139 hp 302 ford help
 

Need help with the deck height , NHRA list a 302 at .047 Gasket ,and the deck height at .0005 is this correct

Re: 139 hp 302 ford help
 

Yes.

Re: 139 hp 302 ford help
 

Thank You for the help
so the piston is five tenths above the deck

Re: 139 hp 302 ford help
 

Negative vs. Positive Clearance:
Negative clearance means the piston protrudes slightly from the deck surface, while positive clearance means the piston sits a bit inside the cylinder bore.

The .0005 on the chart appears to be a positive number so the piston should be below the deck. I assume if it’s assembled .0005 above a .048 gasket gets you back to correct deck clearance.

Re: 139 hp 302 ford help
 

Yes.

Re: 139 hp 302 ford help
 

Basically, a Zero Deck Piston for all practical purposes.

Re: 139 hp 302 ford help
 

For longevity of the block it might be best to start with a deck clearance of .010 to .015 if gaskets are available to bring the number to .048. If is easier to skim cut the block in the future than to shorten the rods or de-stroke the crank to get to the legal numbers.

Re: 139 hp 302 ford help
 

The early 302 blocks (68-72) deck height are about .020 lower than the 73 and up 302 blocks so with a early block you're close to 0 deck height and with a later block you're about .020 in the hole. Brian Seaberg 627

Re: 139 hp 302 ford help
 

Cometic has always made us whatever thickness gaskets we needed
to get deck and gasket height whatever we have need to be legal.