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rotorwrench · 08-02-2013, 01:25 PM

8BA blocks are all pretty much the same. If you pull the pan & look at the crank, it might have EAC or 1M casting marks. Earlier Merc cranks weren't marked. Measure the cheeks of one of the crank counter weights. Merc 4-inch is wider than Ford 3 3/4". Near 6-inches if I remember correctly. The clean out plugs on the con rod sludge traps are 5/8" diameter on most Merc 4-inchers.

Some of he French Simca SUMB & other French army truck engines had 6 7/8" con rods so they could all use the same pistons but FoMoCo only used the 7-inch con rods for the 8BA era so the Mercs generally use a special piston with different pin location on the skirt.

If you are using the engine for a 49 thru 53 Merc, the 8CM, 1CM, or EAC heads are OK but only if your stuck with the OEM Holley Load-A-Matic distributor set up. EAB heads are the ones to use if you want front mounted coolant return ports.

Many 8BA blocks have a rudementary date code stamped into the rear right side of the intake deck surface but not all do.

Any 8BA 9.5", 10", or 11" flywheel can be drilled to fit any of the other clutches a person would want to use. Most machine shops could do this for you and surface it to boot.

08-02-2013, 01:25 PM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,431	Re: Mercury Flatheads 8BA blocks are all pretty much the same. If you pull the pan & look at the crank, it might have EAC or 1M casting marks. Earlier Merc cranks weren't marked. Measure the cheeks of one of the crank counter weights. Merc 4-inch is wider than Ford 3 3/4". Near 6-inches if I remember correctly. The clean out plugs on the con rod sludge traps are 5/8" diameter on most Merc 4-inchers. Some of he French Simca SUMB & other French army truck engines had 6 7/8" con rods so they could all use the same pistons but FoMoCo only used the 7-inch con rods for the 8BA era so the Mercs generally use a special piston with different pin location on the skirt. If you are using the engine for a 49 thru 53 Merc, the 8CM, 1CM, or EAC heads are OK but only if your stuck with the OEM Holley Load-A-Matic distributor set up. EAB heads are the ones to use if you want front mounted coolant return ports. Many 8BA blocks have a rudementary date code stamped into the rear right side of the intake deck surface but not all do. Any 8BA 9.5", 10", or 11" flywheel can be drilled to fit any of the other clutches a person would want to use. Most machine shops could do this for you and surface it to boot.