Budman II

iTrader: (1)

I just need a quick answer here - I did a quick search but did not turn up the info I need. I am planning to run the 781 Mk IV heads on a .030 over Gen VI 454, and I need to know the correct head gasket to use. Do I need to use the Mk IV head gasket or the Gen VI gasket?

Thanks!

sonicss42

GenVI gasket. The sealing problem was on some GenV blocks with GenIV heads.

Budman II

iTrader: (1)

Thanks, Sonic. So, for a Gen VI block, it does not matter if you are running Mk IV or Gen VI heads, you use the Gen VI gasket, correct? If so, that makes things easy!

dogturd21

Sonicss42 is correct- I just refered to my Rebuilding the Gen V/VI Big Block Chevy Engines book, and it talks at great length about Mark IV heads on a Mark V block, but nothing about the Mark VI block.

Quoted from the book:
If you have a Mark IV head and want to use on a Mark V block, Victor Reinz offers a nitroseal gasket- pn 4918 for right side, pn 4923 left side.

Which brings me to my question- is there any practical difference between a head gasket for land use vs. marine use ? My thinking is no.

Budman II

iTrader: (1)

Hmmm. I checked the head gasket that was installed on my old Mk IV enginne in the boat (FelPro marine 17040) against the factory GM head gasket that came off of the Gen VI motor that I bought (GM 12554769), and for all intents and purposes, they were the same. I'll try to attach a couple of pictures.



The only real diffeence I could see in the pattern of them is on the ends - the Mk IV's had one extra opening, which happens to line up with one of the water jacket openings that both the Mk IV and Gen VI blocks have. Not sure why the GM gaskets have these passages closed off. I also thought it was interesting that the factory gaskets did not have a larger opening where the water jacket passages on the Gen VI are opened up from 3/4" holes to the triangular shaped openings. You can see the outline of these openings on the GM gasket.

dogturd21

Budman- you hit on the exact issus- cooling passage opening shape. Apparently if you use the wrong gasket, one side will cool too much and the other run too hot, causing accelerated wear and/or failure.

racinfever

Felpro #1037

apollard

Yes, there is. Marine gaskets use a good stainless steel as the core. Auto gaskets use plain steel, or at best cheap stainless, since they have corrosion protection in the cooling system. Using an auto gasket on a marine raw water cooled system will result in it rusting. Closed sysems could use auto gaskets, since they have the corrosion protection (antifreeze).

jeffswav

I have Mark IV heads on a Gen V block, I use the gaskets for Gen V . The marine gaskets use stainless steel, not sure if it is nessesary but I use them.

racinfever

felpro #1037