The Ford Barn

flatjack9 · 06-16-2012, 08:34 AM

EAC heads have a much larger chamber. Hence, lower comp ratio.

40 Deluxe · 06-16-2012, 04:17 PM

The larger displacement of the 255 Merc engine required larger chambers to keep the compression the same as the Ford 239, to run without detonation. The compression ratio was conservative to allow for bad gas, John Q Public lugging the engine, overheating, etc. Putting Ford heads on a Merc was a cheap way to get more compression and horsepower.

Ol' Ron · 06-16-2012, 05:20 PM

Just remember the Octaine rating of regular cas back in the late 40's was between 60-70 so 7.5 was a hi compression engine.

06-16-2012, 08:34 AM	#21
flatjack9 Senior Member Join Date: May 2010 Location: Oshkosh, Wi Posts: 1,348	Re: Compression Ratio EAC heads have a much larger chamber. Hence, lower comp ratio.

06-16-2012, 04:17 PM	#22
40 Deluxe Senior Member Join Date: May 2010 Location: Flagstaff, AZ Posts: 446	Re: Compression Ratio The larger displacement of the 255 Merc engine required larger chambers to keep the compression the same as the Ford 239, to run without detonation. The compression ratio was conservative to allow for bad gas, John Q Public lugging the engine, overheating, etc. Putting Ford heads on a Merc was a cheap way to get more compression and horsepower.

06-16-2012, 05:20 PM	#23
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 2,503	Re: Compression Ratio Just remember the Octaine rating of regular cas back in the late 40's was between 60-70 so 7.5 was a hi compression engine.

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