I know this has been asked to death but I did a search and couldn't find the numbers I was looking for. I know some of you guys have these numbers, so I'm asking for a little help. This is all for a stock 400 in a 1979 F-150. Thanks.

Piston dish cc's.
Valve relief cc's.
Deck height.
Compressed head gasket thickness and diameter(since it's bigger than the bore).
Combustion chamber cc's.

Also, for early 70's 351C 2bbl.-combustion chamber cc's

Am I forgetting anything to do some accurate compression ratio math?

Thanks again.

 

TTT

 

Ooops.

 

The bottom line is that you have to measure the actual parts you're using, if you want "accurate" calculations.

Larger cast iron parts (e.g., blocks and heads) have significant unit-to-unit variations due to the low-tech manufacturing processes and lax quality-control standards that were typical in the '70s. Any published "specs" are at best an average of several measurements, or far more likely, just an original design spec, which may not have been implemented in production. Published "specs" often went un-revised when designs changed, and even obvious typographic errors were repeated and went uncorrected for years.

So bearing all that in mind:

Average M-block (351M/400) cylinder head chamber sizes vary (from 75-80cc), depending on the casting ID, date, and foundry.

The nominal M-block deck height is 10.297", but again, to be accurate you'd have to measure the actual block you're using.

New gaskets can be had in various thickness. Stock gaskets I've measured varied from 0.025" to 0.040". Head gasket bore size is usually 4.10".

The stock 400 truck pistons I've measured had 13-14cc total clearance volume (including dish and valve relief).

If you want to do these calculations for an engine you plan to build, get the exact piston specs from the manufacturers. Aftermarket specs are usually more accurate.

If you really want "stock" numbers, you can plug in the known "spec" dimensions, and work it to the "spec" compression ratio of 8.4:1.