Dancing tach at speed and acceleration

[TheBirdistheWord]

4wire tach and matchbox dizzy

Starts just over 2krpm, and doesn't seem to affect engine performance. (I.e. engine doesn't seem to be misfiring) But it bugs the living bajeesus out of me.  I speculate if it's an ignition issue it may be robbing me of some power and I just can't tell? There doesn't seem to be any consistency when it happens either. Shows up and goes away while weather is cold/wet/moderate/hot as well as engine cold/hot

Edited May 19, 2020 by TheBirdistheWord

[john510]

The end might be near for that tach.Mine did the same thing for quite some time,then just quit working.I checked every connection there was and found nothing.Bought another factory tach when they were still affordable and it works fine.

[datzenmike]

 Does it do it sitting and slowly revving it up above 2K? Check for loose wire on coil or to distributor. If you installed this tach check those connections also.

[Draker]

Mine does this with a speedhut tach. I thought it was noise on the signal line. Installed a tach noise filter. Still was the same. Replaced dizzy, it got a lot better but still does it occasionally.I bet it’s your dizzy. It’s probably worn out. 

[datzenmike]

By revving slowly in neutral you may avoid vibrations that might affect a loose connection. If it only does it while driving then probably a loose wire.

[TheBirdistheWord]

14 hours ago, datzenmike said:

 Does it do it sitting and slowly revving it up above 2K? Check for loose wire on coil or to distributor. If you installed this tach check those connections also.

Occasionally it will happen while sitting, and slowly up to 2k. Copy that

40 minutes ago, datzenmike said:

By revving slowly in neutral you may avoid vibrations that might affect a loose connection. If it only does it while driving then probably a loose wire.

It happens in neutral as well but only higher rpm

 

 

6 hours ago, Draker said:

Mine does this with a speedhut tach. I thought it was noise on the signal line. Installed a tach noise filter. Still was the same. Replaced dizzy, it got a lot better but still does it occasionally.I bet it’s your dizzy. It’s probably worn out. 

Is there a source for rebuild parts for matchbox dizzy? 

[datzenmike]

49 minutes ago, TheBirdistheWord said:

Occasionally it will happen while sitting, and slowly up to 2k. Copy that

It happens in neutral as well but only higher rpm

 

 

Is there a source for rebuild parts for matchbox dizzy? 

 

The EI module is solid state electronics, no moving parts. It can't do it occasionally or part time. It can't know if you are driving under load or just revving it. I would definitely look at tightening any connections including a good ground. None of this costs anything to check and tighten. The module from Nissan is $196.00 so maybe half that from NAPA and probably half that again for some piece of shit from China. Alternatively the HEI module from a GM can easily be wired in but if it is a loose connection all this is for nothing.

[Draker]

11 hours ago, TheBirdistheWord said:

Occasionally it will happen while sitting, and slowly up to 2k. Copy that

It happens in neutral as well but only higher rpm

 

 

Is there a source for rebuild parts for matchbox dizzy? 

@distributorguy probably has a source. He does it professionally. He’ll even recurve it correctly for the application. 
 

 

[TheBirdistheWord]

On 5/20/2020 at 10:40 AM, datzenmike said:

 

The EI module is solid state electronics, no moving parts. It can't do it occasionally or part time. It can't know if you are driving under load or just revving it. I would definitely look at tightening any connections including a good ground. None of this costs anything to check and tighten. The module from Nissan is $196.00 so maybe half that from NAPA and probably half that again for some piece of shit from China. Alternatively the HEI module from a GM can easily be wired in but if it is a loose connection all this is for nothing.

Looks like it was just loose-ish connections. Everything except the tach had some wiggle to it.  Gave the spade connectors the needle nose treatment and tach movement is solid as a rock!  Also, i was actually referring to the mechanical parts in the dizzy. I have two spare EI boxes if I need them. 

18 hours ago, Draker said:

@distributorguy probably has a source. He does it professionally. He’ll even recurve it correctly for the application. 
 

 

Thanks! I'll look into this for the spare matchbox body I have laying around. 

[datzenmike]

On the EI distributors there is just a spinning shaft with a reluctor. Almost no load on them. Points have a strong spring the shaft has to pry against to open the points.

 

Well... that was a cheap fix.