Walt Dupont--Me.
Well-known member
I was at a car show today. A guy had a beautifull restored to original 1940 Merc ragtop. The engine had 81-T on the head. Is that correct for a 40 Merc? I keep thinking that a truck head. Walt
40 Merc--81T---- on the heads
- Thread starter Walt Dupont--Me.
- Start date
flatheadernie
Senior Member
ford issued replacement heads for various applications used T to deignate . ernie n tx
What to look for on '40 Merc heads...
I have detailed the correct things to look for on '40 Mercury heads. Often, guys will have the "A" heads which are clearly, Ford - 85HP.
I hope the information below helps and clears up some common misconceptions.
95 H.P. (1940 Mercury)
The standard equipment cylinder heads were cast iron and had a compression ratio of 5.9:1.
Part #81T-6049 was cast into the very rear of the right cylinder head as well as directly below the large “T” on the face of the head. Part #81T- 6050 was cast into the very rear of the left cylinder head as well as directly below the large “T” on the face of the head. When the cylinder heads were installed the part numbers were closest to the cowl.
A large letter “T” was cast upon the face of each cylinder head. Drawings specified this “T” to be located between the very rear two spark plug holes.
The Ford script was cast into the cylinder heads approximately 1 ½” above the lowest row of stud holes in the center of the cylinder heads.
Actually, the "T" has nothing to do with replacement head part numbers.
I have detailed the correct things to look for on '40 Mercury heads. Often, guys will have the "A" heads which are clearly, Ford - 85HP.
I hope the information below helps and clears up some common misconceptions.
95 H.P. (1940 Mercury)
The standard equipment cylinder heads were cast iron and had a compression ratio of 5.9:1.
Part #81T-6049 was cast into the very rear of the right cylinder head as well as directly below the large “T” on the face of the head. Part #81T- 6050 was cast into the very rear of the left cylinder head as well as directly below the large “T” on the face of the head. When the cylinder heads were installed the part numbers were closest to the cowl.
A large letter “T” was cast upon the face of each cylinder head. Drawings specified this “T” to be located between the very rear two spark plug holes.
The Ford script was cast into the cylinder heads approximately 1 ½” above the lowest row of stud holes in the center of the cylinder heads.
Walt Dupont--Me.
Well-known member
Thanks Kube, accually this 40 Merc I looked at today had 81-T 6049 or 6050, I cain't remember, cast into the front of the left head. There was nothing in the middle or anyplace else on the head. I didn't look at the right head. Walt
Those sound like slightly later replacement heads. There were a few design changes in the period near the 40 Merc production. The heads installed on the line had the "T" cast into the front of them.
I have sets of the Merc heads and can send a photo if you like.
What color was the car you saw? Folkstone by chance?
I have sets of the Merc heads and can send a photo if you like.
What color was the car you saw? Folkstone by chance?
rotorwrench
Well-known member
"T" is for truck. A 1940 mercury would have most likely had 99T or C99A heads. At least I was always under the impression that the Mercury 99A (1939 & later Mercury models) was 100 horse like the 99T 100-HP 239 CID truck engine.
Kerby
PS: Another check of my books indicate 95-HP til 42 (29A). I wonder where the other 5 HP came from?
Kerby
PS: Another check of my books indicate 95-HP til 42 (29A). I wonder where the other 5 HP came from?
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Kerby, The information I posted above was found at the Benson Ford Research Center just recently. I am authoring the new '40 Ford book for the Ford Club of America and while researching many things I had come upon the info posted. Rest assured, the heads I described are for the Merc. The truck heads are in fact very similar. "T" being for truck is only partly correct. If anyone would like details of those, I can post it later today.
rotorwrench
Well-known member
I know the Mercury was an all new deal in 1939 so many changes always follow the first of anything. Also first year for the large type synchro rings in many 3-speed transmissions. Being the mercury was one of the first 239 CID motors I'm not surprised at the cross over with the truck types. I'm sure Ford took the advantage of the higher horse power for the trucks as well. I have never had an oportunity to check out the BFRC and wonder if the idea for the 95 HP was a mutual truck/Mercury thing from the outset or if one just led to the other? Also it seems many 99T motors had factory reliefs. I imagine that was to lower the compression a bit.
