7.4 Gen VI cylinder head gaskets

[wendellbee]

I have twin 7.4's Gen VI MPI's. These were distributed by Sea Max, so i cannot find much info on them. The engine serial nbrs are unreadable. The paperwork says they were produced in 2000 and installed in 2005. I just had the cylinder heads done on the starboard engine due to stuck valves from water in the oil. The heads did not need to be shaved. The dilemma i am having is what cylinder head gasket to use. The gaskets that came off are Chevrolet Performance Head Gaskets 12555728 with a .022 compressed thickness. The machine shop recommended a gasket with a compressed thickness of .039 and agreed I would lose some compression, but not much. My understanding is you lose .5 of compression for every 25% increase in gasket compressed height. Is there any advantage of going to a thicker gasket, other than better sealing.

 

[tpenfield]

Those engines are not all that high in compression anyway. The thing about the head gaskets is you want to make sure you are choosing one that has 'parallel' flow from the block to the heads. My understanding is that many of the automotive gaskets are designed to have sequential flow. I think on my engines, I was using the Fel-Pro 17042.

 

[alldodge]

Standard head gasket thickness for stock motor is .039 which will keep the quench right at .040. Reducing quench below this can create hot spots and damage the motor.

The gasket thickness can be reduced if the motor has been modified from stock, but we would need to know what was done, as in any changes to bore, stroke, pistons

As Ted mentioned, use a marine gasket not a auto type and the Fel Pro 17042 is also what I would recommend.

 

[wendellbee]

Standard head gasket thickness for stock motor is .039 which will keep the quench right at .040. Reducing quench below this can create hot spots and damage the motor.

The gasket thickness can be reduced if the motor has been modified from stock, but we would need to know what was done, as in any changes to bore, stroke, pistons

As Ted mentioned, use a marine gasket not a auto type and the Fel Pro 17042 is also what I would recommend.

I purchased the boat with these engines and the PO (2nd owner) knows nothing regarding the engines. Spoke to his mechanic and he has not done any work on the engines other than usual yearly maintenance. All I know, from paperwork found in the boat that the original engines were replaced in 2005 with these Sea Max motors, and they are stock. I'm aware these aren't high compression engines, but didn't want to lower the compression any more than what it is. according to GM these are marine gaskets. thanks for the info.

 

[Scott Danforth]

a standard felpro marine MLS gasket is what I would run.

Not sure I would run the GM gaskets unless its the marine ones.