Posted by John M on Saturday, February 04, 2006 at 8:56AM :
I rebuilt my 230 flathead engine about 4 years ago and haven't had a problem since. It has had very low miles in that period, I'm guessing about 10,000 miles, maybe less. Now this was a poor mans rebuild. I never removed the camshaft or valves. New pistons/rings, crank bearings and related machine work and machine the head was all I did other then gaskets and water pump. Still there haven't been any problems mechanically. It gets driven once every couple of months. The first Christmas after the rebuild we drove it from Phoenix to Houston and back again with only a set of burned out points. Today I noticed a very specific engine noise when I hit 3000 RPM's. It almost sounds like valve float in a conventional valve train but not quite. The noise starts almost instantaneously and ends immediately after dropping the RPM's below 3000. There is no change in oil pressure or engine vacuum during the event. The engine appears to get a 4 or 5 degrees hotter during the event though I wouldn't want to bet my life that the two are related.
Describing a sound in words is difficult so the following word picture is odd, but is the best I can do. Over the engine noise this sound sounds almost like a recorded applause track that you might here on a TV show from the 50's or 60's. Imagine a sound technician flipping a switch for applause and you hear instant applause at full volume. The sound ends as if someone turned off a switch.
My first assumption is that it is time for the routine valve adjustment/maintenance. I thought I would bounce it off of this group before I started down that road. What do you think it is?
If it makes a difference the engine block is actually from a 1953 pickup and based on the observable wear had been rebuilt within the last 20,000 miles before the vehicle I took it from was junked. The head is from a 1952 Pickup and was machined during the rebuild. I do routinely check/re-tighten the head bolts every couple of thousand miles. I follow the correct procedure.
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