head gaskets which are still right at home at +.010.

[kd]

Raleigh. How do you know you want the .040 gasket if you haven't mocked it up yet?  What thickness of base gasket are you using? Your deck height could be as much as .050 in the hole when assembled.  Like Don said in reply #1, mock it up without the base gaskets and do the math, then order your gaskets to put it where you want it to be.  No ugly and expensive surprises that way.

[Raleigh111]

Raleigh. How do you know you want the .040 gasket if you haven't mocked it up yet?  What thickness of base gasket are you using? Your deck height could be as much as .050 in the hole when assembled.  Like Don said in reply #1, mock it up without the base gaskets and do the math, then order your gaskets to put it where you want it to be.  No ugly and expensive surprises that way.

Thanks and yes agreed. Planning on 0 deck height so having cylinders machined after mock up. They are older S&S cylinders so 5.013 height vs newer twin cam 5.003.  I know forsure I will need to get them cut some so was planning on getting them to match a .018 base with .040 head and zero deck. Maybe I will just wait and mock it up?  Thanks.

[kd]

   I said that because I had head work done and promised the porter that was setting my cc's and cutting my valve reliefs that I would have 0 deck.  When I mocked it up the pistons were .003 out of the hole if using .020 base gaskets.    Machining was not an option and I had to find suitable material to make the base gasket thickness .023.  OCD maybe, but I know my blueprint now and it works as expected.