[OCMDGTO]

69 GTO with stock tach and their HEI dist. My tach is way off intermittently reading normal or way high. Anybody else having this problem and how did you fix it? Tach adapter?

[Formulajones]

That was an issue when this stuff first came out and I had asked about it a couple times since, never got a clear answer which led me to believe it was still an issue.
Thought it was an oddity because all my factory tachs work with msd and the like but progression is a problem??

I haven't heard of a solution yet, hopefully you get one.

[68 Firebird]

So far no issues with my hood tach.
Been using the PI HEI for a few months.

Gerry

[Motorcycle79]

My 79 I noticed is off as well it seems close at low rpm but off around 500 or so at high rpm’s.

[steve25]

Is your distributor case grounded well to the block thru the bolt and hold down clam?

Make a resistance check to confirm.

[OCMDGTO]

Thanks for the responses. Distributor ground should be good, the tach worked well as I recall with my DUI HEI. Grivera on here reduced signal from Distributor to tach from 12v to 5 but he has Dakota guages not stock ones.

[Verdoro 68]

I initially ran my hood tach of the coil but switched it over to the tach lead off the distributor. No issues other than sometimes I'll fire up the car and it takes a minute for the tach to start working.

[73ta]

My tach was off quite a bit, 500 rpm at higher rpm's. Got a new upgraded tach board that has a calibration potentiometer on it. Much better now. Tach board guy said factory is + or - 10% on accuracy. With the new board you can adjust it to get it much closer.

[JLMounce]

Originally Posted by 73ta

My tach was off quite a bit, 500 rpm at higher rpm's. Got a new upgraded tach board that has a calibration potentiometer on it. Much better now. Tach board guy said factory is + or - 10% on accuracy. With the new board you can adjust it to get it much closer.

Link to the tach board?

[Singleton]

I use two of the PI distributors, both are the small cap versions with external factory type coils, so the factory tach wire connects to the neg side of coil. No issues.
I have no experience with their hei versions, but the instructions show two ways to connect the tach. Which one are you using?

[73ta]

Originally Posted by JLMounce

Link to the tach board?

https://www.cajuntachshop.com/

https://www.ebay.com/itm/30458915696...Bk9SR9DptsWzZw

I bought the ebay one for my 73 TA that I believe ebay seller sources from Cajuntachshop.

[JLMounce]

Got it, thanks. This doesn't look like it's for hood tachs. is that accurate?

[OCMDGTO]

Originally Posted by Singleton

I use two of the PI distributors, both are the small cap versions with external factory type coils, so the factory tach wire connects to the neg side of coil. No issues.
I have no experience with their hei versions, but the instructions show two ways to connect the tach. Which one are you using?

It's coming off the cap, I wasn't aware there was 2 ways to set it up. I need to look into this, thanks.

[73ta]

Originally Posted by JLMounce

Got it, thanks. This doesn't look like it's for hood tachs. is that accurate?

Give them a call. IDK. They might be able to modify your stock board.

[65madgoat]

I'd highly suggest to avoid the Cajun Tach Shop.



Buy a circuit board part only from WEST COAST AUTO PARTS (not applicable to hood tachs)

[73ta]

[QUOTE=65madgoat;6612642]I'd highly suggest to avoid the Cajun Tach Shop.


Why? Tell us more!

[65madgoat]

Bad customer service, major delays when shipping, and most importantly parts are inferior to West Coast Auto Parts.

Try and get a hold of Cajun Tach and get back to me. Good luck!

Call West Coast and someone will answer and help you asap - and likely let you know how much they deal with unsatisfied Cajun Tach customers too.

[OCMDGTO]

I'm still trying to figure this out. What I've learned is the MSD tach adapter didn't help. The PI Pontiac HEI does not have the additional tach lead at the bottom of the cap so I'm still running off of cool negative at the usual HEI location. Been back and forth a bunch with Pete Serio and PI.

[68 Firebird]

This is odd. Using PI HEI for a few months and had no tach issues.
Using GM HEI for years and then went PI.
My tach is a NOS replacement as original was bad.
Used same tach connection on both HEI’s.

Gerry.

[Region Warrior]

From memory on 67 fb positive lead was to fuse block ignition switch.
Negative to - on coil?
Gm hei has positive tack terminal. Made a separate ground lead.
I think...was back 79...