Factory Tach and HEI Distributor

[Already Gone]

I've heard some comments about factory tach dashes and HEI s.. From what I've gathered I'm asking do the factory tachs not work properly with a HEI Distributor? If that is the case is there something you can do so the factory tach will work. I've been driving my all original 69 CST around want to keep doing that but would like the reliability of a HEI or Mallory Streetfire Distributor like I have in my other truck. I just love my 3 on the tree !!

[too much stuff]

I am running factory tachs with stock HEIs in 2 trucks and no problems here.

[PHAT TONY]

I gotta stock tach and HEI ignition, works fine.

[chipflyer]

Do a google search for "tach filter". You will find that they sell the original GM filters on ebay or you can find other aftermarket filters. They were originally used on gm cars in the 70's and 80's that had factory tachs and HEI ignition. Add one of those and you may find it works better. Mine works ok too without one but our tachs were originally designed to work with points distributors/coils and the tach output pulse is different, that's why the cars and trucks after 73 had the factory tach filters installed. Lots of people claim the needle bounce will stop if you experience that and add the filter.

Jeff

[too much stuff]

Originally Posted by chipflyer

Do a google search for "tach filter". You will find that they sell the original GM filters on ebay or you can find other aftermarket filters. They were originally used on gm cars in the 70's and 80's that had factory tachs and HEI ignition. Add one of those and you may find it works better.

Jeff

Wasn't that mainly for radio noise?

[VA72C10]

It's more of a concern with aftermarket tachs and HEI...there are some mfr's that won't honor a warranty on an aftermarket tach because HEI has been known to fry them (have seen it posted on here by several) However, I also know many people using both factory and aftermarket tachs with no issues whatsoever and some dealers of the aftermarket tachs have no disclaimers...

[chipflyer]

No, its to clean up the pulse from the signal. Wouldn't you know I can't find it now but I saw an article some time ago that talked about how the signal can be jacked up and GM knew they could add the filter to cheaply and easily make the tachs operate better and be more accurate. If you take a look over on the corvette forum or on Nasty Z28 you will find that many people have added them and claim it makes a difference. As I said, my tach works but I know that the higher the rpm the more inaccurate it gets. Been meaning to add one to see if it helped but have never got around to it, not that big a deal.

Jeff

[too much stuff]

Originally Posted by chipflyer

No, its to clean up the pulse from the signal. Wouldn't you know I can't find it now but I saw an article some time ago that talked about how the signal can be jacked up and GM knew they could add the filter to cheaply and easily make the tachs operate better and be more accurate. If you take a look over on the corvette forum or on Nasty Z28 you will find that many people have added them and claim it makes a difference. As I said, my tach works but I know that the higher the rpm the more inaccurate it gets. Been meaning to add one to see if it helped but have never got around to it, not that big a deal.

Jeff

Good to know, jeff. Not even sure how accurate these were when new...

[chipflyer]

I Agree Eric, they probably weren't that accurate, but I'm to young to remember!
Below is a pretty interesting link to a thread over on Colorado K5, seems someone from here years ago had a right up about the subject. I have the same problem as greg72 had. As my rpm's go up the factory tach reads higher than it should, a filter may help. I need to get one and try it.

http://coloradok5.com/forums/archive...p/t-34175.html

Jeff

[Already Gone]

Thanks for all the help guys. With my little 307 2bbl I'm not going to worry about high revs , so I guess its a Mallory Streetfire going in the truck.

[chewychevy67]

I dont mean to hijack but has anyone used a factory tach and added k66 transistor ignition? I am adding this to my truck to be kind of era correct but have heard they aren't too accurate with stock tachs.
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[SSBurban]

Seems to me that you can get an HEI either with or without a tach drive. Was an option when I bought mine from Summit last year. I guess I wold make sure that it has it before you buy. Somebody correct me if I am wrong here..

[hgs_notes]

I put that skip white dizzy in my truck and it works great. Had problems with the older original dizzy that a bunch of new parts never corrected. Spent less for the new dizzy than I did on replacement parts for the old one.

Oh and I run a reproduction tach of this HEI with no issues.

[Andy4639]

I run a junkyard HEI since 1989 with only one module change so far. All the HEI's I have seen have the electric Tach connection on them. Only the big block corvettes had the cable drive on them if I remember right. The Big chevy trucks like Dumps and tractor trailer ones had a cable drive tach also. I almost bought one once.

[sanford66]

Stock tach in my truck with an HEI, works fine. Joseph

[Already Gone]

I am going to call and order one tomorrow morning and hopefully they can get it to California by next Saturday. That will save me a few bucks as opposed to shipping it home.

[special-K]

That distributor may just work fine. But,I learned a long time ago that the black caps are junk and I've always gone with the tan,blue,or red caps that are made of a denser material. It may be that now there are black caps made of good material,but it was always the sign of a cheap part back in the day.

I think aftermarket tach makers use the no filter voids warranty as an escape from replacing a poor quality part. I had a next to new '72 with tach (and points) and it was smooth and accurate. They may get inaccurate with age,but they were originally accurate,just like all the other tachs.

[RichardJ]

This doesn't apply directly to using a '67-72 tach with an HEI, but it is the filter Chevy used with the HEI. I have found them on '80s cars with big HEI's and small V6 HEI's with tachs.
They look like standard radio noise suppression caps except they have a wire coming out of both ends.
I thought you might like to see this.

[502ms]

I'm running Autometer gauges, truck was not originally equipped with a tach. I have the sport comp 2, running direct to the stock HEI
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[Already Gone]

I orderd my HEI from Skip white today. Its gotta be better than points and condenser. The 69 has been starting instantly with one pump of the gas pedal and this morning it was cold when I finished work and it didn't want to start. I'm thinking its the points that kept it from starting.

[special-K]

Points have always been reliable for me. There was never anything wrong with them. Electronic ignition was just a maintenance-free upgrade,but also a much higher spark. But,points never left me stranded and electronic has. If something's wrong,you have nothing.
The factory tachs are the same as all tachs put in GM cars. They are accurate when in proper working order. The purpose of the filter is to steady the reading,the same as the resistor on a fuel gauge.

[Already Gone]

I had the Skip White HEI installed in my 69 with factory tach and the truck and tach both work fine.
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