tachometer problem,,,,,,,,,,,,

[olskool]

i have a question maybe somebody can help me with. i have a 1986 monte carlo ss, it has a built 283 engine. the tach is a good bit off. it is showing about twice as high as it is really revving. it is hooked up to the distributor correctly, i think. any help will be appreciated, i have been a professional transmission rebuilder for 45 years. retired now. i have answered several questions on this forum for people although i a new here. if i can help with any transmission problem let me know. i have a vast knowledge with all, matters not the make. maybe i can be of assistance to you also.

thanks mike,,,,,,,,,,,,,,,

 

[ELCAM]

Factory tach or aftermarket tach?

 

[565bbchevy]

Which distributor? You should be running a non CCC HEI in that.
I am curious what a built small CI engine like that makes for power?

 

[CopperNick]

If you are running the factory tach, is the tach filter hooked into the circuit?



Nick

 

[olskool]

it is a factory tach, i did not know about a tach filter. what exactly does that do? calibrates the tach? i am running a factory HEI distributor. if it needs the filter and doesn't have it then that is most likely my problem!

 

[Ugly1]

Did you ever get it figured out?

 

[olskool]

no i haven't looked at it again. but if it supposed to have a tach filter and doesn't then i a sure that is the problem. it appears that somebody did a frame off restoration on this car and nay have not put it back right. i have already had to fix and hook up a few undone things,,,,,,,,,,,,,,,

 

[69hurstolds]

The tach filter, which is essentially a capacitor, only takes out electrical noises and smooths out the tach pulses. I don't think it will make your reading high all the time. But I'm not a wire biter, so electricians may know.

I believe you will need a 200-220K ohm resistor (super cheap just about anywhere). Based on some of the tach issues I've read about with Malibu and Montes. Cutlass doesn't use a filter or all these fancy resistor thingies. They have a little V6 and V8 "plug" that usually loosens and falls out at some point. The later Olds tachs got fixed with a soldered bridge wire, which was the street fix everyone was doing to the earlier ones anyway.

Anyway, these threads may help you figure some things out. Don't know what could be your problem, but good info here.

fix your stock tachometer

i tested a good unmolested stock tach and at 3,000 rpm it was off by 250-300 revolutions. at the same speed & doing the mod below tach was now off by 80-100 revolutions. at idle you cannot tell much of a difference, but u will start to notice it as the rpm increases. not 100% accur...

www.montecarloss.com

Tach filter/erratic/unresponsive/etc.

Below is the original post, but I'm hoping this will be a thread to help correct an erratic/inaccurate/unresponsive tach. From everything I've read it's a resistance value on a resistor 'pack' on the board for the tach that goes out of spec (small, white ceramic piece that looks like an IC...

maliburacing.com

90-92 Tachometer fix.... - Third Generation F-Body Message Boards

Electronics - 90-92 Tachometer fix.... - As many of you guys know... barely anyone has a 90-92 gauge cluster with a tachometer that reads properly. They almost always read too high. There has been a multitude of posts regarding finding a solution or a fix for this, but to my knowledge, no...

www.thirdgen.org

But- If you find you want/need a new tach filter...

78-88 Tachometer Filter | Dixie Restoration Depot

www.dixierestorationdepot.com

 

[airboatgreg]

The tach filter, which is essentially a capacitor, only takes out electrical noises and smooths out the tach pulses. I don't think it will make your reading high all the time. But I'm not a wire biter, so electricians may know.

I believe you will need a 200-220K ohm resistor (super cheap just about anywhere). Based on some of the tach issues I've read about with Malibu and Montes. Cutlass doesn't use a filter or all these fancy resistor thingies. They have a little V6 and V8 "plug" that usually loosens and falls out at some point. The later Olds tachs got fixed with a soldered bridge wire, which was the street fix everyone was doing to the earlier ones anyway.

Anyway, these threads may help you figure some things out. Don't know what could be your problem, but good info here.

fix your stock tachometer

i tested a good unmolested stock tach and at 3,000 rpm it was off by 250-300 revolutions. at the same speed & doing the mod below tach was now off by 80-100 revolutions. at idle you cannot tell much of a difference, but u will start to notice it as the rpm increases. not 100% accur...

www.montecarloss.com

Tach filter/erratic/unresponsive/etc.

Below is the original post, but I'm hoping this will be a thread to help correct an erratic/inaccurate/unresponsive tach. From everything I've read it's a resistance value on a resistor 'pack' on the board for the tach that goes out of spec (small, white ceramic piece that looks like an IC...

maliburacing.com

90-92 Tachometer fix.... - Third Generation F-Body Message Boards

Electronics - 90-92 Tachometer fix.... - As many of you guys know... barely anyone has a 90-92 gauge cluster with a tachometer that reads properly. They almost always read too high. There has been a multitude of posts regarding finding a solution or a fix for this, but to my knowledge, no...

www.thirdgen.org

But- If you find you want/need a new tach filter...

78-88 Tachometer Filter | Dixie Restoration Depot

www.dixierestorationdepot.com

Well put

 

[airboatgreg]

If the engine runs well, I would first hook up another tach to see if it is accurate. If so, I am thinking a bad factory tach