Today I have a little story to tell. It's a rather interesting story. When I first built this engine, I had a couple of very fast, very good runs with it. I knew at that time that with some finessing, the engine would be a good runner, and it would be safe to sell plan sets for it. I like my engines to run slowly---in fact, the slower the better, as far as I'm concerned. I could never persuade this engine to run slowly, and for the last few weeks I've been struggling to find out why. When I make my cams and lifters, I make them from 01 tool steel, heat to red hot with oxy acetylene torch, and drop them into a can of motor oil. This thru-hardens them, and since they never see a lot of "shock" loading, I don't bother to re-heat them and draw them back to a softer state. The model of the cam which I have attached has a 5/16" bore (To give you an idea of overall size) and four drilled and tapped #5-40 holes around the shaft to lock the cam in place on the shaft. The ONLY reason to have four holes is that when I time my engines there is limited access to the set screws, and having a tapped hole every 90 degrees guarantees that I will be able to reach at least one of them to tighten the cam in place on the camshaft. Today I disassembled one of the camshaft supports, and removed the camshaft, to get a better look at what was actually happening. The threads were put into the cams before they were hardened. For some reason, and I don't really know why, the threaded holes were "closing up" near the bore. I found that when I had the camshaft removed, a set screw would thread into the holes in the cam like they were supposed to, but when fully tightened, they weren't locking the cams onto the camshaft like I thought they were.--the screws were binding up in the tapped holes and putting very little locking pressure on the shaft!!! Of course, this would initially let the engine start and run, and then the cams would slip on the cam shaft and throw the engine out of time. I have some very good #5 taps, and when I ran the tap thru the previously threaded holes, the tap would try and lock up in the hole before it broke thru into the bore of the cam. As I said, they are very good taps, and with a bit of light cutting oil and some serious butt clenching, I was able to run the taps all the way thru into the bore of the cams. Now the set screws will go in full depth and bear against the camshaft to lock the cams in place. This is probably my fault. I should have ran the taps thru the tapped holes immediately after hardening the cams.---Brian