thoyer

Took my cap off today. Lots of brass dust. Looks like rotor is hitting the cap terminals as there are grooves worn in the terminals. Car has only been run a few hours if that - just breakin.

How much gap should there be between the rotor tip and the cap terminal?

Both cap and rotor are "reproduction" parts.

283/245 with dual point mech advance distributor setup

Tom

1restoman1

Don't know the clearance, but sounds like the distributor bushings are worn, allowing the shaft to wobble and the rotor contacting the cap. You will need to pull the distributor to check side play in the bushings. you can't feel it while its mounted on the engine.

thoyer

Good idea, but distributor has been freshly overhauled - no bearing or end play issues.


Tom

MikeM

Can I assume you have the cap oriented to the distributor body with the tooth on the cap down in the notch on the distributor?

wraplock

I had the same problem on a car I purchased. The cap that was on the distributor when I bought it worked fine. I tried 3 or 4 sets of rotors and caps and they all hit. I went through the bills for work the seller had given me and found that the distributor had been overhauled. I call the company that did the work and they said to send it back. They found that the pad that the rotor mounted to was attached to high on the shaft. They repaired it no charge. I would imagine you could measure the rotor mount and compare it to another known good distributor to see if you have the same issue. Sorry I don't recall who the rebuild shop was but they where a well know distributor restoration shop....I think in Florida. I could be wrong it was years ago.

thoyer

Looks like I need a rotor with a shorter tip...... Took an old cap and cut a window in it so I could see the rotor tip to plug post clearance. The gap is minimal. From what I could find, the gap should be 0.08 to 0.100" or so......

Also measured the distance between posts on the old cap vs the new one. The new one is about 0.030 closer plus the new rotor tip measures about 0.015" longer then the old one. These two combine to give an interference fit with the new cap and rotor.

Most of the rotors I see for sale have a long tip just like the two I have. Came across this one which has a shorter tip and looks like it would provide a larger gap.

http://vettegirl.com/product/corvett...r-delco-rotor/

Checking the usual suppliers, they all show the longer tip version. I suppose I could file the one I have down to provide a larger clearance.

Tom

Plasticman

Just as a further check, try checking shaft / bushing side play in several directions. Bushings wear "egg" shaped, and it sure sounds like you are seeing it.

Good luck,
Plasticman

thoyer

Check post #3. Shaft and bushings have all been checked and there is no excessive play in any direction.

I'm convinced the problem is with the rotor. Cut a notch in an older cap. Picture shows the minimal clearance between the rotor tip and the post. I believe the rotor to post clearance should be around 0.080". that is no where near what I'm seeing.........

Frankie the Fink

Weird.....never had that problem in 50+ years...

thoyer

Frank,

I could write a book on this car. Been fooling with cars as a hobby for 35+ years. This car makes me feel like I've never turned a wrench before. Every nut and bolt on this car has come with baggage! I swear this car is possessed in some way or another. It is a love / hate relationship and to be honest there has not been much love over the past two years...........

I put a 60 together a few years back and that car didn't give me any trouble to speak of. My 71 big block was was easy also. Built several other cars over the years - including a 9 second big block Camaro race car. Do all of my own engine building (the only thing I don't do is paint and automatic transmissions) and have learned many things the hard way. I'm still learning and this is just another instance of either I have the wrong parts, the parts are made incorrectly or I'm doing something wrong. I try to rule out my shortcomings before asking questions, but in this case I'm not so sure if it is me or something else.........

Tom

AZDoug

At this point, I would say the cap has been "broken in" by the rotor, just clean the brass dust out and run it.

The large clearance rotors, were, I believe, an emission thing.

I also don't recall seeing rotor conductors that were so shielded by the plastic, they typically extended out from the plastic/bakelite some distance.

Doug

Bill Pilon

Tom, I had the same problem about 6 months ago when I changed the cap and rotor on my 60, I used new Standard Motor Products, the same as I have used for many years. I called the company and they said they had some problems with that cap and rotor combination, they sent me a new cap and rotor over night, same part numbers, installed them no problems since.