Hi Folks, been reading the messages about V8 and V7 crankshaft balancing
with interest. Some of the ideas seem confusing to me. I thought I
would quote an authority so the novices reading the discussion might
understand what is being talked about.
P.E. Irving, "Automobile Engine Tuning", Temple Press, London 1963,
Chapter 13, "Balancing", p. 141: "V8 crankshafts require dummy weights
on each pin; each weight must be equal to the combined weights of the
TWO big-ends, plus the top-end weight of ONE connecting-rod and its
piston, rings, etc., ..."
In this procedure, bobweights as above are attached symmetrically on
each crankpin and the crankshaft then rotated at 1000 rpm in a balancing
machine. The crankshaft is then corrected by drilling holes or adding
"heavy metal" in the counterweights until it is in balance.
It is assumed that all four sets of pistons and con-rods have an equal
weight to 1 gram and good luck achieving this in practice!
The weights of the big and small ends of the con-rods have to be
measured horizontally on a frictionless device to get accuracy.
Speedway Motors sells such an item for this purpose, how good it is I
know not.
I imagine that for a V7 a steel sleeve clamped on the crankpin, taking
the place of one big-end, to seal the oil hole in the crank and take the
side thrust from the working con-rod, and the said sleeve weighed 50% of
the original balancing bobweight, then the crank balance would remain
correct for all practical purposes.
I suppose that the previous messages about 50-51-52% balancing have a
relationship to the above information, and perhaps people would verify
that for me.
The man who does my balancing seems to be willing to do it in accordance
with Irving's model. It's his machine, and I can't run it.
Cheers from Ardun Bill in the Great Dismal Swamp, Chesapeake, VA, where
it's been in the high 60s the last four days so I could get my bike out.
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