cometic head gasket bore size

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chrgdrt

chrgdrt

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doing a refresh on my 416 after my 2nd set or 1008's gave up. had the heads (edlebrock) and block resurfaced. so I'm going with cometics this time my question is the felpros have a bore size of 4.125 the cometic's come in various bore sizes. I'm at .030 os which is 4.070. the cometics come in 4.080 and 4.125 bore size so the question is will the 4.080's work or should I go with the 4.125's.
Thanks,
Gary
 
chrgdrt said:
doing a refresh on my 416 after my 2nd set or 1008's gave up. had the heads (edlebrock) and block resurfaced. so I'm going with cometics this time my question is the felpros have a bore size of 4.125 the cometic's come in various bore sizes. I'm at .030 os which is 4.070. the cometics come in 4.080 and 4.125 bore size so the question is will the 4.080's work or should I go with the 4.125's.
Thanks,
Gary
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4.100 -4.125 sounds right to me.
I dont want a ton of crevis area but I dont want the gasket sintering away either like I have seen with those gaskets when they are too close to the bore size.
 
Can't go by bore size, have to consider the chamfer at the top of the bore.
 
That's pretty much the way I was thinking, just wanted to hear what others thought, maybe i was missing something.
I'll measure the chamfer and see what that comes out to.
 
The registration of each bore to the head gasket holes will not be be perfect. So I'd be surely going to the 4.125" holes. Made a similar choice on the .020" over 340 here for that reason.
 
Measure your bore and head chamber size and contact Cometic. They'll know what you need.
 
chrgdrt said:
That's way too easy when I can get all kinds of advice and recommendations here!
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that head gasket will flatten out and spread a little too. I run a 4.380 bore gasket in my 4.350 bore 505 , and it smashes out to the edge of the cyl . almost perfect .
 
Studs? Did it push the gasket into the valley? I had issues with the 1008’s when I didn’t re-torque. I changed to torquing them down and let them sit over night. Then I would go back and back them off a 1/4 turn and re-torque. They would all turn more. Never had an issue after that. Went with cometics and studs when I bumped the compression to 12.2 to 1
 
furrystump said:
Studs? Did it push the gasket into the valley? I had issues with the 1008’s when I didn’t re-torque. I changed to torquing them down and let them sit over night. Then I would go back and back them off a 1/4 turn and re-torque. They would all turn more. Never had an issue after that. Went with cometics and studs when I bumped the compression to 12.2 to 1
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ARP bolts, no didn't push out the valley. first time after removing headers for recoating and reinstalling #5 filled with coolant and wouldn't turn over.
2nd time notice exhaust escaping at the deck at 4 & 6. both of these occurred after about 4 or 5 years of useage. decided it's time for refresh and make some changes.
 
Might be over kill for you, but studs are better even if just for the fact they are 3/4” nuts instead of the short 9/16” head of the arp bolts which can be PITA. Be careful when installing the cometics. My 360 block and x heads pinched the rivet on the gasket in the middle of the head. I just drilled out that rivet and no issues. Just pay close attention.
 
It may have, but I REALLY didn’t want to hear my pretty expensively ported head go Crack! It is a pretty thick rivet. Also there are two other rivets

23151298-027D-44F9-A795-921776E2CE4B.jpeg
 
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It wouldn’t sit down on the dowel pins, rocked on the rivet.

7F0CB34D-108A-4A39-8B88-C07D68FA2BCE.jpeg
 
I contacted Cometic and got a reply back the next day, they had what my engine builder wanted a 3.670 for a 3.665 bore 273.

Alan
 
It’s not like it’s a “we hate cast iron head” thing either.

BE469CD1-DAEB-4144-A270-9A9AE543545C.jpeg
 
The rivets were not an issue (273 w/OE heads), they stick out beyond the block and the head presses them over a little.
Image2.jpg



Alan
 
furrystump said:
Might be over kill for you, but studs are better even if just for the fact they are 3/4” nuts instead of the short 9/16” head of the arp bolts which can be PITA. Be careful when installing the cometics. My 360 block and x heads pinched the rivet on the gasket in the middle of the head. I just drilled out that rivet and no issues. Just pay close attention.
Click to expand...
thanks for the heads-up (pun intended), I'l keep that in mind when i get to that point. been contemplating studs but I'm only @ 10.5:1 I shouldn't be having these issues.
 
You’re right, at that compression you shouldn’t have issues running bolts, but it’s talking to you. It might not be a perfectly flat deck or the head could be a little off or the block threads could be pulled up a little. Small blocks really should have the fifth head bolt, so it is one area I go for overkill.
 
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