Shims To Bump Compression

[earlbrown]

Shipping goes up everytime gas goes up.  For some reason it forgets to go back down between spikes.


Shipping to Canadia wasn't that bad in the old days. I recall frozen hosers talking about the high price of freight, but when I'd mail over the border it was only a dollar or two more.


Now it's a pain in the ass. I shipped over the border a few times in the last year and I had to itemize every single part, what it was worth and what each part weighed.

Then, when I got done the label was too big for the box and I'm pretty sure it said all of it had to be on the same face.

What's bad is I can mail a small flat rate box with 70lbs in it to Hawaii or Puerto Rico for 6 bucks.  If it goes over the border it's now 20US and can only weigh 4 pounds.

What's the part number on the Fel-Pro's you're looking at?  The only name brand shim gaskets I know of here are the Cometics at 100 clams a piece.

[Steve Wood]

Earl needs to develop a pop off valve in the head of each cylinder to release any pressure spike from detonation then close again when it goes away...save a lot of work.

right now, it seems the rjr shim is the only game for me.  too bad, he does not offer a thinner one

[earlbrown]

How thick is the RJC gasket?   Cometics can go down as far as .027"


It just sucks that I'm committed to running them after decking my block and machining my intake before I developed my pistons.

[Scoobum]

RJC's are .035 compressed

[Steve Wood]

I thought the Cometic was for a Stage block? With a larger bore.

No, I am wrong.  It's a 3.860 bore and will fit both standard/Stage   http://www.cometic.com/i-24769025-buick-192-231-252ci-v6-027-mls-cylinder-head-gasket-3-86-gasket-bore-stock-stage-i-ii-heads-each.html

[Scoobum]

True or false? I read the Cometics require a mirror finish to seal properly.

[Steve Wood]

Only if you believe them.  But, if you look at all the stuff that users use...maybe not...

Cometics are made to go on without any sealer.  they have a coating on them that should seal on a smooth surface.  To obtain such a surface, the heads and block need to be cut with a grinder not a mill which leaves tiny grooves in the surface.  The link I provide above says viton

so users, spray them with copper coat, or such.  Some go to the hassle of separating the pieces and spraying each piece so coolant cannot seep between the layers.

Billy told me to try spraying top and bottom with Hylomar.

[Steve Wood]

Cometics should be good when using aluminum heads which move around a little on cast iron blocks due to temperature growth differential

[Scoobum]

Norbs ran Cometics on the S1 block and TA heads he had. I crawled underneath with the engine warmed up and could see oil seeping between the block and heads. I know the block was milled...and the heads were as he got them from Nick Micale. I somehow think I recall Norbs said he sprayed the Cometics with copper seal...but I may be mistaken on that one.

[Steve Wood]

They seem to be holding on my Mopar but I have heard lots of complaints on Buicks....

[Steve Wood]

TECHNICAL SUPPORT
CAN MLS HEAD GASKETS BE USED WITH MOTORS SETUP WITH O-RINGS OR RECEIVER GROOVES AROUND THE CYLINDER BORES?
No. MLS head gaskets require smooth, flat and true head and deck surfaces to seal. Most of the time with o-ring setups the wire and groove fall where our gasket’s combustion seal is located; therefore, the wire will hold the gasket and not allow proper compression while the receiver grooves allow combustion gases to escape.

WHAT SURFACE FINISH IS REQUIRED TO US AN MLS HEAD GASKET?
A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design.

WHAT HEAD BOLT/STUD TORQUE DO YOU RECOMMEND WHEN USING AN MLS GASKET?
When using MLS head gaskets always refer to the manufacturer of the fastener to determine accurate torque values. Appropriate torque is critical when installing new gaskets of any kind.

WHY DOES COMETIC RECOMMEND MLS GASKETS TO BE INSTALLED DRY?
Cometic Multi-Layer Steel (MLS) head gaskets go on dry because they are coated with a sealant. Each MLS head gasket is coated with a .001" thick Viton rubber that is bonded to the outer stainless steel layers. Adding an additional sealer can hinder the performance of an MLS head gasket.

[motorhead]

The steel shim head gaskets used in LS engines are very forgiving when it comes to surface finish and straightness.

[Scoobum]

TECHNICAL SUPPORT
CAN MLS HEAD GASKETS BE USED WITH MOTORS SETUP WITH O-RINGS OR RECEIVER GROOVES AROUND THE CYLINDER BORES?
No. MLS head gaskets require smooth, flat and true head and deck surfaces to seal. Most of the time with o-ring setups the wire and groove fall where our gasket’s combustion seal is located; therefore, the wire will hold the gasket and not allow proper compression while the receiver grooves allow combustion gases to escape.

WHAT SURFACE FINISH IS REQUIRED TO US AN MLS HEAD GASKET?
A surface finish of 50 RA (roughness average) or finer, is recommended for a proper gasket seal. Anything rougher may conflict with the gasket design.

WHAT HEAD BOLT/STUD TORQUE DO YOU RECOMMEND WHEN USING AN MLS GASKET?
When using MLS head gaskets always refer to the manufacturer of the fastener to determine accurate torque values. Appropriate torque is critical when installing new gaskets of any kind.

WHY DOES COMETIC RECOMMEND MLS GASKETS TO BE INSTALLED DRY?
Cometic Multi-Layer Steel (MLS) head gaskets go on dry because they are coated with a sealant. Each MLS head gasket is coated with a .001" thick Viton rubber that is bonded to the outer stainless steel layers. Adding an additional sealer can hinder the performance of an MLS head gasket.

There ya' go.

[Pyro6]

For what it's worth. I run a RJC gasket, I didn't have a problem til I screwed up and overboosted at Summit a couple years ago. it was good for the weekend, we went into the car show, came back to the track. Next day we got rained out and headed home. We raced a couple times at Maple Grove and it spit compression at #4. Pulled the heads, discovered seepage at #4. Head gasket was still good, the heads passed at the machine shop, the deck was good too. I think what happened is what Steve said earlier, the head lifted. Additionally, momentarily broke the 3M seal and it took a few runs to show up. If I just ran it on the street it probably would have been OK or at least took a lot longer to show up.
In my opinion, a MLS gasket is used for aluminum heads to a cast block OR a condition where the head "walks" excessively.

[Steve Wood]

I have seen several shims get lifted and heard the motor boat sound when it happened.  Retorquing seems to get you back in business most times.

BTW, what size of socket does it take on headbolts?  5/8"? or is 11/16?