Anthony,
RE:"On the cam front - the earlier US cam was better than the
late one (73 on)but neither are as peppy as the PI cam which
had much wider timing."
That may be true, but it's the opposite of my
impression. First of all, I don't think there is a "PI cam".
Rather there were 2, the early monster with 70 deg of
valve overlap ("150 HP") and the later one with only
36 degrees ("125 HP"). The later PI cam and the later
US carb cam were identical, I thought. The early 6
cam is what I have in my TR250, with only 20 degrees
of valve overlap. It's a torquey cam, I can climb gentle
hills at less than 2000 RPM in top without lugging, but
there's not much above 4000 RPM except noise...
Why the fascination with PI? Compare the
Post-1973 UK vs US engines. The US had 7.5 to 1
compression, lots of emissions BS, and managed
104 HP. The magic PI system, with 9.5 to 1, managed
125. Quite a difference, but why not just shave the head
and save a lot of cash and headaches? You'll get
most of the benefit, unless you're sure you'll
shift at redline each time...
Best,
Tom Marincic
CD3574L
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