The Ford Barn

Brian King · 02-14-2026, 11:26 PM

Hello all. I’ve got an old mechanical SW tach that I’m not sure if it’s any good. I’m thinking about going through it myself- any suggestions/tips? Thanks

cas3 · 02-14-2026, 11:29 PM

You have the drive? or the tach. Lots of old tachs around, the drive is the hard part to find

tubman · 02-15-2026, 10:45 AM

As to working on the tach head itself, I'd send it out to one of the speedometer guys to repair. I think it's full of springs and wheels, so be careful when disassembling if.

I found a NOS SW 5K mechanical tach. Luckily, I have an 8BA, so I found an SBC Mallory "flattop" distributor on eBay with an integral tach drive. I'm going to have "Charlie NY" convert it for flathead use. Then all it will take is the proper cable. (I think a readily available Corvette unit will work).

Terry,OH · 02-16-2026, 10:54 AM

The end of a Ford speedometer cable may fit the tach. If so, you can turn the tach with a drill to see if it has problems.

whygoby · 02-16-2026, 11:45 AM

The SW 674L tach drive is the best one to use when driving a mechanical tach. The ones with 90 degree mounting brackets are impossible to use,..... as the small flex cable driving the tach drive gearbox will work harden....and quit. The "direct drive" 674L is the best unit to use. I have sold 80 units over the last 12 years, and I still have a few from my last batch.

Brian King · 02-16-2026, 12:24 PM

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Appreciate the input all. whygoby, I sent you a DM.
THANKS!

solidaxle · 02-17-2026, 09:53 AM

Quote:

Originally Posted by tubman

As to working on the tach head itself, I'd send it out to one of the speedometer guys to repair. I think it's full of springs and wheels, so be careful when disassembling if.

I found a NOS SW 5K mechanical tach. Luckily, I have an 8BA, so I found an SBC Mallory "flattop" distributor on eBay with an integral tach drive. I'm going to have "Charlie NY" convert it for flathead use. Then all it will take is the proper cable. (I think a readily available Corvette unit will work).

The Corvette tach drive will work in a 8ba. You just have to have it modified for a flathead. Like Tubman, I use a Chevy Mallory flattop YZ with mechanical advance.

solidaxle · 02-17-2026, 10:02 AM

I used John Bordas in Texas for my Harley speedometer, he's a straight shooter and did a great job, very reasonable. I don't know if he does tachs. Give him a shout.
[email protected]

02-14-2026, 11:26 PM	#1
Brian King Member Join Date: Jan 2014 Location: Napa, CA Posts: 98	Mechanical Tachs Hello all. I’ve got an old mechanical SW tach that I’m not sure if it’s any good. I’m thinking about going through it myself- any suggestions/tips? Thanks

02-14-2026, 11:29 PM	#2
cas3 Senior Member Join Date: Jan 2011 Location: Beverly Kansas Posts: 5,557	Re: Mechanical Tachs You have the drive? or the tach. Lots of old tachs around, the drive is the hard part to find

02-15-2026, 10:45 AM	#3
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 12,132	Re: Mechanical Tachs As to working on the tach head itself, I'd send it out to one of the speedometer guys to repair. I think it's full of springs and wheels, so be careful when disassembling if. I found a NOS SW 5K mechanical tach. Luckily, I have an 8BA, so I found an SBC Mallory "flattop" distributor on eBay with an integral tach drive. I'm going to have "Charlie NY" convert it for flathead use. Then all it will take is the proper cable. (I think a readily available Corvette unit will work).

02-16-2026, 10:54 AM	#4
Terry,OH Senior Member Join Date: May 2010 Posts: 5,394	Re: Mechanical Tachs The end of a Ford speedometer cable may fit the tach. If so, you can turn the tach with a drill to see if it has problems.

02-16-2026, 11:45 AM	#5
whygoby Senior Member Join Date: May 2010 Location: Nevada Posts: 281	Re: Mechanical Tachs The SW 674L tach drive is the best one to use when driving a mechanical tach. The ones with 90 degree mounting brackets are impossible to use,..... as the small flex cable driving the tach drive gearbox will work harden....and quit. The "direct drive" 674L is the best unit to use. I have sold 80 units over the last 12 years, and I still have a few from my last batch. Last edited by whygoby; 02-16-2026 at 12:15 PM.

02-16-2026, 12:24 PM	#6
Brian King Member Join Date: Jan 2014 Location: Napa, CA Posts: 98	Re: Mechanical Tachs Sponsored Links (Register now to hide all advertisements) Appreciate the input all. whygoby, I sent you a DM. THANKS!

02-17-2026, 10:02 AM	#8
solidaxle Senior Member Join Date: Mar 2011 Location: upstate NY Posts: 538	Re: Mechanical Tachs I used John Bordas in Texas for my Harley speedometer, he's a straight shooter and did a great job, very reasonable. I don't know if he does tachs. Give him a shout. [email protected]