On the subject of max. rpm's.....I think you have to take it on an engine by engine basis. I just got my rotating assembly back from the balancer. He concluded that the rods in my 60-235 engine, were so far out of whack, that he replaced them with a good set. The weight variations were as high as 13 grams off. Fortunately, he had a set of balanced rods that he graciously donated to the cause.
This engine had been rebuilt by the PO and had been running with this unbalanced situation. I'd venture to guess, that it would have had a substantially lower red line than one that was closer to being in-balance. Can't even imagine what was happening inside the engine at even 3000 rpms!! Generally speaking, the standards in the 50's and 60's weren't quite as tight from the factory....let alone, when some backyard mechanic slapped a bunch of mismatched parts together, and made an engine.
I think that anyone who is rebuilding a vintage 4 main engine, would be wise to invest in getting a balance job, even if they aren't intending to max. out the revs on a regular basis. It would be a shame, to spend big bucks on a bore job, cam, bearings and everything else that goes in, without insuring that the whole package will be as smooth as silk all the way through the power band. Mine will probably never see 3500 rpm's, but it won't be trying to self destruct with each rotation of the crank.
I was a bit skeptical when my builder strongly suggested getting it balanced, but am thankful I took his advice. I think it will turn out to be money well spent!!!
Dave
