I have a 58 corvette that has been changed to a late madel gm alternator set up, the tach is connected to a tach drive distributor, it is not correct, is there a way to calibtate the original 58 tach to a distributor drive?
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Re: tach on 58 vette
A speedo shop should be able to do this. If you notice there should be the words " reads half cable speed" printed on the back. -
Re: tach on 58 vette
Until recently you could order a tach head from any of the major vendors. They could be had in either configuration, ie "reads cable speed" or "reads twice cable speed". What you need with the distributer drive is "twice cable speed". Despite the fact that AC no longer services these, there are no doubt still some around. Check with an AC service center. They MAY be able to recalibrate your existing head.
Another alternative, which may be more cost effective is to convert your existing tach to electronic. I understand some of the Corvette instrument repair shops do this.
It's not out of the question to find the necessary parts to convert back to a generator driven tach. Check with generator repair shops in your areaa to see if one has an old core with the extended shaft. These were pretty common at one time since the same generator was used on full size Chevys with power steering. If you can locate one of these, the rest is pretty easy and fairly cheap. The tach drive units are reproduced and not terribly expensive.
I got a generator for my 62 at one of these type shops. I had to hunt through a million old generators to find one the right configuration, but once I had the core all I paid was the rebuild charge ( $70) and a $10 core charge.Comment
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One slight glitch
is that the 58 has the rev counter. The tach heads that were available until recently I believe were the 59-62 only style.Comment
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Re: One slight glitch
I'm not sure of the spline size but a Chevette with a diesel engine had an alternator with spline out the back like the old generators did . I just can't remember what it drove, I think it was from a vaccum pump for power brakes . Maybe you could have your cake and eat it too.Comment
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Re: One slight glitch
There was recently an armature for one of these generators on eBay. The armature and splined shaft may be available as a service part, especailly from an aftermarket producer who supplies generator shops. Not sure if you could build one without the right rear flange though.Comment
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Re: One slight glitch
Yea, its twice cable speed instead of half. I think a speedo shop can recalabrate, if the bearings and head are OK.Comment
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Re: One slight glitch
If the current head can be recalibrated that would be the simplest cheapest way to go. That would be the first thing to check out.
As an alternate, there is a complete tach drive generator on eBay right now that can be bought for $350 or less. That's not too bad adeal considering it has all the brackets, etc. You would still have to buy a regulator and a wiring harness. I am assuming that these were removed when the alternator was installed.Comment
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Re: Another Glitch
The head may be calibrated but the REV counter will not be correct.Comment
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I took mine to
Corvette Specialties of Maryland (410) 795-3180. They converted my '58 tach to distributor drive and overhauled it, which made it a lot quieter. Cost was around $175, if memory serves. As Wayne says, a local speedo shop could also probably handle it. I took my speedometer to North Hollywood Clock and Speedometer. I expressed skepticism (tactfully) about whether they would have the skills and parts to do a Corvette speedo this old. The guy then walks behind a bench and pulls out a complete guage cluster from a '60 Corvette they had completely redone! Their prices were a little lower than Corvette Spcialties of MD and my speedometer certainly looks great, but alas, my car still isn't on the road, so I can't give a complete quality report for either.Comment
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