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john ancona 03-31-2025 06:04 PM

139 hp 302 ford help
 
1 Attachment(s)
Need help with the deck height , NHRA list a 302 at .047 Gasket ,and the deck height at .0005 is this correct

Dwight Southerland 03-31-2025 06:58 PM

Re: 139 hp 302 ford help
 
Yes.

john ancona 03-31-2025 07:36 PM

Re: 139 hp 302 ford help
 
1 Attachment(s)
Quote:

Originally Posted by Dwight Southerland (Post 711015)
Yes.

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

Mike Gray 03-31-2025 11:16 PM

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.

Dwight Southerland 04-01-2025 12:49 PM

Re: 139 hp 302 ford help
 
Quote:

Originally Posted by Mike Gray (Post 711021)

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.

Yes.

GTX JOHN 04-01-2025 07:34 PM

Re: 139 hp 302 ford help
 
Basically, a Zero Deck Piston for all practical purposes.

Larry Hill 04-03-2025 07:57 AM

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.

B/S 428 04-03-2025 12:32 PM

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

GTX JOHN 04-06-2025 10:36 PM

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.


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