Have a head gasket(im 99.9% certain its the head gasket) thats weeping in the passenger side rear corner. Engine has not been run.

Machine work was done by a very reputable shop so I dont suspect anything there. Head and block were used, but inspected, although I dont know to what degree beyond visual for cracks.

Cometic MLS .040 gasket.

ARP 234-4317 studs torqued to 25-50-80 and small bolts torqued to 28 or whatever that spec is.

Steam ports are dry before anybody says anything about that. Plug for ECT port was pulled and resealed and is dry. Its definitely coming from the head gasket back between say the #7 and #6 bolt locations.

I have a replacement head gasket ready to go...

Anything to try before tearing into it to replace it? Should I crack all the studs loose individually and re-torque? Just bite the bullet and change it?

My buddy suggesting I put the vacuum coolant bleeder on it and see if it holds a vacuum(doubt it will).

 

I don’t think you’ll find anything wrong with the new headgasket on a freshly rebuilt, unstarted engine. Especially a Cometic. You’ve likely got a burr, or a deep scratch…or maybe even a crack, if you’re certain you’ve verified it’s not the steam vent or the cts hole plug.

 

im 99% certain its not a steam port or the ECT plug.

Im hoping for no cracks cause that would be catastrophic...

I dont remember seeing any burrs or anything like that, but its gotta come apart.

 

Best to re torque the heads after the first heat up cool down cycle if using non torque to yield fasteners. I assume you have gotten the engine up to operating temperature. If not do so and let cool down preferably over night. Loosen one fastener in proper sequence and bring back to torque. Loosen the next in sequence and bring back to torque. Continue until all are re torqued then do the same on the opposite bank. If the problem persists there is no option other than pulling the head and inspecting things further for flatness and surface finish. Cometics require a smooth surface finish under 50 RA. Any rougher than that they tend to **** coolant out the sides.

 

the car doesnt run. Needs to go to the tuner... so no it hasnt been run, as my OP says. I dont want to take the car to my tuner with a weeping head gasket and possibly have coolant blow out all over the dyno... I cant get the car hot without taking it to my tuner... so im in a cycle here...LOL. I already thought about trying to heat cycle it and see if it would seal, but I just dont think thats possible.

The shop that did the machine work is very well known LS shop in the country. Surface finish, while I dont know EXACTLY what the RA was, was damn good. They knew I was using Cometic MLS gaskets. I dont want to name that shop simply because I dont believe any of this is on them as far as their machine work.

 

Took the whole top and passenger side head off. Everything looked fine. Literally zero smoking guns. Sent pics to a few guys who said they didnt see anything either. My fab guy said "honestly looks like it never hit torque", which I have no clue as I torqued both heads with the same torque wrench at the same time(well I mean 30 minutes apart) so there "shouldnt" have been any difference. Talked to the shop that built bottom end and freshened heads and they agreed that it was possibly a fluke. He said clean head gasket well including blowing out between layers and check all holes for burrs that would keep the gasket from seating fully. I also noticed during my research that the GM gaskets have some type of rubber around most holes, my guess is to aid in sealing. The Cometic gasket I have does not have that and I assume relies on crush only to seal(or not seal)...

Put a new gasket on(Cometic .040) and sprayed it with copper, retorqued studs to 25-50-80. Got the rest of the motor re-assembled and refilled with oil. Spun the motor over a bit without the ECU on then decided to run the Haltech wizard again because I have installed fuel pressure sensor plus both O2 sensors... End of wizard is basically "attempt to start engine" or some such... well ****... she fired up. 2 months ago it wouldnt fire up(no O2's, but Haltech guys said not needed for idle). Im wondering if my fab guy wasnt on to something that it wasnt torqued properly(again I have no clue how or why not) and wouldnt make compression and thus wouldnt fire.

I ran out of time to put coolant in it, so ill do that Sunday before I take it to the tuner on Monday. Hopefully a new gasket with copper spray and re-torque will have solved it.