Author Topic: Mechanical Tach Drive  (Read 1389 times)

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frnkeore

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Mechanical Tach Drive
« on: September 18, 2022, 01:43:08 AM »
I've always like mech tach drives and since I have the one, for my 361 industrial block, I've decided to use it, with a Smiths tach.

Has anyone used one in their eng?

It's has a single point cam and I will use a PerTronix conversion but, if there are better ones, please tell me about them. I've heard there can be issues with the PerTronix, I'd like to hear about those, also.

The 391/industrial dist, is about a inch taller than a std dist, that's because part of the governor is below the breaker plate and pulls vacuum through the shaft, to operate a spring loaded weight. It also allows me to use the 5/16 drive and oil pump. 

I took it apart today, removed the governor assy and it's soaking, to clean it up. It doesn't look any different than a std points dist, from the weights up.
Frank

bsprowl

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Re: Mechanical Tach Drive
« Reply #1 on: September 18, 2022, 09:23:47 PM »
The '58 Edsel had a mechanical tach option with the 361.  I've got one but it is in a storage unit (pending completion of my shop).  I don't think it is any taller than a standard distributor.

frnkeore

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Re: Mechanical Tach Drive
« Reply #2 on: September 19, 2022, 12:53:09 AM »
Yes, I'm familiar with those. In '63, I had a '58 Corsair (410 MEL) with one. They had 5k tach's, on the far left of the dash. The '58 Edsel's had a huge amount of options. Possibly, more than any other '58 FoMoCo car.

This is one from a truck or industrial eng. It's both taller under the cap and also taller beneath that area. It is overall 6" tall 3"+ taller than the std car dist.

Something that I can't find, even though I have a '75 & '78 truck manuals, is the total centrifugal advance or all in advance rpm. Since these are only 3600 - 3800 rpm engines, it may come in a little sooner than the cars.
« Last Edit: September 19, 2022, 01:56:34 AM by frnkeore »
Frank

cammerfe

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Re: Mechanical Tach Drive
« Reply #3 on: September 19, 2022, 12:35:22 PM »
FWIW, Mallory used to make mechanical-drive distributors. You might be able to find one, and use it with the most modern 'guts' via a conversion. The last time I looked, there were a variety of those quite available.

KS

BigBlueIron

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Re: Mechanical Tach Drive
« Reply #4 on: September 19, 2022, 03:02:27 PM »
Converted one just like you describe but it was for use in industrial application, it did not have the tach drive but the boss was in the distributor for one. Used the Crane XR-I as it offered the lowest rev limiter (4000). Has been working fine last 7 or 8 yrs but I don't think its available anymore since Crane was bought up.  Fit up was the same as a regular points distributor.

Pertronix, just make sure you have a good ground and a clean 12v.

I wouldn't worry about how the weights and springs were setup from Ford, set it up the way you want.

gregaba

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Re: Mechanical Tach Drive
« Reply #5 on: September 19, 2022, 05:48:14 PM »
I have one of those off a truck engine some where in my shop. If I can remember i will check it out. I don't remember it having a governor on it.
I all so have a mallory and an excell tack drive distributor's.
Greg

frnkeore

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Re: Mechanical Tach Drive
« Reply #6 on: September 19, 2022, 06:57:57 PM »
Thank you, all for your input.

The breaker plate is exactly like the std car dist so, anything that will work, inside a FE single point dist, will work on this. It's just about 3" taller.

The way the governor part of these work, is that the vacuum is pulled into the dist housing, between seals and goes up, threw the center of the shaft, to a spring loaded weight, that controls the amount of vacuum that can pass, threw it and in the housing area of that weight, under the breaker plate, it vents back to the air cleaner.
« Last Edit: September 19, 2022, 07:05:06 PM by frnkeore »
Frank

TomP

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Re: Mechanical Tach Drive
« Reply #7 on: September 26, 2022, 12:29:06 AM »
I use a mechanical tach with a Mallory distributor from a marine 427. I first ran it dual points then converted it to cut down electronic guts.  The 60's Stewart Warner mechanical tacn is dead accurate, just can't have a shift light as easily.

frnkeore

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Re: Mechanical Tach Drive
« Reply #8 on: September 26, 2022, 12:20:58 PM »
Thanks, for that. I'll keep my eye open for a SW.

What is the gear ratio on yours, 2/1 or 4/1?

I don't use a shift light, I set the tach, in the line of site, so that the needle is straight up to shift.
« Last Edit: September 26, 2022, 12:24:46 PM by frnkeore »
Frank

RJP

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Re: Mechanical Tach Drive
« Reply #9 on: September 26, 2022, 02:37:51 PM »
Thanks, for that. I'll keep my eye open for a SW.

What is the gear ratio on yours, 2/1 or 4/1?

I don't use a shift light, I set the tach, in the line of site, so that the needle is straight up to shift.
Don't overlook the Jones/Motorola mechanical tachs. Can be found at swap meets usually taken from hot boats. Very accurate and durable.

frnkeore

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Re: Mechanical Tach Drive
« Reply #10 on: September 27, 2022, 11:12:53 AM »
Who makes the Moroso tachs?
Frank

machoneman

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Re: Mechanical Tach Drive
« Reply #11 on: September 27, 2022, 12:29:00 PM »
It used to be Jones/Motorola. Had one, very accurate even to near 9K in a old racer. Very durable too.
Bob Maag

frnkeore

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Re: Mechanical Tach Drive
« Reply #12 on: September 27, 2022, 12:32:10 PM »
Thank you. I have a opportunity to buy a 12k one.
Frank

475fetoploader

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Re: Mechanical Tach Drive
« Reply #13 on: September 30, 2022, 02:33:28 PM »
Somewhere in my dad's shop there's an old I think Accel dual point tach drive, and a Moroso 10k tach.  I wonder if I could convert the distributor to electronic, and put that in the Fairlane. He had it in his 64 Fairlane, and in the 75 F-250 Im restoring.  I better go visit.
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Heo

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Re: Mechanical Tach Drive
« Reply #14 on: October 14, 2022, 12:43:02 AM »
If the breakerplate and shaft is the same as a points distributor
you may be able to convert it to duraspark parts



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