Hi,

The hood tachometer on our 350 -4bbl has a slight problem every so often. Between 1500 and 2000 rpms the needle will flutter for a few seconds then calm down. Can someone tell me is this something that be fix or is it a common glitch that just happens.

Thanks in advance
Sam

Never seen this but I have seen needles do strange things when the power for the tach is combined with other options power leads. When you power up another option the needle goes haywire. If your tach was added and isn't wired from the factory you could try running a separate power lead to the battery for a test.

If you have the guts to take it off (it's pretty easy) unscrew the 4 screws, and then it's proberbly just old grime that's sitting just under the needle(in the bottom - not touching the needle but around the small windings), -clean it, and you're good to go.

What are you running as an ignition system?

Here's a neat thing that happened with my tach yesterday.... When I went to start the car the battery was a little low. So I used my jumper box to start it. I'm sure the battery was low on volts. My tach was at 5000 rpm at an idle. When I revved the engine it went down to 2000 rpm. It was working exactly backwards with 6000 as a zero. After I drove around a while the battery must have regained it's charge because the tach started working normal again. Strange things these tachs......

that was because you were in reverse . .. -put it in drive, and then tach will work again...


maybe..

No wonder my hat kept wanting to fly off! Which reminds me of a redneck joke.... You might be a redneck if your car goes faster in reverse than drive..... Don't stick your head out the window or you will get a rubber beard(reverse burnout).

Or a hairy back.....

Are these old tachs supposed to work with Pertronix ignition? My $175 mint ebay "special" still is not working...black/pink to coil, black to ground...right?

When I had my distributor set up initially, I had to swap the points back in to trigger the early '60s era Allen distributor machine. It did not sense the Pertronix trigger. New tachs work fine with them, but I don't know why some of the old ones don't. My tuneup tools work fine with the Pertronix, and they are '70s era.

From what I've seen, it's hit and miss with tachs (new and old) working with after market ignitions. The fix is typically a $20 tach adapter from MSD or one of the others.

I bought a tach adapter but didn't need it (and returned it). My original '67 tach works just fine with my EFI distributor and MSD 6A box. Go figure?

Well that explains my problem I hope. I just looked at them and it appears there are a lot of different ones, what do I specify or John, do you recall which one you had? I assume they are a transformer of sorts??

This is the one most people try: http://store.summitracing.com/partdetail.asp?autofilter=1&part=MSD%2D8910&N=700+115&autoview=sku

Thanks John - I assume this works with Pertronix as well....

I can't say what it does and doesn't work with. Did you search the PY site for an answer to your problem?

No I did not but will try it. (if I can remember my login names)

Did not find much on the PY site, my tach just sort of vibrates between 0-250 rpm. Will post there as soon as I recall my password there!

Does that sound like a tach adapter fix?

Not necessarily by my own past experiences, but I did have to run a tach adapter with my 6AL box added to my point type distributor, then had to use a different adapter when I dropped in the MSD distributor. Thats why I was curious about your ignition system.

Pertronix (not the Pertronix II) system with their "Flamethrower" coil. That's it. Sorry Greg, thought I had mentioned that, but my memory is good, albeit short!

I haven't seen "Sam" since he posted the original question. Have you?

The Hood Tach is pretty simple caveman stuff. Really. Even one such as I figured out its simple wiring after a few years of ignorance.

It either works correctly or it does not work. Theres no intermittent area for this particular part. There are subtle differences between wiring of original ignition versus HEI, but even that is a caveman thought process. Yes, lets all use the Caveman thing, since some TV station is making a show of it this Fall.

My pertronix is all internal to the distributor, yes Nash I agree the basic wiring is pretty neandrathal stuff, but I did get some insight in the possible need for a tach adapter (pass the brontasaurus rib will ya)...so it appears even cave men can advance some...

You are right Dave, there have been many posts here about certain aftermarket HEI systems and componments that might require a filter/adapter. I owe you a Bronto Burger and a side dish of Teredachto wings.

...I'll bring the Neandrathal Lite Beer

Yaba daba do!

Has this been a problem since you originally hooked up your tach, or did it just start happening? First thing to check is your connections. As stated, you don't need to be a rocket scientist to figure these things out and you should also start with basic troubleshooting before throwing parts at it.

No, I purchased the tach off Ebay, an absolutely mint survivor, in storage for some time by the looks of it. I pulled off the cover and the internals look great. My car was fired for the first time a month or so ago and it has never done anything but vibrate around 0 RPM. Connnections are solid, I may just go over to my neighbors who has a 70 chevelle with points and test it on his....?