Cometic Multilayer HG's - Oh No, Not another thread

[Jerryl]

So, from what I gather, there are a few techniques listed, provided;
A-All surfaces are better than 50Ra, and flat.
B-Surface areas are clean, dry and oil free
C-Retorque after one day or as long as possible
D-Seal the threads of the bolts, obviously

The techniques for Cometic ML HG installtion are listed as;
1-Install dry and "as is" (Per Cometics website )
2-Remove rivets, coat all layers with copper spray, assemble in order, add GM seal tablets.
3-Remove rivets, coat only inside layer on both sides with copper spray, assemble in order, add GM seal tablets.
4-Remove rivets, coat all layers with GE1200, assemble in order, add GM seal tablets.
5-Remove rivets, coat inside layer on both sides with GE1200, assemble in order, add GM seal tablets.
6-Remove rivets, coat all layers with thin coating of silcone sealant arond the water passages and section to the lifter valley, assemble in order, add GM seal tablets.
7-Remove rivets, coat inside layer on both sides with thin coating of silcone sealant around the water passages and section to the lifter valley, assemble in order, add GM seal tablets.
8-Remove rivets, add a very thin coating of silcone around the water passages only and section to the lifter valley, add GM seal tablets.
9-Remove rivets, add a very thin coating of silcone around the water passages on all layers, and only and section to the lifter valley, add GM seal tablets.
10-Remove rivets, coat all layers with HYLOMAR, assemble in order, add GM seal tablets.
11-Remove rivets, coat only inside layer with HYLOMAR, assemble in order, add GM seal tablets.

So, which one worked for you to get a leak free installation?

Anyone try Permatex adhesive sealant between the layers?
Description of PERMATEX 80065
HIGH TACK SPRAY-A-GASKET Sealant
All-purpose sealant that sets fast to seal and hold the heaviest of gaskets in place.
Remains effective under extreme temperatures of -65F to 450F. Resists gasoline, oil, kerosene, propane and butane. Level 1
Suggested Applications:
Seals all felt, cork, metal, paper, rubber and asbestos gaskets

 

[Grumpy]

A-All surfaces are better than 50Ra, and flat.

we used our first set on a flat clean surface that was not 50RA (hey it was a "crunch time moment"

B-Surface areas are clean, dry and oil free

doesn't that go without saying ???

D-Seal the threads of the bolts, obviously

same as above.


1-Install dry and "as is" (Per Cometics website )

have used them right out of the package with no problems


Have also used "HYLOMAR" on previous used Cometics on the top and bottom of the gasket. NO we didn't take the rivets out.. we also add GM seal tablets.


I think a lot of people go overboard "thinking"

 

[Jerryl]

A-All surfaces are better than 50Ra, and flat.

we used our first set on a flat clean surface that was not 50RA (hey it was a "crunch time moment"

B-Surface areas are clean, dry and oil free

doesn't that go without saying ???

D-Seal the threads of the bolts, obviously

same as above.


1-Install dry and "as is" (Per Cometics website )

have used them right out of the package with no problems


Have also used "HYLOMAR" on previous used Cometics on the top and bottom of the gasket. NO we didn't take the rivets out.. we also add GM seal tablets.


I think a lot of people go overboard "thinking"

Thanks Dan.
If anyone would know how to do this, it would be you. (No pun intended)

So, let me confirm what I think to understand; "Dry, as is, out of the box"?

 

[yullose]

I ground off the rivets and used a thin film of black RTV silicone around the water passages on all layers, including the deck and heads. No sealing tabs in the cooling system at all, but I DO only run a 7lb radiator cap.

A retorque is also a must. I had a couple loose ones after a few heat cycles.

 

[Grumpy]

Thanks Dan.
If anyone would know how to do this, it would be you. (No pun intended)

So, let me confirm what I think to understand; "Dry, as is, out of the box"?

When we did our "crunch get it done now" we just used them out of the package.. After that we do coat the top and bottom when we reused them. I now would coat the new ones to. Lots of guys have had problems with sealing so I figured just spray em before we put em on. we don't retorque them after they are running in the car.. To lazy :biggrin: so far its been fine . I think we are one of the most driven GNs out there . 8000+ miles this year

 

[Scott Atk]

I'm a HYLOMAR guy... although it's getting harder and harder to find. You want the aerosol not tube.

