Rotor Hitting Distributor Body Contacts

[spdway1]

My AA started skipping, popping, and running rough. When I took the distributor body off there was a lot of brass shavings from the rotor hitting TWO of the contacts. What would cause this all of a sudden? Thank you.

[ndnchf]

Worn out distributor bushings.

[JayJay]

Or a cracked rotor around where it fits over the distributor shaft…

[nkaminar]

A couple years ago I found that the plastic housing (distributor body) I had put on the distributor did not fit tightly and the gap was different depending on which way I pushed on the housing. I found a housing in my collection that fit tightly and that gave uniform gap on all contacts. (I am not sure if contacts is the correct name as the rotor is not normally contacting them.)

After that I set the gap by bending the brass part on the rotor until I had a very small gap. The specification is for 0.025 gap but I found that my car would run a little better with a smaller gap. I ended up with about 0.010 gap. That will only work if there is no slop in any of the parts: rotor, housing, or distributor shaft.

I suggest examining all of the parts, looking for a cracked rotor, as Jay Jay said, or worn bearing in the distributor, as ndnchf said, or a loose housing.

[Bigsnapper43]

I don't use the new Dist.body!!! I have found too many that are not round. I suppose his unit got hot and warped. I just clean up an old unit. 99.9 work fine. The problem area is where the spark advance rod passes close to the 3ed plug wire. Start the car after dark and look for a short. The old unit works just fine...

[jw hash]

Sponsored Links (Register now to hide all advertisements)

Big, is right on. I have seen some that are egg shaped. set your timing, loosen up your dist, cam. put your rotor on and turn the rotor and check the gap at each contact. they should be all close to the same. I don`t remember what that gap should be. maybe someone can put that Number on here.

[JayJay]

Originally Posted by jw hash

Big, is right on. I have seen some that are egg shaped. set your timing, loosen up your dist, cam. put your rotor on and turn the rotor and check the gap at each contact. they should be all close to the same. I don`t remember what that gap should be. maybe someone can put that Number on here.

The standard spec is 0.025”. But frankly, a bit closer won’t hurt at all. You need to reset timing after fiddling with the gap.

[spdway1]

UPDATE: The distributor shaft has NO play (side to side). With another new cap and rotor from Snyders, Position (cylinders) 3 & 1 have a proper clearance of .025. Position (cylinders) 2 & 4, the rotor hits the contacts on the distributor body. I have tested this by turning the engine over with a crank. What can I do to fix this with what I have on hand?

[Gold Digger]

If I was going to use that cap I would file the tips inside the cap on the one's that were too close. Or otherwise find another cap.

[nkaminar]

Gold Digger has a good suggestion. But make sure that the cap fits the distributor snugly before doing any filing. If it is loose, get another cap.

[Fullraceflathead]

I have worked in quality control with injection molded plastic for many years I've got a sneaky suspicion that they're running these caps and distributor housings at too fast of a cycle on the injection molding machine and they're coming out too hot and a little bit soft like putty and they are warping oval as they cool. I'll bet, if you measure across the pins with a pair of calipers you're gonna see that the housing is oval. The old original caps and housings were made from Bakelite and that's a whole different piece but the modern material is not the same as the old Bakelite!!!

[CT Jack]

Many good tips posted. I prefer to mount the distributor in a vise with the points, rotor and cam removed and indicate the runout of the shaft. This will identify if the bushings are worn and in need of replacement. Runout should be > .005". This is the most important 1st step. Too much runout will cause a variation in point gap and can also cause the rotor to make contact with the contact pickups on the inside of the cap. There are many cap manufacturers and some have produced caps with variations in the height of the contact pickups. Measuring the gap between the rotor and the pickups should be uniform as noted in post#8.

[Big hammer]

Originally Posted by spdway1

UPDATE: The distributor shaft has NO play (side to side). With another new cap and rotor from Snyders, Position (cylinders) 3 & 1 have a proper clearance of .025. Position (cylinders) 2 & 4, the rotor hits the contacts on the distributor body. I have tested this by turning the engine over with a crank. What can I do to fix this with what I have on hand?

Please let Synder’s know of your issue ! File or grind clearance on # 2 & 4 contacts

[Y-Blockhead]

Originally Posted by CT Jack

Too much runout will cause a variation in point gap and can also cause the rotor to make contact with the contact pickups on the inside of the cap.

Not to mention varying the timing as the point gap changes.

[katy]

Originally Posted by Big hammer

Please let Synder’s know of your issue !

Ditto

[nkaminar]

CJ Jack, I think you meant to say that the runout should be < 0.005 not >. (Less than not greater than.) 0.005 seems a little too much to me. I would shoot for 0.001 or less.

[CT Jack]

Neal, yes my error. It should be <.