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Old 07-23-2021, 12:06 PM   #1
427heaven
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Default How can I tell an early Merc v8 from Ford

Differences in Merc engines vs Ford engines?
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Old 07-23-2021, 12:25 PM   #2
tubman
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Default Re: How can I tell an early Merc v8 from Ford

There are two main ways : casting and stamping numbers or take them apart and inspect them. After all of the time that has passed since they were produced and all of the rebuilds and modifications that have taken place, the first option is very unreliable. Functionally, all that is really important is the displacement. Pre-war Mercury's were all 239 cubic inches (3 3/16" bore). Pre-war Fords were with a very few exceptions, were 221 cubic inches (3 1/16)" bore. From 1946 through 1948 (1947 in trucks) both marques used the 59A series 239 cubic inch engine. It gets a bit different from '49 on. The Mercury's from those years had 255 cubic inches, courtesy of the 4" stroke crankshaft, which is very desirable. Those engines will have "8CM" or "EAC" cast on the heads (the "EAC" being the '52-'53 models). Fords from those years will have "8BA", "8RT" (trucks), or "EAB" cast into them. this is the easiest way to tell, but again, is very unreliable because of the time and parts swapping in the intervening years. There are corresponding stampings on other parts, but again, the only way to be sure is to take it apart and inspect it. You can measure the stroke, measure across the crankshaft counterweights, or even look at the size if the clean-out plugs in the crankshaft. For very original engines, the color can be diagnostic; Early '49 Fords were green, later '49 through '51 were bronze, while '52-'53's were tangerine. The '49-'51 Mercury's were a bluish green. I can't recall the color of the late Merc's right now. I was luck enough to score an original '51 Merc a few years ago. It had all of the right numbers and was the right color. Of course it was a real Merc with the 4" crank. That doesn't happen very often.

This is just a general overview. If you have any specific questions, a search of the board will yield what you need. In the rare instance that it doesn't a question posted to the board will usually draw one or more answers in a short time.
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Old 07-23-2021, 12:27 PM   #3
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Default Re: How can I tell an early Merc v8 from Ford

The Mercury line started out with a 239 CID V8 in 1939 which had differences to the Ford 221 V8. After the war, all were 239 until 1949. The 8CM 255 CID engine shares most internal components with the 239 including the block but the crankshaft & pistons are 255.
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Old 07-23-2021, 12:31 PM   #4
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Default Re: How can I tell an early Merc v8 from Ford

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Differences in Merc engines vs Ford engines?
The '39-'42 Mercury engines were 239 cu. in. vs the same year Fords which were 221 cu. in. The Mercurys had a 3.187" bore, whereas the Fords had a 3.062" bore. In '46, both Ford and Mercury engines became identical to each other. SOME early Mercs had "99" identifiers stamped into the intake surface. Some subsequent Mercs got "99T" heads, whereas the similar-year Fords had "81A" heads. After the War II ('46-'48), they were both identical. DD
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Old 07-23-2021, 12:54 PM   #5
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Default Re: How can I tell an early Merc v8 from Ford

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Originally Posted by V8COOPMAN View Post
The '39-'42 Mercury engines were 239 cu. in. vs the same year Fords which were 221 cu. in. The Mercurys had a 3.187" bore, whereas the Fords had a 3.062" bore. In '46, both Ford and Mercury engines became identical to each other. SOME early Mercs had "99" identifiers stamped into the intake surface. Some subsequent Mercs got "99T" heads, whereas the similar-year Fords had "81A" heads. After the War II ('46-'48), they were both identical. DD
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The early Mercury's had 81T heads NOT 99T!!! At least 1939 to 1941. AND with in the 81T's there are "early" and "late" based on the water temperature threaded bung!!!
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File Type: jpg 81THeads-02.jpg (48.7 KB, 5 views)
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Old 07-23-2021, 12:59 PM   #6
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Default Re: How can I tell an early Merc v8 from Ford

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My 99 Merc has a 99 on that flat surface forward of the right hand head. It's a bit indistinct but it does say 99. Interestingly, when viewing the central exhaust port down through the holes in the deck face I could see a 99 there too.
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Old 07-23-2021, 01:04 PM   #7
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Default Re: How can I tell an early Merc v8 from Ford

427heaven
One "sort" of easy way and first identifier on the early Mercury block is a the "circle" water jacket outlet in the block as opposed to the "trapezoid" on a Ford block like attached!!! AND all the other info listed above with respect to measurements. I also think/heard with the round center holes the cylinder walls are much thicker feeling also??? Maybe those more versed on that aspect will chime in?????
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Old 07-23-2021, 01:11 PM   #8
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Default Re: How can I tell an early Merc v8 from Ford

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V8Coopman
The early Mercury's had 81T heads NOT 99T!!! At least 1939 to 1941. AND with in the 81T's there are "early" and "late" based on the water temperature threaded bung!!!

Quite true, although my feeble statement..."Some SUBSEQUENT Mercs got "99T" heads".....was meant to suggest AFTER the very first "81" renditions. I should have been MORE clear! DD
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Old 07-23-2021, 01:13 PM   #9
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Default Re: How can I tell an early Merc v8 from Ford

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Quite true, although my feeble statement..."Some SUBSEQUENT Mercs got "99T" heads".....was meant to suggest AFTER the very first "81" renditions. I should have been MORE clear! DD
Touche' my Friend!!!! Take good care as well!!!!
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Old 07-23-2021, 06:11 PM   #10
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Default Re: How can I tell an early Merc v8 from Ford

Why are some of the early Mercury engines sleeved down to 3 1/16” and have the smaller dia crank and rods?
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Old 07-23-2021, 10:54 PM   #11
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Default Re: How can I tell an early Merc v8 from Ford

Ford of Canada supplied the Australian & New Zealand Commonwealth countries. It is hard to believe that their Mercury engines would differ. From my research, I remember Canadian 99 blocks actually having raised "99" casting numbers. It's hard to say why a Mercury car would have a 221 in those early years. It certainly was not common to US built Mercury cars. Mercury pickups would be same as Fords.
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