cometic head gaskets

[RICK W]

What is the proper head torque for a 350 super stock motor with .036 cometic head gaskets with studs, they are seeping at the corners at 75 lbs. Thanks

[Alan Roehrich]

That isn't a torque problem, most likely. More apt to be warpage or finish. Adding torque is not the solution.

[Ed Wright]

Originally Posted by Alan Roehrich

That isn't a torque problem, most likely. More apt to be warpage or finish. Adding torque is not the solution.

I have used & reused those for a few years now, with no issues. I'm with Alan.

[FED 387]

Have you ever checked the block and head for flatness? Recently? Also Cometic will tell you to use the "torque specs " that the head bolt or head stud manufacturer recommends SBC usually is 65 but if you are using ARP because of the lube they use to install the studs I'm sure you have to go higher --Even tho Cometic does not recommend it have you tried re torquing the heads to see if they are in spec just in case you mighta missed one-- However if its the ends leaking most likely the heads are not truly flat and might need to be resurfaced--FED 387

[Ed Wright]

^^^^^^^ Never heard of anybody using 75 lbs either.

[RICK W]

Removed intake, leaking in the middle inside also, deck surface too rough for those gaskets I suspect

[Ed Wright]

Originally Posted by RICK W

Removed intake, leaking in the middle inside also, deck surface too rough for those gaskets I suspect

They need a smooth finish. I have seen corner automotive machine shops with cutters on their head & block miles set up for a rough finish. Ridges. Not what we need.

[ss3011]

This is a question on what to do about this problem . If its found that the surface finish is too rough , what can be done to correct this or make due with it . I am thinking that the engine has already been setup with the correct deck height and combustion chamber volume so if the block was re-decked, to correct the surface finish, then it might not pass tech , same with the heads . Can some sort of sealer be used like Permatex Copper Gasket Sealer ? I recently disassembled an engine with Cometic head gaskets and there was no gasket sealer on the head gaskets . Is this normal for Cometic gaskets ?

[BillK]

Originally Posted by FED 387

if you are using ARP because of the lube they use to install the studs I'm sure you have to go higher

Fed,
Actually using the ARP lube typically requires LESS torque on the same fastener. A torque wrench basically measures friction and the ARP lube makes less friction so it requires less torque to get the same stretch on the fastener.

That being said, the torque shown for ARP head studs with their lube is 80 ft lbs so if the Rick only torqued them to 75 that is really not enough. Also depends on the brand of studs and what lube was used on them.

[BillK]

Rick,

Are they ARP studs ? Did you use ARP lube or just oil ? If they are ARP studs the torque spec is 80 lb ft with ARP lube. If you used oil it would be higher.

I personally think that the finish would really have to be bad to make them leak. If you could see some of the factory cylinder head finishes that I see you would understand why I say that. They are pretty terrible yet they don't leak. I always put the proper finish on them when I machine them but I don't know if it is your problem.

Now if the deck or the heads have low spots in them I could see it.

Years ago one of the Fel Pro performance engineers told me to do the following when torqueing race engine heads.
1. Torque the heads as usual to the correct torque.
2. Let them sit overnight
3. Start with the first bolt in the pattern, loosen it 1/2 turn and then torque it back to specs in one step. Continue through the pattern one bolt at a time doing the same thing.

This method works much better than just putting your toque wrench on and re-torqueing the fastener because typically the breakaway torque to get the bolt or nut moving again is a lot more than the final torque spec.

If you try this, mark one of the bolts or nuts before you loosen it. Then re-torque it and see how much more it turns. I typically see close to 1/8 turn.

I do this on almost every engine I do and have basically not had any head gasket issues.