DIY Tach Filter Questions - Team Camaro Tech
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post #1 of 12 (permalink) Old May 22nd, 16, 09:58 AM Thread Starter
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Question DIY Tach Filter Questions

Let's begin with I am not an electronic genius, I learn as I go. My mistake was when I installed a reproduction factory tach with a Summit electronic ignition system thinking the tach would function as intended. Low and behold it did...for the first few start ups, then nothing. I spent two days researching the whys, whats and hows this might be, only to discover a tach filter is a must, otherwise you will burn up your tach!

Now my questions:

1. Why do we not have a "Tach Warning Sticky" alerting members that a filter or other device is required when installing after market ignition? Rather than telling us we just threw $250 + out the window after the fact. Within this sticky we can include the instructions on how to make the filter.

2. Jim's instructions on the filter are good but not great. Searching for the capacitor I am finding there are what seems like a "zillion" different voltages or VAC's. Jim never really says what voltage is required in his directions, therefore you can only assume. I really do not want to burn up another tach, by assuming and getting this wrong. What is the recommended voltage for the capacitor used in the filter?

Any help or assistance in this matter will be appreciated. Thank you.

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post #2 of 12 (permalink) Old May 22nd, 16, 01:27 PM
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Re: DIY Tach Filter Questions

Rick - Every HEI module has a warning that they will damage old style analogue tachometers or at least, notes that they do not support them and almost all manufactures offer pre-made filters for old analogue tachometers. Some have to be matched to the ignition module others are more generic.

That said and your admittance that electrical is not your strong suit maybe making your own adapter is not the right solution.DIY Tachometer Filter Jim's instruction list for the parts required including the 270 ohm, 1/2 watt resister. https://www.radioshack.com/products/...-resistor-pk-5 is bare bones but so is the filter he came up with. It is a simple easy to make and no frills. You can send him a message if you have difficulty or contact him at his site Camaro forum FirstGens.com


Having us post a warning here at Team Camaro is a bit like locking the barn door after the horses have run away.

just saying.

All the reproduction first generation tachometers including OER for Camaro's I have seen are all marked not for HEI systems, and most catalogues and websites that sell them also state they are not for use with HEI systems. But all is not lost if you already have it installed on a HEI system. For others reviewing this thread with a new in the box OER and or STILL working but flaky, jumpy, or incorrect original tachometer and new HEI system, unplug the tachometer NOW and take a look at purchasing one of these smart modules. This TachMatch module sounds like a universal translator:
TechnoVersions - Home of TachMatch, MeterMatch and MotorMatch Useful for those folks who have just done an engine swap.


But is sounds like the best solution for you Rick is to just buy a replacement circuit board for your blown OER tachometer:
Greg sells this one: Team Camaro Classifieds - All Years - 69-77 tachometer circuit board - NEW!
And can customize it for you.

Or Randy C's Tachometer shop can replace the circuit board in your tach with a newer style board that will work correctly. Services - RC Tach Shop
You can reach him at (812) 989.4727 (812) 284.2555. Randy - rctach@gmail.com

Either of these guys can get you a working HEI style replacement board for the OER tachometer and it sounds like the cheapest solution as it will revive the tachometer you have already killed so you save the replacement costs.


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Last edited by 69-Pace; Sep 18th, 16 at 02:03 PM.
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post #3 of 12 (permalink) Old May 22nd, 16, 01:39 PM
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Re: DIY Tach Filter Questions

Quote:
Originally Posted by Legacy 69 View Post
Let's begin with I am not an electronic genius, I learn as I go. My mistake was when I installed a reproduction factory tach with a Summit electronic ignition system thinking the tach would function as intended. Low and behold it did...for the first few start ups, then nothing. I spent two days researching the whys, whats and hows this might be, only to discover a tach filter is a must, otherwise you will burn up your tach!

Now my questions:

1. Why do we not have a "Tach Warning Sticky" alerting members that a filter or other device is required when installing after market ignition? Rather than telling us we just threw $250 + out the window after the fact. Within this sticky we can include the instructions on how to make the filter.

2. Jim's instructions on the filter are good but not great. Searching for the capacitor I am finding there are what seems like a "zillion" different voltages or VAC's. Jim never really says what voltage is required in his directions, therefore you can only assume. I really do not want to burn up another tach, by assuming and getting this wrong. What is the recommended voltage for the capacitor used in the filter?

Any help or assistance in this matter will be appreciated. Thank you.
Want the best way to do it? Brian hit the nail on the head. Skip the tach filter. Unless you are working with an authentic GM tach, it aint worth the time or effort as the filters don't work with OER tachs. MSD sent me filter after filter to work with their HEI module and coil and nothing worked. Tried to make my own, nothing. Eventually fried the tach. Send you're non GM tach to Redline Gage or similar outfit. They'll fit the guts of a modern Stewart tach mechanism behind your tach face and needle. Well worth it.

