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I need an odd thickness head gasket to get my quench thickness in the ballpark. Best thickness would be .057 compressed. I can get copper exact thickness. MLS come in .060 and .050 compressed. Heads and deck have a plain old machine shop finish.
Which ones do you guys suggest, as I can't get composition gaskets other than .039 or so compressed.
If you use cometic gaskets, it is important that the head and block finish be correct.
Recommended 50RA or smoother. If there is any printing in the metal they will probably leak.
Cometic will make you anything you want as an MLS. Many choices available already. Ck Ferrea also..I used some of their composition gaskets on mine when N/A for years with no issues.
I've got Fel Pro MLS on my car now with the turbos. No issues.
Thanks for the replies. That was my understanding about the need for a particular surface finish to use MLS gaskets
The thickness needed is frim measurements. The block has been decked and align bored so much that the pistons are .017 above the deck at TDC. I'm running. 039 composition gaskets with .025 copper shims. They work, but they're not the best setup and that puts the quench thickness at .047, also not the best.
Overall what I'm running is ok. I'm looking for a way to trim it up a bit. If there isn't, I'll live with the motor as it is.
Cometic will make you anything you want as an MLS. Many choices available already. Ck Ferrea also..I used some of their composition gaskets on mine when N/A for years with no issues.
I've got Fel Pro MLS on my car now with the turbos. No issues.
JIM
Looks like Ferrea doesn't do gaskets anymore......shame. Went to the site......
Thanks for the replies. That was my understanding about the need for a particular surface finish to use MLS gaskets
The thickness needed is frim measurements. The block has been decked and align bored so much that the pistons are .017 above the deck at TDC. I'm running. 039 composition gaskets with .025 copper shims. They work, but they're not the best setup and that puts the quench thickness at .047, also not the best.
Overall what I'm running is ok. I'm looking for a way to trim it up a bit. If there isn't, I'll live with the motor as it is.
My engine has the pistons .009" out of the deck. The Ferrea's I mentioned listed as .040" but actually compressed to .037.....which put me at .028" total clearance. Worked well with some slight visible "rub" marks on the pistons and heads. Never an issue with ring lands, bearings etc. I was pushing right to the limit and of course spinning a lot of RPM.
Currently I'm using .041" Fel Pro MLS #1077 gaskets that give me .032" total clearance. This also gives a little "rubbing"...but understand these are 2618 material pistons with more wall clearance and "rock" than the previous 4032 material pistons I used when N/A.
It looks like the Fel Pro .051 gasket gets the thickness where it needs to be. What's the feeling on using a 4.5" bore gasket on 4.3" cylinders? That's a .1" annulus that's. 051 thick. It seems that would ba a good place for pinging to start? What do you think?
Just FYI….so am using a Mr. Gasket 1134G on this 385 build….(.040)…..I bought a pair of 5746 Mahle gaskets but with the gasket bore at 4.100 and a finish bore of 4.040 the chamfer put on the bore at the top while not excessive…was putting the fire ring of this gasket too far toward the edge for my liking….
This 1134G is perfect at 4.125 bore…..and at .028 crushed….gives me exactly what I need on this one with .010 in the hole pistons….
The material is like the old Corteco Sticky Rubberized coating….and I can tell you these will seal off the border if you need them to….great gasket….used this style many times.
BTW…this is my High Average Torque 385….smallish Dart heads (180) with a nice hand blend….a nice hyd roller cam 230’s at .050 and 10.4 to 1 compression…EPS with divider milled and a 750hp….
should make 440ft/lbs. torque from 2500-5500….440 horsepower @ 5600rpm…..490-500 peak torque….
Should twist some tires….
Jebby
Last edited by Jebbysan; Feb 18, 2023 at 03:34 PM.
So, just out of curiosity, what would you say the max amount of gasket bore diameter to cylinder bore is acceptable?
Well….you wouldn’t want it extreme….like a 4.640 fire ring on a 4.310 bore big block….but most quick chamfers done with the abrasive cone will open up to another .080 total (.040 radially) leveling the edge of the fire ring to hangover the bore…..
IMHO….on a .040 thick gasket or thinner….up to .100 (.050 radially) or a little more isn’t going to cause issues….thousands run the 4.166 Fel Pro 1003 on a 4.030 355/383….
I have had Cometic MLS on my 496 big block for over 20k miles with no issues. They were custom made by Cometic for the engine builder. Cometic adjusts the coolant hole sizes to help balance the coolant flow. That makes them side specific. No issues for me.
Which head gaskets, solid copper or MLS on BBC?
