Thanks for all the follow-ups on this. Sorry it took so long to reply (two young kids make it hard to find time to work on the car, etc.)
Bob,
Sorry if I wasn't clear in my last follow-up, but I believe I do get your point about the adjustment. If I understand you correctly, your method guarantees the lobe's heel is in the correct position when making the adjustment to a particular valve.
Granted, I didn't adjust the valves according to your method, but rather according to the factory manual's method. Based on what you say, does that mean the factory manual method is inaccurate?
With any given cylinder at TDC with both valves closed, My understanding is there's a fair amount cam rotation with 0 lift before the lobe's ramp begins to push the lifter. So, if that's true, there should be no lift for about 90 to 100 degrees, since the base circle of the cam is providing no lift, and since the heel is in the middle of the base circle, it should provide an equal amount of lift (none) on the entire base circle between the ramps.
I decided to try your method against the factory manual's method, and I saw one or two thousandths difference between both methods.
For the sake of argument, however, let's say my adjustments were off. If that's so, that still doesn't explain why I am consistently getting more clearance when hot as when cold. I do understand what you mean by limitations of email. One needs all the data to evaluate any given problem.
I also concur with your thought about the engine build. It is an unknown about the internals, and based on what the car was like when I bought it eight years ago, I myself was very leery about the how well the engine was rebuilt.
When I found this problem happening, I had hoped someone out there would say "Oh yeah, we see this happening with all the latest Brazilian heads." Sound like, however, this is not the case.
Sure enough, I take it out every morning and, as before, it starts up as quiet as can be. As the seconds roll by, the tapping gets louder and louder.
When I re-adjusted the valves this past weekend, what I found this time were cold clearances of 0.010 to 0.012 at all the valves. When I re- adjusted them, and ran the engine, the warmed up engine noise diminished considerably, but it is still noisier hot than cold. Hmmmmm.
I took another look at the adjusters, and they are not as bad as I had thought, but I replaced them with swivel feet just the same.
I misspoke in my previous email, the push rods are not steel, so they are apparently not the issue. I had the same thought about the expansion rate of steel vs. aluminum, and pulled out my old materials book to calculate the difference in expansion for the two metals. For an 11" rod, the difference in expansion length is almost double for the aluminum. Roughly 0.020" for aluminum, and roughly 0.010" for steel. No wonder the cromoly rods are known to cause chatter.
After installing the swivels, I warmed up the engine for about 5 minutes, and heard the valve noise increase. I'm going to drive it for a while longer and see how it goes. I'll let you know what I find.
Thanks for your help,
Tom