69 SS clone, fathom green, TMI sport seats, 200r4, 3.42 posi rear end, IROC steering box, SPC control arms, koni shocks.. Future mods include bolting on the Profiler heads, FIRST TPI, and roller cam sitting in the garage
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post #4 of 12 (permalink) Old May 22nd, 16, 03:09 PM
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Re: DIY Tach Filter Questions

Rick,
Contrary to Brian's comment regarding all 1st gen reproductions marked not for HEI, here is one tach that will work with factory GM HEI. I know, I have one and it worked right out of the box...no filter needed. Scroll to the bottom and read the claim! Just sayin...
1969 Chevrolet Camaro SS350 Dash Tachometer Tach 5000 RPM | eBay

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post #5 of 12 (permalink) Old May 22nd, 16, 06:52 PM
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Re: DIY Tach Filter Questions

Karl - The devil is in the details....Should we assume you have installed a GM HEI distributor?

The disclaimer says on the ebay page
Quote:
This tach will work with factory GM points or factory HEI. It may need a tach adapter when using this on MSD or after market ignition.
And on their real website it is a bit more clear
Quote:
Interior - IN-DASH TACHS: FACTORY STYLE TACH INSTALLS IN DASH. WILL WORK WITH FACTORY POINTS IGNITION OR GENERAL MOTORS FACTORY HEI. ANY AFTERMARKET IGNITION SYSTEM MAY REQUIRE AN ADAPTER OF SOME KIND. PLEASE CONTACT THE VENDOR YOU PURCHASED YOUR AFTERMARKET IGNITION SYSTEM FROM TO SEE IF AN ADAPTER IS NEEDED.
There was no factory HEI in 69, however there was limited TI in 69 Camaro Transistor Ignition Systems but GM factory tachometers did not work with it, but Chevrolet racing expected folks would be using an mechanical tachometer on the track, so nothing was done to filter it so it would work. The documents say if the aftermarket tachometer had its own power feed it might work. SW had an adapter for its tachs on Chevy TI systems. So unless you have installed a full 74 HEI dizzy it will not work according to them.


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post #6 of 12 (permalink) Old May 22nd, 16, 07:16 PM
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Re: DIY Tach Filter Questions

Quote:
Originally Posted by 69-Pace View Post
Karl - The devil is in the details....Should we assume you have installed a GM HEI distributor?

The disclaimer says on the ebay page
And on their real website it is a bit more clear

There was no factory HEI in 69, however there was limited TI in 69 Camaro Transistor Ignition Systems but GM factory tachometers did not work with it, but Chevrolet racing expected folks would be using an mechanical tachometer on the track, so nothing was done to filter it so it would work. The documents say if the aftermarket tachometer had its own power feed it might work. SW had an adapter for its tachs on Chevy TI systems. So unless you have installed a full 74 HEI dizzy it will not work according to them.
I do have an Official GM HEI dizzy installed...I understand what you meant in your original comment, however, I thought the explanation might be a little vague for someone like myself who has changed to HEI with expectations of obtaining a factory looking tach that would really function with an HEI dizzy without using a filter. There are those of us who obviously aren't concerned with originality, but perhaps wanting a period looking tach and overlooking the HEI dizzy, of course. Just a personal thing for me and wanted to offer my experience to others. No offense intended.

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post #7 of 12 (permalink) Old May 22nd, 16, 07:38 PM
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Re: DIY Tach Filter Questions

None taken, just didn't want anyone to rush out and buy one and then find it wouldn't work then cry foul at you.

When all is said and done having the circuit board replaced with one that can accept any HEI - GM or aftermarket is a small price to pay for an original looking and working tachometer in residence in the dash carrier.


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post #8 of 12 (permalink) Old May 22nd, 16, 07:45 PM
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Re: DIY Tach Filter Questions

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Originally Posted by 69-Pace View Post
None taken, just didn't want anyone to rush out and buy one and then find it wouldn't work then cry foul at you.

When all is said and done having the circuit board replaced with one that can accept any HEI - GM or aftermarket is a small price to pay for an original looking and working tachometer in residence in the dash carrier.
Good point Brian...caveat emptor comes to mind. It is up to the buyer to do the homework...without it, they're doomed to failure.
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post #9 of 12 (permalink) Old May 23rd, 16, 09:13 AM Thread Starter
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Re: DIY Tach Filter Questions

Great replies, thank you to all for taking the time to respond.

Brian I noticed you are a moderator at the site, therefore you have the power to keep the future horses in the barn, so to speak. A simple warning sticky that encompasses this thread, the HEI warning threads as well as Jim's filter thread will help us builders who do normally take the time to read before. Please note, my Summit ignition pack booklet only mentions installing a filter in the Troubleshooting area, again too late to save.

That being said, I like the idea of installing Greg's circuit board, this would have to be of my own doing though. I will definitely contact Greg to confirm weather or not this is a DIY task. You see living in Canada adds a whole other twist with 30% on the dollar, shipping the tach to Louisiana, having a circuit board installed, return shipping, customs fees, taxes etc would pretty much buy a new tach.
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post #10 of 12 (permalink) Old May 23rd, 16, 11:01 AM
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Re: DIY Tach Filter Questions

It is not too hard to crack open the tachometer and replace it. Don't know if Greg has decent instructions, but when in doubt take tons of detailed photos and notes so you can put her back together. Or you can call or email Randy for assistance on best route for you to take.
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post #11 of 12 (permalink) Old May 24th, 16, 04:21 PM Thread Starter
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Re: DIY Tach Filter Questions

Brian, excellent advice I'll do just that, thank you for the connections.

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post #12 of 12 (permalink) Old May 24th, 16, 05:22 PM
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Re: DIY Tach Filter Questions

No problem Rick. Let us know how it works out for you.


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