Is it really 1.5" ? I made up some mounts out of 2X3 4.5" long just like the B&T book says. After that it says to drill a hole 1.5" in diameter 1.5" away from the end of the mount. Is that the correct hole size? I'd hate to waste these mounts by drilling the hole too big. I haven't bought my biscuit mounts yet so I'm really not familliar with how they work but I know the mounting hole in the water pumps is a lot smaller than 1.5". Following that book to a T has gotten me in trouble already, just seeing if somebody can confirm the size this hole has to be drilled.
1.5 in. is too big. It's 1 1/4 in. PM me you email address and I will email you a photo of an ***embled flathead biscuit motor mount in my 40 Ford.
I've seen some mounts that were even elongated to allow for the fudge factor. 1.25" would work for the 32 to 48 mounts as long as the centers were a close match up the the water pump centers. The rubber donuts are large enough so they shouldn't have issues at that size. Its not a bad idea to have some room to move just a little.
the hole size in a stock `32 front crossmember is 31/32" (.968") the shoulder that fits into these holes on the repro rubber part of the mounts is 7/8" , so there is about 3/32" clearance.
Attached are photos of how biscuits look when installed in my 1940 Ford frame and how they are ***embled. The pumps are 8RT truck pumps but regaular 8BA and Merc pumps will accomodate these biscuits. You will notice that the big flat flanged base washer goes in the hole that is in the frame (from the top) and the big piece of rubber etc. goes on top with the bolt and another rubber bushing that fits inside the flanged piece from the bottom. The dia. of the slightly raised part of the flanged steel washer is 1 1/4 in in dia. Therefore the hole in the frame is also 1 1/4 in. since that raised part must fit thru the frame. If you look at the other photos you will see how the entire motor mount and buisuit is ***embled with the red spark plug wire "pretending" to be as the metal frame of the car. To put you mind fully at ease take a piece of sheet metal, make a 1 1/4 in hole in it with a hole saw and you will quickly see that the hole must be 1 1/4 in NOT 1 1/2 in. Hope this helps. Motor mounts are available from many repro places like BOB DRAKE, DENNIS CARPENTER and **** SPADARO. HOT HEADS also uses them with their Chrysler kit. Also, this is the same biscuit set up as on a 51 merc except a "U" spacer is used as per photo. Hope this helps. 19Fordy
The late 49 thru 51 Mercury uses a different mount. It's similar to the 52 truck mount and the later 6 cylinder and 272/292 F-series pickup V8 mounts of the late 50s. The biscuits are larger in diameter. The lower mount is like the upper mount on the earlier 32 thru 48 set ups and the upper has the extended portion that goes thru the frame mount. These would probably work OK with a 1.5 diameter frame mount bore but may be loosey-goosey. The Bishop/Tardel book has a lot of questionable information and they admit that. It's a guide, not a blueprint.
The holes should be 1.25". I made the mistake of followed the B/T book and drilled 1.5". Like a dumb *** I didn't bother to measure the biscuit mounts sitting a foot away from my drill press.
Attached is a photo of 1951 Merc motor mounts and the front frame of a 51 Merc showing the holes where the biscuits go. The holes for the motor mount biscuits in the frame measure 1 1/4 in dia.
19Fordy Yer biscuits don't mach the drawing. Looks like you have the 48 to 51 truck mount biscuits there. Everything else is right on the money. the 8M-6038-B was a Mercury only item and was used with the 8M-6039 lower which evolved into the B9TT-6039-A lowers that are available today. Your upper looks like the lower in the drawing for the late 49 thru 51 Mercury mounts. The ones you picture look like the 51T-6038-A upper with the 59T-6039 lower.
Buy the biscuits first and go from there is you are doubtful of the hole size. It only take a few minutes to drill the hole whether the hole size is correct or not.
Also, brought up by the '32 mentions above, there are two flavors of early Ford biscuits: 1936 and back, 1937-48 and F type trucks. Diferent hole size needs. Aftermarket mounts like Hurst used the late type and these are most commonly used, but you need to know this when you dive into the Early Ford repro catalogs.
The 'fudge factor' is non applicable in this area. (unless you are using a 'flat-o-matic') The mounts have a lower metal pad that is stamped with a center protrusion to 'key' into the 1.25" motor mount bore. This is essential, for when the clutch is disengaged the engine and transmission are being pushed forward, essentially wasting some reactive action of the clutch pedal/T.O. brg travel. Factory cars and pickups with enclosed drivetrains had 'pre load adjusters ("stay rods") that connected the bellhousing to the "X" member legs. Engine mounts should be fitted to the respective hardware, to prevent fore-and-aft movement...
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