My tach jumps a little between 1500-2000 rpm. I might get a 200 or so RPM bounce/jump. Been like that for a while, I'm just getting around to troubleshooting it. I'm assuming it's either a bad wire, crack in the cap or something related to the ignition parts.

For what it's worth, I got the car with the current plug wires and everything already set up. It's a 70 with HEI, big block. Had all the plugs out a few weeks ago and they looked perfectly normal and had good color.

Ideas?

RMX

Your speedo cable could be drying out. Might be time to re-lube it.

Your speedo cable could be drying out. Might be time to re-lube it.

Tach not the speedo. On that note, I notice it at standstill if I increase the rpms to 1500 or so.

RMX

I assume this the factory tach? My 78 had an autometer tach and it did the same thing with the HEI in it. It would idle and then kick slightly. I don't recall it doing it at higher rpm. It seemed to clear up at that point.

Tach not the speedo. On that note, I notice it at standstill if I increase the rpms to 1500 or so.

RMX


I lose for reading comprehension! Sorry :(

Pretty normal idle characteristic. I wouldn't be concerned.

I assume this the factory tach? My 78 had an autometer tach and it did the same thing with the HEI in it. It would idle and then kick slightly. I don't recall it doing it at higher rpm. It seemed to clear up at that point.

No, it's an aftermarket tach.

Engine sounds fine...just going to let it be.

RMX

Assuming it has good connections, you may want to investigate the tach filters that MSD sells.

I went through a lot of trouble years ago to get my stock 5.0 tach to work with a Jacobs ignition unit. They said buy a couple and see what works, and I guessed right the first time.

I notice that MSD also sells them. Call and ask about your brand of tach.

I just put a cheapie Suntach II in my 66, plugged it into the HEI terminal and it works fine

I chased grounds and everything else I could think of at the time. Never installed the filter though.

Pretty normal idle characteristic. I wouldn't be concerned.

X2.:yes:

Check the electrical forum. There's a thread there on the same topic. You can get a tach filter for use with an HEI distributor.