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tach question

ashman

ashman

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my '72 has the cluster with optional gauges, but no tach. I'm thinking of buying the tach conversion kit frim LMC (36-1931), but someone around here mentioned getting a tach that was compatible with HEI and it got me wondering. I'm assuming the tach is made for a stock engine.

I converted to HEI on my 350 long ago, will this tach work for me? is there a difference between points and HEI for a tach?
 
ashman said:
my '72 has the cluster with optional gauges, but no tach. I'm thinking of buying the tach conversion kit frim LMC (36-1931), but someone around here mentioned getting a tach that was compatible with HEI and it got me wondering. I'm assuming the tach is made for a stock engine.

I converted to HEI on my 350 long ago, will this tach work for me? is there a difference between points and HEI for a tach?
Click to expand...


The tach will work just fine with the HEI. I've had one in my truck with an HEI for 10 years and it has been great.
 
I have a factory tach and switched to hei as well but my tach reads high when I'm on the freeway. It reads 3500 when it should be around 2500. Seems to be fine while idling and when under 30 mph. I don't know much about tachs accept what mine does.
 
All of the threads I have come across on this subject are kinda old. Has anyone 'broken the code' on using the stock tach with HEI? Most of the places that sell the new clusters (or parts to rebuild one) specifically say - "Does not work with HEI."

I would imagine that someone is selling something which makes this work..........
 
lol, I read your response and didn't realize it was my thread. :D

I ended up going aftermarket for my tach (after switching to an LS engine) so I didn't try it myself, but I would take @bigblock72 word for it that it works.

Just guessing, but at worst you'd have to add a pull up or pull down resistor if the signal wasn't the right voltage, but otherwise, pulses are pulses. Not sure why it wouldn't work. :dunno:
 
Thank you Ashman. I've now logged major hours of Internet searches and phone calls to damn near every parts vendor around. I am dumbfounded that someone has not yet created an easy solution to this issue. Full on aftermarket panel is in the ~$1K range. Damn.

Question Ashman - how did you get a tach to fit in the narrow (depth) space between the center 'bezel' and the printed circuit board on the back of the gauge panel? Looks like it would have to be a damn shallow tach, unless you used the empty vacuum spot.......

For those facing this issue in the future, I've priced out individual gauges (If I said *#$# it and went with all aftermarket in the stock panel), ready-built aftermarket, and "new" panel/gauges - (minus) tach and add aftermarket tach, and I keep coming up with similar numbers. It's starting to look like if you have a gauge panel/cluster/wtfever that is in bad shape (and you are picky about those things, as I am), you are better off just going full on 'aftermarket' cluster. I've found (during my calls today) a few who were helpful, knowledgeable, and appear to make nice products if you are willing to drop ~a grand to get what you want.

I don't know why (who can explain their 'taste?'), but I really like the stock dash cluster in these First Gens. Simple, all business, no fancy electronics. If possible, I want to stay as close to that as I can. I'd say the closest to original I have found so far is this one: http://shop.classicinstruments.com/ct67hr-2
 
Dirsuper said:
More food for thought......I REALLY like these gauges.......https://www.summitracing.com/parts/...ewart-warner&gclid=CJ2XkYuH0NMCFQxofgodwd4Bgw

If you go to Stewart Warner's website you can get better pics, and see the clock you can add to fill the empty hole (that statement is ripe for exploitation!)........the search continues!
Click to expand...



Have you considered going to a restoration place like Redline Gauge Works?

They can fully restore factory gauges to look brand new, and repair / modify a badly calibrated tachometer to make it accurate again.

No idea what they charge, but if you want a factory look with more reliable electronics behind it I'm pretty sure that's what they can do.


-G
 
Thank you for the tip Greg. I called them today. If I send them a stock tachometer, they can make it work (correctly) with an HEI for $250.

