1941 Mercury motor question

[Bruce Compton Canada]

I have a rebuilt '41 Merc motor ( actually has around 500 miles on it) that I purchased with aluminum finned heads. I'd like to put the correct cast iron heads back on it but don't know if there were specific heads for the Merc., or did they use Ford heads? Thanks : Bruce

 

[bobscogin]

I have a '42 Mercury motor and the heads have "29A" cast into them. That's the same as the model number for the '42 Mercury, so it leads me to believe the heads are specific to that model. I won't say that there are Mercury specific heads for all Mercury models, but it seems to be true in this case. Functionally, they're probably interchangeable with Ford heads, possibly with minor differences in chamber volume. Not sure.

Bob

 

[ford1]

i have a book on older mercs and it say its should have 19a stamped on them

 

[Karl Wolf]

If you're looking for a set of heads that will work, make sure you get a set that came with a block bore size of 3 3/16" ... Check for valve clearance, put the heads on loose with no gaskets and turn crankshaft by hand a few times... 59ab heads ought to work... Karl

 

[42ford]

I have a '42 Mercury motor and the heads have "29A" cast into them. That's the same as the model number for the '42 Mercury, so it leads me to believe the heads are specific to that model. I won't say that there are Mercury specific heads for all Mercury models, but it seems to be true in this case. Functionally, they're probably interchangeable with Ford heads, possibly with minor differences in chamber volume. Not sure.

Bob

I have 1 NOS 29A head. I would swap it for the same 21A. Both are for 42 Merc = 29A and Ford + 21A

 

[rotorwrench]

I think the 41 Mercury may have had the 99T heads and early Mercs had 81T if I remember correctly. I suppose they used the truck heads to keep the compression ratio the same as the 90 HP engines. The 29A heads may have been used in some 1941 production and would have been on the 1942 and a number of military 239 CID 100 HP engines during the war as well, at least until 1945 anyway. The 59A types were a direct replacement for the older 239 CID engines.

PS: Ford did make 99AS and 19AS heads that were not listed in the 28 thru 48 Ford Chassis Parts Catalog and they are known as the "Denver" high compression heads. They are also likely candidates for an early Mercury 239CID motor. They might be a little difficult to find and will be pricy if you do. Some of the Canadian made heads of the era like the C99A types could also be good candidates especially if you want high compression but they are aluminum.