[T2] weighing and balancing the piston - advise

[John Anderson]

Chris, I don't know about it making the difference to 100000 miles, but will make it run smoother.  I'm guessing that is about 9gm difference, top of my head, and that is a lot.  Easiest way to remove is drill holes in the back of the piston up at the thick part around the pin.  Multiple holes if needed.  I balance pistons, and pins individually so that you don't have to keep things straight, though functionally it doesn't matter.  Grinding the inside of hardened pins, is hard to do, and the pins are usually pretty uniform themselves.  I strive for 0.1gm on a good O-haus balance or now days I'd use a cheapo digital (I'm about to build an upright for my SC) I guess for a race engine, but for routine rebuild, you get em to 0.5-1.0 gm you are doing pretty good.
 
With a digital you can end for end balance the rods as well easily enough, you just need an old lab test tube stand.
 
Or since you really need it all spin balanced (with the flywheel, fan, clutch cover and disk) anyway, you can probably just toss the guy an extra $50 to do pistons and rods.  Though it does give satisfaction to do it yourself.  You'd probably be better invested in cc'ing the heads and adjusting those yourself, and taking the time to match the deck heights carefully matching longer rods to shorter pin heights.
 
Again will it make a difference who knows, but it isn't a lot of effort, and fully balanced engines (rotating parts spin balanced) definitely run smoother.
 
John
 

________________________________
 From: Christophe Guilbert <cguilbert at picasso.ucsf.edu>
To: "TYPE2 at type2.com" <TYPE2 at type2.com> 
Sent: Wednesday, November 13, 2013 4:24 PM
Subject: [T2] weighing and balancing the piston - advise
  

Hi ,

I was weighting my new piston to balance them.
3 of them has the same weight but one  is 0.3 oz less than the others . 
should I remove 0.3 oz from the 3 pistons by grinding the inside of the 
piston pin ? would it make my engine last 100000 miles if I balance it 
that way or it won't make any difference.