Head Gaskets?

Neelsonwheels

Neelsonwheels

Donating Member
I recently had a problem pressurizing the coolant system on my truck. After exhausting all
other possibilities I came to the conclusion that I have a head gasket breach. I tore the engine down to the block and took the heads to the machinist to have them checked out. They were pressure tested,cleaned,and checked for flatness. They are back and are all set. The machinist inspected the gaskets and stated that the pass. side fire ring never seated. You can see that the ring is not shiny like the ring on the drivers side. I don't know or care how this happened. Incorrect torquing of the heads. Overheating. Whatever. My question is how do I know what Cometic gaskets to order for replacement. Can I measure them with a vernier for thickness? Also my engine is bored 0.030 over. Any help would be great!!
 
RealFastV6

RealFastV6

@jb_and_his_coffee
Re: Head Gaskets?

Cometic MLS, P/N C5739-040.

You can measure the old gasket. It'll probably be .040, but the next closest are .035 and .045. The number after the dash in the PN is the thickness.

I know there's lots of opinions about dry vs wet and whether you need to retorque. I go with the copper spray sealant and retorque after 24hrs. I haven't done enough of them to have my own opinion but that's from my bud whos done his fair share, and that's how I did my Ty, and no leaks yet.
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: Head Gaskets?

spray on all surfaces? or just top and bottom? I mean head contact side and block contact side. With the copper spray.You have head studs or bolts? Thanks for the help>
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: Head Gaskets?

RealFastV6 said:
Cometic MLS, P/N C5739-040.

You can measure the old gasket. It'll probably be .040, but the next closest are .035 and .045. The number after the dash in the PN is the thickness.

I know there's lots of opinions about dry vs wet and whether you need to retorque. I go with the copper spray sealant and retorque after 24hrs. I haven't done enough of them to have my own opinion but that's from my bud whos done his fair share, and that's how I did my Ty, and no leaks yet.
Click to expand...

Doesn't retorque break the seal of the RTV on the head bolts?
 
Don W.

Don W.

Stab it and steer it
Re: Head Gaskets?

Cometic requires a certain smoothness on the block and heads.

http://www.cometic.com/technical.aspx

I run Cometic. 0.030 over bore. 0.038 on the thickness. I torque to a 2-4 lbs over factory to allow for torque wrench error. I use red RTV on the threads and don't re-torque. Cometic says to install clean, that's the way I do it. The gasket that is on the pas side has been reused once. (Still there.) Since the drivers side had already been reused once it was replaced during my recent piston replacement. Not cheap but I can't complain. I'm at around 20# boost. Racing almost weekly.

Only head gasket I've ever blown on this truck was a stock one. Don't remember what I used before the Cometics but they held.

RE the 0.038 thickness. It's my understanding from my machinist that Cometic will make whatever you order. 0.038 is not on the web site, he had to call.

My question is how does one fire ring not seat? Did the other 5 look "seated?" Whose gaskets were the old ones? Seems strange. A pic if you still have the old gaskets would be nice.

Otherwise that's my :2cents:
 
RealFastV6

RealFastV6

@jb_and_his_coffee
Head Gaskets?

Bolts, and teflon thread sealant not RTV.

Copper on gasket not directly on block or heads.


Sent from my iPhone using Tapatalk.
 
Don W.

Don W.

Stab it and steer it
Re: Head Gaskets?

RealFastV6 said:
Bolts, and teflon thread sealant not RTV.

Copper on gasket not directly on block or heads.


Sent from my iPhone using Tapatalk.
Click to expand...

Copper? Makes no difference to me but Cometic says dry because there is a Viton (I think it said) coating on them. I suspect if it, the copper, is real thin it would work. Just that for the money they get I'd rather follow their instructions...:roll:

Interesting on the teflon. Tape or some other version? Little late for me on this install but with teflon I wonder if you're getting a "better" torque reading?
 
D

Damian

Member
Re: Head Gaskets?

Neelsonwheels said:
What are you running for boost? What your engine build? Stockish?
Click to expand...

Stock motor with JE pistons and I ran 20psi with my GT37 and they are still holding up just fine. They are MLS head gaskets. They do have a coating on them, don't recall what it was though.
 
Neelsonwheels

Neelsonwheels

Donating Member
Re: Head Gaskets?

LOL Justen,

I was referring to the head and block mating surfaces of the head gaskets and not the inner
Thicker metal layer of the gasket
 
syclone3

syclone3

Member
Re: Head Gaskets?

Hard to beat the Permatex copper spray. Both sides of the gasket. I used ARP head studs. Been using them on everything for over 25 years. If you are using headbolts. I like the Permatex carmel looking sealer. White container with the brush. Never used RTV on bolt threads before.
 
Aeroking

Aeroking

e.i.
Re: Head Gaskets?

My method is the same as Justin above. I've been reusing the C5739 Cometics 3 times so far. I give them a good clean and inspection, then a fresh coat of Permatex copper spray both sides, and let it tack up.
 
mattw

mattw

Active member
Re: Head Gaskets?

I used that felpro gasket on my new build. Was recommended by the builder.. The engine isn't installed yet but should be next week..

MLS%20Head%20Gasket.jpg
 
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