To add to bobwanna's comment. I've got a SW mechanical tach, 3 1/2" diameter. By removing the bezel and grinding down the lip of the case it slips right into the 'bird bezel. Then I carefully ground the plastic face to fit inside. Easy there, they melt on a belt sander. I'd bet the electric tachs use the same case.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

You should be able to find a old 2 piece cap mallory dual point tach drive somewhere, or if nothing else lathe one down from a different application. Would a sbc spin the same way? because those tach drive mallorys are all over.

I will assume you do not need to keep your car 100% original. I think another option is to find a small face electronic tach to install in place of the birds original mechanical tach. This would allow you to use say a 1959 292 distributor with mechanical and centrifugal advance for cheap. I recall this question on the early bird forum years ago and someone posted a source for the tach. I cannot recall source since it was a long time ago. 

Personally I would opt for the OEM dist with vacuum advance over the Mallory. It will always have a good resale value if needed. I suppose a machinist could cut up a 55 tach dist and graft on a 57 top but that would be quite an undertaking.

Good luck
Bob





AKA   Bob-93021

My information regarding the '57 Merc Turnpike Cruiser distributor is similar.  One small point is that the 368 engine distributor had a 13 tooth drive gear, not the 15 tooth that Jeff mentioned.  In any event, yes, swapping the distributor gear to a 14 tooth unit makes it usable in the 272, 292, 312 y-blocks.  I don't know how the vacuum advance and centrifugal advance distributor curves compare with what was used on the '57 'Birds.


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Steve.  The Mallory unit that is still in production for the y-block has no vacuum advance component.


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Thanks for the information, this site and the Y-blockers are always helpful. Currently looks like my options are Oldmics rebuildable 1957 tachdrive for $950 and a new Mallory unit for $851. Still not sure which option i will take.

Steve

Interesting to note that in 1957 there were 2 different part numbers used for tach drive distributors in the Y Block engines. This does not take into account any dual quad or supercharger distributor units.

The 2 different tach drive distributor part numbers were slated as a B7S 12127 A  and also a B7S 12127 D

Mercs , with the tachometer option 312 engines got the B7S 12127 D.

Thunderbirds (292 and 312s) could have gotten either the B7S 12127 A tach drive distributor OR the B7S 12127 D tach drive distributor units.

Curiously enough there was no specific tach drive distributor for the 292 engine.
The B7S 12127 A was cast as FEJ 12127 A
The B7S 12127 D was cast as FEK 12127 B

Oldmics

Greetings to all:  The 57 Mercury Turnpike Cruiser did have a mechanical tach but every TC I have seen had the Lincoln 368 Y block. They may have been available with a 312 but I have never seen one in a TC.   The 368 used the same distributor as the Ford Y but had a 15 tooth gear instead of a 14 tooth.  About 4 years ago I was very lucky to find a 57 Merc tach drive dizzy from a 368 in excellent shape very cheap. Changed the gear to a 14 tooth and am using it to run the mechanical tach in my restored 64 F100.  Sometimes it pays to look for the parts we want/need under totally different listings. Hope this helps, JEFF.........................



64F100 57FAIRLANE500

Back in '68 I went into the usual junkyard I got parts from, and the owner showed me a tach drive 57 dist. Said it came out of an ex police car he'd taken in. He owned an F code 57 bird, and he liked me. I suppose because I was usually covered in grease and willing to listen to his advice. " I'll put it under the counter kid, let me know when you can come up with 25 bucks". Took me a month, but he held it for me. That's the only reference I ever heard to a police car with a tach.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

the turnpikes all did.