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Electrical to mechanical tachometer conversion kit
Has anybody tried this device or know of anyone using it and whether it works at all.
I just saw this mechanical to electrical conversion kit. Does this work is it any good? And if so I guess my friend could use the MSD distributer he already has.
A lot of folks have done it, and I have not read anything negative about it. Would solve the non tach distributor problem for you. It's a bit of work to pull the cluster is all, but that's not too bad once you remove the seat and pull the column.
I've done three of these conversions myself this year.. and I love the thing.
The only issue that I've had with all of the them is that the pre-set on the potentiometer is never close. You'll need to either do the conversion and take it somewhere to dial it in or send it to me before installation.
On my 1975-1977, 1978-1979 and 1980-1982 tach boards, they must be calibrated at 4000 rpms to be accurate. When we get the boards built, the first thing we do is run them up to 4k, dial them in and the rest fall in place (there is a reason to this madness).
I'm not sure about the reproduction conversion kit because I always hook the signal machine to them after I've done the conversion, and just like my boards (and out of habit), I flip on the 4k switch, dial it in and the rest of the readings fall in place...
Yeah, kind of a bummer unless you have a signal generator, but I'd hate to see someone do the installation and then find out the tach is not calibrated correctly. The other issue I have with this conversion kit that worries me.. the 1 turn pot on the board. It's a pretty low grade pot and considering the cost difference to upgrade to a 16 turn it kind of surprises me. On the imported china tach boards you can tap the pot and the output will change. I've not done this with the conversion kits to see what they do but the next one I install I'll do this. (one reason we used the 16 turn pot on our boards, they don't move or change).
i'm doing a 69 zr-1 clone right now and one of my guys in the shop did the tach conversion... I'm worried that he didn't test the tach on the signal generator (his comment was he didn't remember)... If that's the case we'll probably have to pull the left pad again to make the correct adjustment.
Willcox
Last edited by Willcox Corvette; Dec 11, 2017 at 10:01 PM.
I bought one of these kits for my 57. It is over 1000 rpms off. I emailed CC about it and got this answer: "This is calibrated for a "65-74 sweep/arc" If it needs to be adjusted, there is a screw. For use on 53-62 adjusting will be necessary with a signal generator." There were absolutely no instructions or mention of this with the kit. I don't even know what a signal generator is so or course I don't have one. can you leave the kit out of the dash but hooked up and adjust it to another known accurate tach or engine analyzer with an rpm read out to make the adjustment?
I don't know how the chip on the reproduction tachometer works, I've not had time to look at it or the number on the tach board to see how it's configured.
Our boards are calibrated at 4000 rpms and once we hit this it falls in place at 700-1000-2000 and 3000. If you try to dial a factory board in at 700 rpms the adjustment is so fine at the lower scale that you'll be 5-7 hundred rpms off at say 3000. The adjustment at the higher end scale is less precise and takes more adjustment on the pot to make the needle move.
But CC is correct, they will not work accurately out of the box and I don't remember reading the instructions because I have a signal generator. I also make one for sale as well. I just did one of these for a 60 and I hooked it up, went to 4k, dialed it in and everything was perfect.
What you might want to do is remove the tach from the dash, remove the movement from the metal can and then run power, ground and a signal wire from another tachometer. The square blue "POT" on the board is where you make the adjustment. Check the calibration then maybe take it up to 2000 and hold it and see how close it is to the other tach.
Tell you what.. you take it out, remove the movement from the can, ship it to me and pay the return shipping and I'll dial it in for you... No charge... Merry Christmas...
Willcox
Last edited by Willcox Corvette; Dec 12, 2017 at 04:23 PM.
I installed mine when I went to Holly HP FI.
I calibrated it just like Wilcox described. We hooked the signal wire to another car and calibrated it to that tach. It worked out fine.
The hardest part is removing the cluster. I have found that that job is made much easier by removing the peddle housing. After removing the steering column.
I installed mine when I went to Holly HP FI.
I calibrated it just like Wilcox described. We hooked the signal wire to another car and calibrated it to that tach. It worked out fine.
The hardest part is removing the cluster. I have found that that job is made much easier by removing the peddle housing. After removing the steering column.
