Little67red

Just put my 327 together.as I was cleaning up my mess I picked up rapper from head gasket.it said for 400sb they sent wrong gaskets.the engine is all together.will I have a problem with that head gasket.

leif.anderson93

The difference between the 400 and the 327 are steam holes for cooling due to the siamesed bores on the 400. The 400 gaskets should work but you'll have an area around the cylinder, that the bigger gasket bore, will leave exposed.

Westlotorn

It will reduce your compression a little as the 400 is a 4.125 bore and the 327 is a 4.000 bore. Could you run it, yes, I think I would change it out for the proper size. Fel Pro 7733PT2. Or you can get the thin steel shim gaskets like the factory used and raise your compression a little more. Running that oversize gasket will leave some un burned fuel in your cylinders every time the engine fires, a very small amount but you pay for fuel, might as well burn it for power rather than exhaust waste.

Sky65

What part number gaskets did you use? It's not unusual for manufactures to include the 400 in fitments for in all sbc even though they don't.

Tom

Little67red

I ordered for 327. Don’t remember part number.they sent me part number fel-pro 8364pt.I don’t know if they will work but they are staying on.I am not going to take it all a part.wish me luck.

3154tm

can't speak to how accurate this is but it will allow you to play with head gasket bore diameter to see the effect on compression ratio.
https://diamondracing.net/p-10-compr...alculator.html

Sky65

Well it looks like that gasket is specifically for a 400 and has steam holes. I don't think steam holes will be a problem but as someone already said the bore diameter is larger than stock reducing compression some degree. If it runs ok I wouldn't mess with it unless it becomes a problem. JMO.


Tom

Westlotorn

The Fel Pro 7733PT2 has a bore size of 4.125, the Fel Pro 8364PT has a bore size of 4.190

So the 400 gasket in this case is .065 larger bore than a 327 gasket. Both are nominally .039 thick. The use of the 400 gasket is not fatal, it will work, you are just leaving some performance on the table.
If you don't run for maximum power you might never notice the gasket change. I doubt the change would net more than 15 HP if corrected.

7733PT2 picture

BrandonU

The head gasket must fit the combustion chamber as well. (Either the bore or chamber, whichever is larger.) Without mention of the head used, you need to look close there. No portion of the gasket can extend into the chamber or bore and survive or create detonation issues. This is why you see non-round head gaskets. Typical SBC in stock trims will be about 4.100-4.125". The steam holes only matter if the block and heads are drilled for them.

Brandon Unklesbay
All-In Performance, LLC

Little67red

The engine is 30 over.so I been thinking it’s probably not as bad as I thought.