 

[Grumpy]

I'm a HYLOMAR guy... although it's getting harder and harder to find. You want the aerosol not tube.

X2

 

[Jerryl]

Just called and according to Permatex Tech Support:
"We do no recommend HYLOMAR for any HG applications. We recommend copper spray, 2 coats on both sides."

Permatex is just a dsitributor of HYLOMAR.
That may explain it. Interesting . .

 

[ryan319]

i installed my dry with ARP bolts to 70ish ft/lbs, a few GM tabs and they stopped the very minimal dripping in a few hundred miles. no retorque needed.

i'd follow the instuctions per cometic. grinding off rivets and coating them in copper spray is sillyness. if the deck and heads are straight you should have no issues with them sealing.

 

[bison]

Here is my experiences. Ive used nothing and had them not leak on freshly machined surfaces. Last time i used copper spray on the gaskets and in between and they leaked. IMO Hylomar would be a better option since it is non drying and has worked on everything else ive used it on. I re-torqued 2x before i got no movement

 

[Otto J]

I spray both outersides of the gasket with copper spray and install and torque immediatley.
Let sit over night and loosen each bolt and retorque them one at a time.
Never had a leak

 

[Super6]

I spray both outersides of the gasket with copper spray and install and torque immediatley.
Let sit over night and loosen each bolt and retorque them one at a time.
Never had a leak

this is what i do..except i use a heat gun..let it sit over night and retorque..no leaks here also.....Bob

 

[ta88gta]

A-resurfaced the heads
B-Surface areas are clean, dry and oil free
C-Retorque after one day or as long as possible
D-Seal the threads of the bolts, obviously

Did all of the above but also pulled the rivets and coated all the surfaces with permatex super 3000 form a gasket. retorqued with heat guns same day and again next day. No gm tabs used and so far no leaks.

 

[Cme2fly]

i installed my dry with ARP bolts to 70ish ft/lbs, a few GM tabs and they stopped the very minimal dripping in a few hundred miles. no retorque needed.

i'd follow the instuctions per cometic. grinding off rivets and coating them in copper spray is sillyness. if the deck and heads are straight you should have no issues with them sealing.

+1
Torque 70lbs with Molly or 85lbs with sae 30. i used pipe thread sealant on the bolts or studs with great results. No tabs here..As for removing rivets and copper coat thats is just nonsense.. No re-torque 3 years later..

 

[gnxtc2]

- Removed the rivets.
- Found garbage between layers
- Coated layers with copper spray
- Cleaned deck and heads with laquer thinner
- Torque cycled studs (5 times)

Billy T.
gnxtc2@aol.com

 

[UR50SLO]

I decided to do the Drill rivits.. degrease and clean each one.
Copper spray on each side of each layer of gasket.
Assemble back in order on block.. install head.

Torque with heat gun.. sit over night.. torque again.

Since then not torqed yet. Been alright but I'm not pushing mine hard.
~Scott

 

[Pablo]

factory finish on block
Heads resurfaced for non mls gaskets but pretty smooth (dont know the ra)
removed rivets
liberally sprayed each layer with copper coat
ensured head and block surfaces were very clean
30w oil on studs torqued to 85 ft lbs

no leaks

Don't know how much it helped but I am very anal about how I torque fasteners. A torque wrench is only as good as its user. Smooth, slow movement, force applied at 90 deg from the wrench and at the right location, measuring sliding friction vs static friction, etc etc. Of course I ran the nuts up and down the studs several times to burnish the threads too.

 

[turbobitt]

I spray both outersides of the gasket with copper spray and install and torque immediatley.
Let sit over night and loosen each bolt and retorque them one at a time.
Never had a leak

Believe it or not, Some big engine companies like Cat Diesel recomend lossening the bolts and going over the torque sequence over again right after the initial torque. Seems to work very well. I have also done this on Copper/O-ring applications with success.
Allan G.

 

[Jerryl]

Just wondering is anyone here ever used the Felpro PermaTorque head gaskets? (PN: HS9441PT)
Just wondering since these are supposed to be a lot user friendlier.

 

[JayC]

Id use GE 4000. You should be able to get a tube from Jason Cramer. If not, try ConSpec in Tampa, FL. Im sure they'd ship you a tube.