The Ford Barn

fisher · 07-29-2015, 01:05 PM

can you please
tell me what is good compression for my 1930 model A

Thanks
Fisher

Fullraceflathead · 07-29-2015, 01:07 PM

Stock? 50+psi

Bob Bidonde · 07-30-2015, 09:18 AM

A rule of thumb is to multiply the compression ratio by the atmospheric pressure. For example, the Model "A" stock compression ratio is 4.2:1, thus
14.7 psig x 4.2 = 61.7 psig. Generally, Model "A" engines will run well with cylinder pressures of 50 psig or more. A newly rebuilt motor should about 76 psig.

The difference between cylinders be none, or no more than 10% (about 7 psig).

There are two types of compression tests, dry and wet. In a wet test is done with 2 or 3 squirts of motor oil in in each cylinder. Wet compression readings should be higher than dry readings because the oil improves sealing of valves and rings.

Mitch//pa · 07-30-2015, 11:24 AM

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07-29-2015, 01:05 PM	#1
fisher Junior Member Join Date: Oct 2013 Location: Scotland Posts: 11	compression can you please tell me what is good compression for my 1930 model A Thanks Fisher

07-29-2015, 01:07 PM	#2
Fullraceflathead Senior Member Join Date: May 2012 Location: Chillicothe, Missouri Posts: 1,196	Re: compression Stock? 50+psi __________________ "If I asked people what they wanted they would have said faster horses." -Henry Ford "Primitive technology is not a design flaw" 1928 Ford Model A Roadster Pickup 1930 Gordon Smith Air Compressor 1941 Willy's Pickup 1960 Thunderbird-For Sale 1964 Buick Riviera 2x4 425 1965 Pontiac GTO, 455 Super Duty 2004 Dodge Ram SRT-10, V-10 Viper 1977 Charger Jet Boat,460 Ford,Jacuzzi Jet Front Engine Nostalgia Dragster,Supercharged 296 "Fullrace Flathead" Ford Engine Build up on DVD ask

07-30-2015, 09:18 AM	#3
Bob Bidonde Senior Member Join Date: May 2010 Location: Long Island, NY Posts: 3,498	Re: compression A rule of thumb is to multiply the compression ratio by the atmospheric pressure. For example, the Model "A" stock compression ratio is 4.2:1, thus 14.7 psig x 4.2 = 61.7 psig. Generally, Model "A" engines will run well with cylinder pressures of 50 psig or more. A newly rebuilt motor should about 76 psig. The difference between cylinders be none, or no more than 10% (about 7 psig). There are two types of compression tests, dry and wet. In a wet test is done with 2 or 3 squirts of motor oil in in each cylinder. Wet compression readings should be higher than dry readings because the oil improves sealing of valves and rings. __________________ Bob Bidonde

07-30-2015, 11:24 AM	#4
Mitch//pa BANNED Join Date: May 2010 Location: Bucks County, PA Posts: 11,454	Re: compression Sponsored Links (Register now to hide all advertisements) cheap gauges suck for accuracy