So $639 for all new cluster (with clock) from here: http://www.truckandcarshop.com/trucks60_72/t60_040.html
+
$250 for tach 'correction'

= $899 for a fully (aside from clock) correct set with a working tach. As expensive as that is, given all of the options I have looked into (and my strong desire for a stock panel), this is looking like a decent option. Hell, just for the ease alone (given the fact that I already have my Painless wiring harness), it might just be worth it. Might be a good (insert Hallmark Holiday groan) Father's Day gift!

I am so damn thankful for this board........amazing freakin resource!
 
Dirsuper said:
Thank you for the tip Greg. I called them today. If I send them a stock tachometer, they can make it work (correctly) with an HEI for $250.

So $639 for all new cluster (with clock) from here: http://www.truckandcarshop.com/trucks60_72/t60_040.html
+
$250 for tach 'correction'

= $899 for a fully (aside from clock) correct set with a working tach. As expensive as that is, given all of the options I have looked into (and my strong desire for a stock panel), this is looking like a decent option. Hell, just for the ease alone (given the fact that I already have my Painless wiring harness), it might just be worth it. Might be a good (insert Hallmark Holiday groan) Father's Day gift!

I am so damn thankful for this board........amazing freakin resource!
Click to expand...

You can also rework your stock cluster with new gauges. It looks 99% factory and almost no one can tell it's not. I stole the idea from Greg. Just used all "sport comp" gauges since they look pretty close to stock. I gotta believe you'd be into it for a lot less than $650 of cost is a more of a driver than time.
 
@Dirsuper do you already have a stock tach? If so can you hook it up to one of your other vehicles to see if it is accurate? If it's not accurate or if it doesn't work then you can recondition it. Just seems like a hassle unless you know it's bad. Many guys seem to run stock tach on HEI just fine.

Your link above seems to be for non-hei vehicles that want a tach. Is that your situation? I thought it was that you were concerned the tach might not work with the hei you have.
 
ekajkrats, Sorry if I de-railed my own question. I am probably 'over-thinking' this (I have a tendency to do that). You might say that right now I have nothing. I have a stock gauge panel without tach. However, I want a tach when I bring it back to life. I am ready to start installing the wiring harness, but want to install the gauge cluster at the same time......which led me to the discovery of the "stock tach and HEI issue." Honestly, the more I read, the more I think it might just be bs. Sure, the tachs are not terribly accurate, but I would not expect "dead-on balls accurate" from a 1972 gauge. I was more worried about smoking the new tach.

In summary - my concern is that I buy a brand new dash cluster, hook everything up, start the engine - and BAM, I fry the new tach.
 
Dirsuper said:
In summary - my concern is that I buy a brand new dash cluster, hook everything up, start the engine - and BAM, I fry the new tach.
Click to expand...
Yeah that would suck! Well, I must say, the detail of your build is impressive and inline with thinking things through and doing them right.
 
You won't fry the tach. I have a reproduction one in my '72 C10. The reason that they say that it won't work with HEI, is the connector needs changed. It won't just plug in.
As far as accuracy, mine seems to match my timing light in the lower RPM, and I hit the MSD rev limiter slightly ahead of the tach reading. So it may be somewhat slow, but good enough for me since I have the rev limiter.
 
Sorry that I forgot to mention, mine WAS hooked to HEI, but now to MSD E-curve.
 
Took notes this weekend, and made 5-6 phone calls today. Long story short - For all of that research, I gained nothing but peace of mind. If you are using a new wiring harness (as I am), adding a filter will smooth it out/prevent bouncing, but the stock tach will work with HEI. Sorry I did not listen to those who said so initially, I am a 'bit' anal with things like this.

Funny anecdote - I found a guy who will rebuild my gauge cluster (adding tach and vacuum gauge) for $600. However, for $600 I can buy a brand new one here (http://www.truckandcarshop.com/trucks60_72/t60_040.html). Why the hell would I pay to get mine rebuilt when I can buy a brand new one for the same price?

I am going to order the new cluster and a filter (http://www.speedwaymotors.com/Classic-Instruments-SN20-Tach-Filter,5613.html) for $24 and call it done.

I appreciate everyone's input.
 
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