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Put in a set of new points about 500 miles ago. Timed with a vacuum gauge and went on my way. 35 miles later ...no more rubbing block. The rivets that held the block to the point arm failed. "Blue Streak" brand. Because I have used this brand before with no issues I looked for a wobbling shaft. Not. pulled the dizzy apart and cleaned up the shaft, mechanical advance and made sure that the gear was good to match the cam. Good tip from this site.Put it all back together. Added points, condenser, cap and rotor all from Autozone. 100 miles later the truck started surging on the hill coming home. 55-57 235 in a 52 1/2 ton truck. After about a useless 2 hour timing and carb adjustment I Finally remembered I have a Dwell meter...Duh! Dwell was 6 degrees....that equals bad point gap. Adjusted back to 0.0017 and truck ran fine. Adjusted with vacuum gauge and was back on the road. For about another 100 miles. problem came back and sure enough the point gap was too small again. Dizzy came back out. Point cam is smooth, coated with just a bit of the lube you get with the points. Shaft is not wobbling and the mount plate is tight in the housing. What am I missing? Might be simple but so far it has escaped me. Thanks Steve

If you are running on 12 volts maybe the coil & resister don't match & you are over heating the points. Do they look burnt?
The points we get now are not good quality because they don't sell many any more. Maybe you can find some NOS.

I vote for a missing ignition resistor, or a bad internally resisted coil, making excess zap on the points as George says

Bill

You state in your first past that the rubbing block was worn down. That has to be a mechanical problem, not electrical, unless the second set of points are burned, not worn at the rubbing block.
Logic would be that the points cam has some slight defect tearing up the block.
Might be a good time to switch to a Pertronix.

I have an internal ballast coil. And yes I am at 12 volts. I do have another dizzy so might be a good time to switch it out and see what happens. Points are not "burned" they are "grey" but not pitted. I did use the "heavy duty" type cause they have a vent hole in them. No dollars for that Pertronix but might put it on my wish list. Thanks again for the help and ideas. Might put on the 5 volt coil and a resistor as well but I want to do one thing at a time. Helps me learn if you know what I mean?
Steve

I was thinking the loose rivets could be caused by excess heat.
If I remember my arithmetic, 6 degrees would mean a wider gap.
I havn't used a dwell meter in a long time.
It seems at $10-12 a crack for points you could get that petronics. Make sure the coil matches though.

are you sure someone hasn't replaced the hold down screws for hte points with a metric thread or something? I guess it's possible and within certain number of miles, it's backing off and the points move and reset themselves??? It sounds like your points aren't burning due to too much voltage, sounds like they are physically backing off from gap. What is the gap when this bizarre event occurs, did you measure that? .30 or more or ?

I had a situation years ago when I was renting VW campers. One season points began to close up on several of the engines. Cams were perfect. Tried red "sticky" grease, not much help, silicon grease worked a little longer. The rubbing blocks were wearing down.
I always bought the same brand of points and never had a problem before. Changed brands and the problem went away.
Must have been a batch of bad material at the manufacturer.

Jeez, does this mean we have to start measuring the block when we install the points so we can see if It's the fail point?

I wonder if there is some kind of website that kept track of venders, batche #'s etc. of bad parts? An Emily's List for part #'s...

Point gap is closing over time. It should, just not this fast. When I checked I put the rubbing block on the "point of the cam and put in a 0.0015 feeler gauge. My version of the "go-no go" gauge. It would not fit. Adjusted to 0.0017 with a very slight drag. Big adjustment to get that gauge in. Plate is stock and screws are original. One off set that has been peen'd to the cover and one that clamps the points base in place. Jim Sears might have the best observation. At least it matches what I see. Thanks to all. I think I got a bad set of "Blue Streak" and it just got worse from there. A list of trouble parts could be helpful. A list of complaints about local parts guys might not. The "social" side of information needs to be moderated a lot. Thanks again. I really don't want to pull that dizzy if I don't need to.
Steve

Steve,

Most likely you mean .015" and .017" point gaps?

tclederman: Yep. Up date: What I found....I have 4 dizzys. All are a bit different. With 3 different case heights and 2 different shaft lengths. If you mix a short shaft with a tall cap and rotor, you will have issues. The rotor will rub on the points and that was why the gap was changing. So cause I had one. From a 216 with the short shaft, short clips, and a short cap and the right cam gear I changed to it. My "stumble" just off idle went away. My truck starts easy. Idles smooth and reliably and the Vac advance works fine. Best guess, 1949 216 truck dizzy. into a 1955-57 235. Good news, it works just fine and with the 216 valve cover not too many will know it ain't stock. Now if I can stop the oil leaks.

It is not a good idea to use a distributor designed for a steel cam(216)in a 1955-62 235 with a cast cam. You will see premature gear wear, although it will run a long time.

Pre'68 Dave: I think it was your blog that helped me figure what gear went with what cam. Compare the width of the cam gear was posted. If not yours then some one else on this site. I am still amazed at what can be found on here.