cometic c5833?

[fe66comet]

I saw on a previous thread this gasket and had a question about the bore? The gasket appears to have the same bore as my block, is it OK to run it that that close? My bore is 4.080 already with an .030 over 390 piston. and .150 piston to deck at tdc.

[jayb]

Here's a couple of things to consider.  The top of the piston, above the ring, is slightly smaller in diameter than the bore, so this gives you some room to maneuver, even if the pistons come out of the bore at higher engine speeds.  Taking away from this clearance will be any piston rock, which could position the pistons closer or even in contact with the head gasket.  Also, if the head gasket does not match the bore PERFECTLY, you could have an overhang of several thousandths, or even more I guess.

Bottom line - if you want to use those gaskets, better figure on dummying up the reciprocating assembly and checking each piston for rock at the top of its travel, with the gasket installed on the block dowels.  You'd be safer going with a bigger bore gasket.

[KMcCullah]

With your piston in the hole .150, I think you would be ok.  I got these gaskets the other day  www.summitracing.com/parts/fms-m-6051-a427
Gonna try em with a std bore 390. Maybe they would work with your combo.

[fe66comet]

I live by the rule better safe than sorry, I can't afford the oops factor. I have far too much in it and I will put a lot of street miles on it when I am done so I am trying to take the bullet proof approach on my build so it will last. I have made some costly small block mistakes before but if I screw this one up it is 15 grand down the toilet. And back to square one one a two and a half year project so far. And that is just the engine. I figure 30 in it when I am done if I live that long LOL besides I can't be found on the road dead  that would be a disgrace to the FE heritage and as far as work trucks they have always treated me well. I never called a tow truck on my FEs just everything else.

[390 Cougar Conv]

If the fire ring is too close to the bore, I have seen the fire ring fall into the bore.  403 Olds were bad about this. If you chamfer too much at the top of the cyl. or there is too much chamfer it could cause the same problem.  I am in the assembly process and am nervous because I have 11 grand in my 390 so every thing I do  I check it twice.  Good luck with your build.  Clifford