How can you test or establish if a distributor shaft point cam lobe is worn? Either by measuring dwell (electronically) or eyeballing it? How often do they wear out on distributors? (any make or model) Thanks, ElectraJim PS, I just started playing with a point set in a car. Last time was over 22 years ago. :TU: :eek2: ElectraJim
Boy I'm with you on the long time since messing with points. We use to gap them with a match book and call it good. I decided the best way to deal with points was to get rid of them! I've never heard of the lobe wearing, but then again when I messed with points the "Old" cars were not as old, and with my budget we made things work without digging too deep.
..But it was soooo easy back when I did it. I learned on a distributor that had a slide open door, that you could set with the engine running. I had a budget "Actron" dwell/tach meter that I think I bought at Western Auto. The adjustment tool was an allen head end with a flexible shaft to a knurled edge handle. It was a sweet setup. ElectraJim
So, for a 4 cylinder distributor, would the lobe look like a perfect square with 90 degree angles on the edges? If smoother, how much smoother before it's considered "worn out". That's what I'm trying to figure out. If it's measurable. Ultimately, wear effects the coil saturation. o No: Tune up service recomends applying a lube to the contact surface. ElectraJim
You may have to look very close, but check the high spots on the lobe. If they are rounded over and scored, replace it. The tang on the points that rides on the cam is narrower than the cam itself, so it will create a wear mark/witness mark. compare that to the condition of the very ends of the lobes. An old school ignition scope should show it, if you have access to one. Yes, point lube is imperative. If not used, the new points will wear out in a matter of minutes.
Never seen lobe wear. More commonly, the bushings wear and the shaft wobbles which leads to large dwell variation with increasing RPM.
Larry, is right on.... the point cam is very hard, heat treated , steel... I have never seen one of them wear.... i have seen them rust.... but if the points are lubed right that will not happen.... like Larry said with high mileage the bushings will finally wear out and the shaft will start to wobble and cause the dwell to constantly vary... a stock nailhead dist. is hard to beat if it is ''blueprinted'' and maintained.... one of the better set ups that I have run, with the points, was a stock dist that I had rebuilt and took a set of stock delco points and bent the spring around backwards to make them go all the way to 7000 rpm without bouncing...[on the dist machine] and then used a old aftermarket capicitive discharge system that kept the points from burning out...along with a advance curve kit.... I could turn all the rpms with that , that the buick engine need to do... But, the best approach now, is to just eliminate the points...
Dang you!! I just put the Pertronix ignitor 2 in last night, and because of this thread I spent several minutes of my life that I'll never get back looking to see if I could spot any signs of wear! Obviously I didn't find any.
I hate to burst bubbles here, but point cams do in fact wear out, and it is not at all uncommon. I just pulled 4 old distributors out and looked at them and almost every one of them is showing significant wear. Will post pics tonight as camera is at home.
Steve, No bursted bubbles here:laugh: I've just never seen any, but I've always used that little capsule of cam grease they used to give you with the points back in the day. I've seen the little rubbing block on the points wear, but never the cam.
most show wear marks, but i have not seen any with grooves. then again i am not a mechanic and have not seen that many. jim ps remember these dist are over 40 plus years old.
The pics aren't all that great, but I cleaned this one to show what I would consider "average" wear on a 100k distributor. Remember, I was fixing these cars for a living in the early 80's. There were tons of 60's and 70's cars in the shop all the time. It's how I learned to do tune-ups etc. Rebuilding carbs, setting points, scoping ignition performance, etc was making a living. If you were to run you fingernails up one of these lobes, you would feel deep grooves and bumps. This rough surface will wear out a set of points in no time flat, lubed or not. If you have a scope, you could see the difference in coil saturation. It is huge. Not to mention having to adjust the points every 100 miles. Keep in mind that not all "rebuilt" distributors come with a new cam.
Those look like some kind of corrosive grease was put on them... see the white looking stuff there.... Ford taught us to use just a tiny bit of non fiber wheel bearing grease....it wont melt and run at engine temps... ever see a dist. cam where some clown put carbolic vaseline on it.....rusts like an old plow....:Brow:
I have a Mallory conversion in my old distributor and it works great! In the old day I used to keep a spare set of points and a dwell meter in the trunk becasue the points would alway choose the worst time to burn out..Never saw much wear but I would think that if you lubed the cam that the whole car would wear out before the cam would.
