139 hp 302 ford help

john ancona · 03-31-2025, 06:04 PM

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

Yes.

john ancona · 03-31-2025, 07:36 PM

Quote:

Originally Posted by Dwight Southerland

Yes.

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

Mike Gray · 03-31-2025, 11:16 PM

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

Quote:

Originally Posted by Mike Gray

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

Basically, a Zero Deck Piston for all practical purposes.

03-31-2025, 06:04 PM	#1
john ancona Member Join Date: Mar 2006 Location: California Posts: 186 Likes: 3 Liked 179 Times in 52 Posts	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 Attached Thumbnails __________________ John Ancona 717 STK / SS

03-31-2025, 06:58 PM	#2
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 1,999 Likes: 64 Liked 772 Times in 192 Posts	Re: 139 hp 302 ford help Yes. __________________

03-31-2025, 11:16 PM	#4
Mike Gray Senior Member Join Date: Oct 2006 Posts: 614 Likes: 308 Liked 685 Times in 196 Posts	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. __________________ Mike 7570 A/SA Last edited by Mike Gray; 03-31-2025 at 11:29 PM.

04-01-2025, 07:34 PM	#6
GTX JOHN VIP Member Join Date: Jun 2009 Location: Boulder City, Nevada 89005 Posts: 2,727 Likes: 2,780 Liked 2,460 Times in 693 Posts	Re: 139 hp 302 ford help Basically, a Zero Deck Piston for all practical purposes. __________________ John Irving 741 Stock 741 Super Stock