I just saw this mechanical to electrical conversion kit. Does this work is it any good? And if so I guess my friend could use the MSD distributer he already has.
I thought the same thing, Frankie. A friend of mine owns a shop and convinced me to try this method. It is not that hard to remove (only about four nuts and two bolts) and makes routing the wires and cables much easier.
Another option which keeps the original tachometer is to use a Cable-X unit. These units take an electronic input and convert it to a cable output which just connects to your mechanical speedometer or tachometer. I have used two of these units for C1 speedometers and they work great. I asked the Cable-X folks about using this unit on a mechanical tachometer and they told me that it would work with a conventional ignition (input to the Cable-X is from the coil) or with the tach output on an EFI system. The output speed of the cable is adjusted by a set of DIP switches on the control box. The upside to this unit is that you do not have to remove the tachometer, assuming you can reach the cable connection on the rear of the tach. The downside to this unit is that you have to find a place to locate the control box and they are rather pricey ($400??).
Charles
I thought the same thing, Frankie. A friend of mine owns a shop and convinced me to try this method. It is not that hard to remove (only about four nuts and two bolts) and makes routing the wires and cables much easier.
Frankie, I know you're just dying to try this... be sure to take lots of pictures so we can all benefit!
I've done three of these conversions myself this year.. and I love the thing.
The only issue that I've had with all of the them is that the pre-set on the potentiometer is never close. You'll need to either do the conversion and take it somewhere to dial it in or send it to me before installation.
On my 1975-1977, 1978-1979 and 1980-1982 tach boards, they must be calibrated at 4000 rpms to be accurate. When we get the boards built, the first thing we do is run them up to 4k, dial them in and the rest fall in place (there is a reason to this madness).
I'm not sure about the reproduction conversion kit because I always hook the signal machine to them after I've done the conversion, and just like my boards (and out of habit), I flip on the 4k switch, dial it in and the rest of the readings fall in place...
Yeah, kind of a bummer unless you have a signal generator, but I'd hate to see someone do the installation and then find out the tach is not calibrated correctly. The other issue I have with this conversion kit that worries me.. the 1 turn pot on the board. It's a pretty low grade pot and considering the cost difference to upgrade to a 16 turn it kind of surprises me. On the imported china tach boards you can tap the pot and the output will change. I've not done this with the conversion kits to see what they do but the next one I install I'll do this. (one reason we used the 16 turn pot on our boards, they don't move or change).
i'm doing a 69 zr-1 clone right now and one of my guys in the shop did the tach conversion... I'm worried that he didn't test the tach on the signal generator (his comment was he didn't remember)... If that's the case we'll probably have to pull the left pad again to make the correct adjustment.
You know the more I think about it I think he would be best served in ordering a stock GM tach drive distributer, take it to a shop and have them fine tune the advance curve and keep the whole thing stock. He can sell off all that MSD HI-Performance kit (see below) billet distributer, the MSD 6-AL induction advance box in that kit, save maybe keep and use the MSD coil. Yeah its pretty and looks great but in reality this guy has a plain Jane run of the mill NOM rebuilt 350 that does NOT need 1,000,000 volts or any of that racer stuff... nor will his car truly benefit from all that stuff. The wiring diagram for the MSD 6-AL unit gives me a headache just looking at it. Maybe he can sell it off on E-Bay or some such website.
Last edited by Cali77l-82; Dec 13, 2017 at 01:58 PM.
I know the last one I did was popping around 5500 at 4k... I have no idea at the lower levels because I didn't check it. The next one I do I'll watch and see, I'm just used to dialing in our boards and I can only assume the 4000 dial in works for theirs, I'm just not sure.
That way he can ditch the coil, currently improperly mounted on his firewall and sell all that stuff and get some money to put towards whatever.
Originally Posted by Willcox Corvette
I know the last one I did was popping around 5500 at 4k... I have no idea at the lower levels because I didn't check it. The next one I do I'll watch and see, I'm just used to dialing in our boards and I can only assume the 4000 dial in works for theirs, I'm just not sure.
Electrical to mechanical tachometer conversion kit
If that's the case we'll probably have to pull the left pad again to make the correct adjustment. 
Maybe he can sell it off on E-Bay or some such website.
