<VV> Rod caps and balancing

[tony.underwood at cox.net]

---- "D. Barry Ellison" <bars84crx at hotmail.com> wrote: 
> 
> I would vote against it.  Due to dropped valve seats damaging pistons which I could not acquire replacements at the time, I assembled an engine with 4 pistons of one type, and 2 of another, with the 2 odd ones at #3 and #4, all .040 over.  I don't remember how much they're off from the other 4, (seems about 60 grams, but I honestly don't remember).  Balanced pistons and rods individually L vs R.  

   I've put engines together by matching weights of opposing pairs and never had any vibration issues.    It sometimes involved the numbers stamped on the rods being haphazardly assigned, #6 rod in #2 spot etc.   The way a 'Vair engine is put together is pretty much tantamount to three 2-cylinder engines sharing a common crankshaft.   The opposing pairs of rods/pistons simply don't interact with other opposing pairs... unless something is VERY MUCH different as regards weight and even then it's not gonna amount to THAT much vibration.   

This is why a 'Vair crank gets away with having no counterweights.   



> Over 5k, the motor vibrates my teeth smooth.   

If the opposing pairs are balanced together, this shouldn't happen.   Maybe something else is going on here... 

Were the big ends of the rods weighed independently and matched...?    That's where most upper range vibration in a 'Vair engine is likely to come from, all else (as in common sense items) considered, if the big ends don't match; total rod weight notwithstanding.   



tony..