good morning thanks for the support this forum offers. I live in the country, only one young mechanic and he hasn't been able to help, so far.....

Last fall my car began running rough. it would start ok, but wasn't right, a definite rough idle and run. To me it felt like i had a bad plug or wire. Took the car to the mechanic and we started the car in the morning so we could see if all the cylinders came up to temperature OK - all was good there
He turned to the distributor to do a check, his investigation found small pieces of loose metal near the points, originally he was confused as to where the bits could come from, then later we talked about how the tachometer stopped working at the same time, this lead to the guess that the cable has snapped and released pieces into the points. (this is a guess)
His suggestion is that i order the new tachometer cable, and change the points over to an electronic system.
I need to check with this forum on this recommendation.
at this moment im thinking i should disconnect the tach cable, inspect the distributor area put it back together to see if the problem persists?

questions
does it make sense that the bits come from the tach cable?
could this cause the rough run?
should i change to electronic ignition? (this is a driver)
could the metal bits damaged anything else i need to be careful for?

i would appreciate the feedback, i live too far away from a municipal center (highway) to really drive it to a mechanic. i can rent a trailer if required, but hope to fix myself

with thanks.......reg

 

There is no way broken tach cable pieces can migrate up to the points.
Did the mechanic disconnect the tach cable and remove the large brass fitting that the cable connects to and screws into the distributor housing?
There is a gear inside that can wear out and is driven by the distributor main shaft.
You need an old mechanic who is familiar with older Corvettes.
There is no reason why you should switch to electronic.

 

I would find a new mechanic and only fix what’s broken and not just throw parts at it hoping it will fix your problem

 

Reg,

My feeling is that nothing from the tach cable has found there way up to the breaker plate that holds the points. I would look at the moving parts in that area carefully for rubbing etc., don't forget the distributor cap.

Put a new set of points/condenser in and get the car to run normal before you change any stock engineering.

 

as no old school mechanic is available here, should i pull the distributor assembly and take it to a mechanic in a local community? Im sure i can find one on my daughters community about 3 hours away

 

No need to pull the distributor. Just replace the points or just check the dwel and adjust. Where are you located someone might be able to point you to some great help

 

Reggie, you need to post where you are located, someone here may be close enough to help you. I also live in a very rural area and wouldn't post anything too specific to where I live.

 

If it were mine I would not pull the distributor, just inspect and do a tune up in the car, put a little bit of fresh gasoline in also.

If you are not a skilled hand, look for someone to help you and do some google on chevrolet points install. It's something you can do yourself if you take your time.

 

i will do that. i have reached out to the local car club (hour away) to see if they can recommend someone to come out after new parts are in, thanks,,,,,,,reg

 

i live in the east kootenays located in BC canada

 

If you don’t have a dwel meter you might not make it any better. You can set the points with a feeler gauge and get it close but to do it right you should have the right tool.

 

Agree with avoid parts-swapping and identify the problem. First, what engine is in your car? What tranny?

First: What did the small bits of metal look like? Head of a pin size, BB size, or pea-sized? Were they magnetic and did you find any possible sources under the dizzy cap?

How did everything else look under the cap? Points okay and condenser and all wiring intact? Cam lobes look okay? Does the breaker plate move smoothly and do the mechanical advance cams work properly and smoothly?

There is no path for any parts from the tach drive to get under the cap. The clearance between the dizzy shaft and upper bushing is measured in the single thousands of an inch (.002-.007 is normal, IIRC), therefore no pieces from the tach cable can get there.

There are several reasons that your tach may not be working, including the cable, but also the tach drive gear in the dizzy, as well as the dash instrument itself. It wasn't clear, did the tach quit the same exact time that the car began running poorly?

When you say "running poorly" please explain more, for example:

Does it cold start and hot start quickly or does it require a lot of fiddling to get it to fire and run?

Does it ideal okay hot and cold? What RPM? Any changes to idle coincident to the ruling roughly concern?

Does it lack acceleration or is it as fast as ever?

Any rpm range where the running roughly is worse or better?

If you put your hand close to the tailpipe when it's running, what do you feel?

It could be a very simple problem, so don't go wild swapping parts (yet, if at all).

 

i do appreciate the help, more than a little out of the loop here, living in the country.

1966, 327, 350HP, M21, conv.
2 small pieces of metal, smaller than BB, closer to match head, never tested for magnetic
the timing of the tach not working to rough running very coincidental, but never noticed more exact coincidence than that.
currently always has a consistent and steady small vibration, cold or hot. at all RPM's
never tested performance, just delicate driving, thats why i dont want to take it on the highway
the dist cap and associated parts under looked normal, except for the metal bits
disconnected the tach cable, very frayed at end, did not look proper to me, did they have a finished end on them when new?
exhaust, the passenger side seems/feels/sounds normal, the drivers side seems to have the most significant change, not smooth, more than normal rough sounds.

 

You got to start with the basics. Check timing, check points ( adjust as NEEDED). Make sure all 8 cylinders are firing. Make sure all the plug wires are right and secure. Check the cap for defects and the rotor. This is a very simple to diagnosis and there is simply no reason to throw parts at it hoping to fix it. If you want to try it your self buy the GM service manual. It will get you pointed in the right direction.

 

Pictures and videos are always a great help when trying to find a problem. If you can post some here, someone may make a good guess as to the problem.
In addition, if someone in your area is in to old cars, video conferencing can be helpful to connect with someone who will take the time to watch and listen as you perform the troubleshooting at his direction.
The doctors are diagnosing you health via video conferencing, why not a mechanic?

 

What color were the metal pieces? Same color as the studs on dist cap?

 

You may want to consider buying a dial-back timing light as a good investment. They can be used to check timing, dwell, rpm, and by moving the pickup among the 8 plug wires can sometimes show a really bad cylinder. They can be had for about $100USD.

 

It sounds like an ignition wire is bad.....or maybe on the wrong cylinder. The #5 and # 7 plug wires are easy to switch and will cause a condition like yours. Make sure all the wires are in good condition, routed correctly and on the right cylinder.

 

Definitely do not pull the distributor, this will cause a lot of additional problems for you. The ignition contact points can become corroded causing a misfire or a no start condition. Can you post some photos of the metal debris that you found and possibly a close-up of the point contact area ?

Ray

 

thanks for all the feedback, i do appreciate it. I had to take off for a few days to help a daughter, back to vette now

once we thought we understood the metal source (the guess was tach cable - now we know not) i tossed the little metal bits, did not look like pieces from distributor cap, but will reinspect

plugs have been replaced, fuel has been replaced, wires remaining in a known placement/orientation, not a crossed wire.

will replace points and condenser, get a timing light on it, do my best at the points

goal is to get it to run better so i can drive it to the city... 30 minutes away for final setup by proper mechanic

back to this soon, with thanks.....reg