I know Ford sure took advantage of the later 337 Lincoln engine in the big Ford trucks after 1949 till the Y-blocks took over.
Kerby
I know Ford sure took advantage of the later 337 Lincoln engine in the big Ford trucks after 1949 till the Y-blocks took over.
Kerby
Bruce Lancaster
Member Emeritus
81 T were the originals; the 99T was used only on the actual truck version of the 99 engine.
The T is for truck (and an 85/221 truck at that!), but as pointed out above that is only part of the story. The vehicle use suffix on a part number designation (A for passenger, C for commercial, T for truck) only referrred to the first planned use of that part. If you look at engines, it is obvious that 98% of a 99A and a 99T are the same parts, and most of the tuck innards do in fact carry A prefixes.
The 81T was already in use at Ford when the 239 engines came along, and presumably that head was selected because it already had the chamber volume the designers wanted for the Merc. The truck version of the same engine presumably needed a volume not available from the parts bin and got entirely new heads, the 99T. Respective volumes are 84-86 cc and 90-92 cc.
ID ing a Merc engine block as correct is harder, and really requires measuring bore size and wall thickness...
Only real external mark was on most but not all '39-40 99 blocks, a roughly 1/4" stamping of "99" on front top surface...since this was stamped and not cast, it could easily be faked.
Otherwise 1940 221 and 239's look the same in terms of visible parts of block.
The T is for truck (and an 85/221 truck at that!), but as pointed out above that is only part of the story. The vehicle use suffix on a part number designation (A for passenger, C for commercial, T for truck) only referrred to the first planned use of that part. If you look at engines, it is obvious that 98% of a 99A and a 99T are the same parts, and most of the tuck innards do in fact carry A prefixes.
The 81T was already in use at Ford when the 239 engines came along, and presumably that head was selected because it already had the chamber volume the designers wanted for the Merc. The truck version of the same engine presumably needed a volume not available from the parts bin and got entirely new heads, the 99T. Respective volumes are 84-86 cc and 90-92 cc.
ID ing a Merc engine block as correct is harder, and really requires measuring bore size and wall thickness...
Only real external mark was on most but not all '39-40 99 blocks, a roughly 1/4" stamping of "99" on front top surface...since this was stamped and not cast, it could easily be faked.
Otherwise 1940 221 and 239's look the same in terms of visible parts of block.
rotorwrench
Well-known member
Bruce
That definitely make sense. I know the later 255 8CM Mercury heads and EAC heads had bigger chamber clearance for the larger 255 over the 239 CID engines to keep the compression ratio in the same ball park. The 81T heads must have done the same for the 239 VS the 221 CID engines. Where the Denver heads came in was anybodys guess.
Kerby
That definitely make sense. I know the later 255 8CM Mercury heads and EAC heads had bigger chamber clearance for the larger 255 over the 239 CID engines to keep the compression ratio in the same ball park. The 81T heads must have done the same for the 239 VS the 221 CID engines. Where the Denver heads came in was anybodys guess.
Kerby
Hi Bruce, Thanks for your comments. You obviously have done your homework!
Internally a 40 Merc block can be differentiated from the Ford as the Merc had a round water passage in the very center vs. the upside down 'keystone' shape of the Ford engine.
Bruce Lancaster
Member Emeritus
Also, a glance at the cylinder that is visible near the keystone hole will show the wall to be so absurdly thick you could distinguish it from an overbored 221 right there!
Merc 99/29 Folklore, awaiting confirmation: The "99" stamp on the top surface eventually disappeared. Folklore is that it existed to identify 99's on the assembly line, and was dropped when some genius came up with the idea of painting 239's blue. Probably right after an annoyed customer discovered he was missing a few inches in his new Merc...
Merc 99/29 Folklore, awaiting confirmation: The "99" stamp on the top surface eventually disappeared. Folklore is that it existed to identify 99's on the assembly line, and was dropped when some genius came up with the idea of painting 239's blue. Probably right after an annoyed customer discovered he was missing a few inches in his new Merc...
Bruce, your folklore theory about the '99' stamping is a good one. The problem with that theory is the fact that Mercury engines were painted blue from job #1 , 1939.
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