'60 Contact points keep closing

[Ted L.]

I can't understand why the points keep closing up after about a half hour of running. (230 HP single points). The adjustment screw is not moving because I put a mark on it and it stays the same. I check the gap when the engine starts backfiring and sure enough, they've closed up (or nearly so). After pulling sandpaper through them and readjusting to .016 I can expect them to close up again in about a half hour or so. The cam on the distributor shaft looks good. Anybody else ever experienced this?

Ted #32350

[Stephen L.]

Re: '60 Contact points keep closing

Just a couple of thoughts......
Could the "locking" screw be too long and bottoming out before the points are fully tightened?
Is the "rub" block that rides on the cam wearing prematurely or loose on the rivets? (This did happen to me.... new points and the rivets loosened due to spring tension)

[Roy Braatz]

Re: '60 Contact points keep closing

It's not the adjustment screw , but the lock down screw that must not be fully seated on the points as you tighten it down.Could be striped or bottoming out, could add a flat tooth lock washer under it.

[Doug Flaten]

Re: '60 Contact points keep closing

Could it be that the distributor shaft bushings are loose and you have some play in the distributor? I had this happen on my old Harley when I purchased it. I would set the points and timing, and it would run fine for a a while and then start backfiring. When I checked the point gap, it would be different than what I had just set. I lived with it for months until I decided to pull the distributor. Anyway, the symptons sound awful familiar.

[Ted L.]

Re: '60 Contact points keep closing

I'll check tomorrow, but I don't think there is a lock down screw. If you adjust the points through the window (like you would if you had a dwell meter) there wouldn't be any way to tighten a lock down screw. I'll also check the rivets and rubbing block for wear. Thanks for the response, you've given me some places to look.

Ted #32350

[Roy Braatz]

Re: '60 Contact points keep closing

Even points that are adjusted through a window have locking screws TWO for the points were the points are held on to the Dist plate. You may have a week spring that holds your adjusting screw.

[Duke W.]

Re: '60 Contact points keep closing

Pulling sandpaper through the contacts could have something to do with it. NEVER, EVER use sandpaper on an electrical contact. Sandpaper is made from aluminum oxide and other non-conductive material, and the residue it leaves behind will reduce the actual conductive contact area, which could lead to high resistance and burning of the points.

USE A FILE - like a nail file - on points and other electrical contacts that have pits or oxidation and need to be dressed.

Considering that your distributor is over 40 years old and has probably never had a decent tear down and inspection, I would pull it and do a complete overhaul. Check the bushings for wear and replace as necessary, regrease the upper bushing grease well, replace the breaker plate and shim up the end play to two to seven thou. Replace points, cap, and rotor as required. Don't forget to install the drive gear with the dimple pointing in the same direction as the rotor.

One test of distributor health is dwell variation. Rev it up to 5000 while observing the dwell meter. If the dwell angle varies by more than 2 degrees your dist. needs work - could be sloppy bushngs, a wobbly breaker plate, or weak breaker arm tension. With SHP engines rev to 6000 using the high breaker arm tension points and look for no more than 2 degrees dwell variation.

Duke