39 Mercury FYI head gaskets

rockfla

rockfla

Well-known member
AFTER doing the head gaskets on our 39 Merc and using 59A head gaskets, I found this while looking for "other" stuff BUT these appear to BE the larger trapazoidal water jacket openings like originals for the 39 Mercury engine. Currently out of stock BUT Hopefully will have them back soon? https://www.edelbrock.com/cylinder-head-gasket-set-for-ford-7394.html
 

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Funny, that I just bought some of those from Rockauto for my merc engine. The middle hole is round on the merc. I ended up using 59A type gaskets. I'm not sure which motors have the trapezoidal centre hole.

Mine is a 39/40 99 engine.

Mart.
 
Typically the 39-42 Ford 221 cubic inch engines have the trapezoidal hole in the center.

Given the amount of water holes on the deck of a 38-48 engine (any of them), I would not worry about having the larger water holes in the middle. Frankly, I wish they were smaller and MORE water could be pushed to the rear of the engine (which is where the cylinders run hotter). This is most likely why Ford changed the water holes in the decks of 49-53 engines - with the larger water holes at the very BACK of the block.
 
I would be a bit concerned about the larger holes hampering cooling. The increased flow through the larger center holes might reduce the flow around the rear cylinders. Just looks like a short circuit to me, LOL.

If you consider the flow available through an opened thermostat, one of the gasket/block opens could provide that. Smaller holes, while still providing more combined flow than would be required for an open thermostat, might be better at distributing the flow through the block.
 
JSeery said:
I would be a bit concerned about the larger holes hampering cooling. The increased flow through the larger center holes might reduce the flow around the rear cylinders. Just looks like a short circuit to me, LOL.

If you consider the flow available through an opened thermostat, one of the gasket/block opens could provide that. Smaller holes, while still providing more combined flow than would be required for an open thermostat, might be better at distributing the flow through the block.
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I was talking with Mike at Third Gen when I first started to buy gaskets and the difference in the two gaskets. I think he said a couple of years after that Ford issued a "service bulletin" on this exact subject....thus the 59A smaller whole in the gasket actually worked better (OR just as good) for cooling??? (IF I understood him correctly)
 
Here is was is printed for the 39 Mercury. Also a shot of the water jacket design, I was told that you can also feel the difference in the "thickness" of the cylinder walls through the center water jackets.
 

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flatjack9 said:
That's not a Merc engine. Merc had a round hole in the center. What is the bore dia?
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Not sure what car this IS......BUT it is the engine that came in it. It was an Oct of 1938 production car and Judging by the oil and grime build up on the transmission and bell housing (near 1/4 thick in some spots) IF the engine was changed it was shortly after it was built and judging by all the fasteners and associated grim, rust, and such, it doesn't appear to have been changed. Also I can tell you, based on the current oil pressure (before head gasket replacement) the engine has been in this car a "LONG, long" time.
 

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Most engines have been through several rebuild or exchange cycles in the early years. If the vehicles were driven a lot the life expectancy of the engine was not than long. I would think it would be somewhat difficult to know if an engine was original.
 
I've never seen a 99 engine with anything other than the round hole in the center. Is the block stamped 99 on the right side? The Canadian ones have a raised 99 in the casting. Ford USA stamped the 99 on there to ID them for manufacturing. Eventually just the blue paint color was used to tell the difference.

The 221 engines of the 81A part number are the trapezoidal type with 3 1/16" bores. They can be bored out but not very far.
 
rotorwrench said:
I've never seen a 99 engine with anything other than the round hole in the center. Is the block stamped 99 on the right side? The Canadian ones have a raised 99 in the casting. Ford USA stamped the 99 on there to ID them for manufacturing. Eventually just the blue paint color was used to tell the difference.

The 221 engines of the 81A part number are the trapezoidal type with 3 1/16" bores. They can be bored out but not very far.
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Where on the block would the "99" be??
 
JSeery said:
Most engines have been through several rebuild or exchange cycles in the early years. If the vehicles were driven a lot the life expectancy of the engine was not than long. I would think it would be somewhat difficult to know if an engine was original.
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JSeery
It would be quite naive of me to "definitively" sit here say with 100% certainty that it is the original engine. I haven't rebuilt enough flatheads OR been around many that weren't in a car running SO my knowledge is limited at best and learning more as I go. I'm with you in that IF this engine is a replacement, as you say, its been quite a long time ago AND I think that in "most" cases the owners have no clue as to the "correct" engine. Case in point our 32 engine was removed for rebuilding back in the 60"s and the person who was charged with the rebuild kept it for his 32 roadster and installed a 34 motor in its place and the owners were none the wiser. In this case, it may well of had an issue and "whoever" did the work saw the "opportunity" for Merc engine over a Ford and "seized" an opportunity.....WHO knows. I don't know IF it matters OR IF Ford had a "lag" in 99 block production BUT as stated I know for a fact the car is a "Very Early" production car with-in the first 3 weeks of Production SO not sure "IF" that "Could" make a difference either!!!!
 
flatjack9 said:
Not all Merc engines had the 99 stamp. I have at least one of these.
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So Flatjack for lack of a picture this is how all 99 blocks were configured? And all "Ford" blocks of that era had the trapezoid center water jacket?
 

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They were usually stamped with the "99" on the front right side of the intake deck but not all of them were. This old thread from the HAMB has a lot of the information to ID the Mercury blocks. https://www.jalopyjournal.com/forum/threads/39-42-mercury-flathead-id.93447/

If there is no stamp and no round coolant port in the center of the deck, it is likely a 221 cid 81A block. The connecting rods are the only other way to confirm an early block. If it had 99A con rods then it is a 239.

An engine that passes the pencil test (pencil will rest on the block casting behind the timing cover) and has 48 or 91A type con rods (smaller bearings) then it is more likely a 221. They are otherwise completely interchangeable as far as bolting them into the engine compartment.
 
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