MustangWorks.com : Ford Forums - View Single Post - miling block part II....compression ratio?

Jeff Chambers · 02-10-2003, 07:51 AM

I think your engine builder is a little off. A factory motor has the slugs .010-.020" in the hole. The nominal deck height is 8.200" to 8.210" (technically its 8.206"). Subtract from that half the stroke 1.500", rod length 5.090" and compression height 1.600", and it leaves the pistons at 0.020" maximum in the hole, 0.016" nominally and 0.010" minimum. I've always found them to be close to the .010" though.

With things zero-decked, a .043" thick gasket and 60.5cc chambers you're looking at just a hair under 9.5:1.

I've got a compression ratio calculator on my site under the Tech Articles section if you'd like to run the numbers yourself.

02-10-2003, 07:51 AM	#2
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	I think your engine builder is a little off. A factory motor has the slugs .010-.020" in the hole. The nominal deck height is 8.200" to 8.210" (technically its 8.206"). Subtract from that half the stroke 1.500", rod length 5.090" and compression height 1.600", and it leaves the pistons at 0.020" maximum in the hole, 0.016" nominally and 0.010" minimum. I've always found them to be close to the .010" though. With things zero-decked, a .043" thick gasket and 60.5cc chambers you're looking at just a hair under 9.5:1. I've got a compression ratio calculator on my site under the Tech Articles section if you'd like to run the numbers yourself. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"