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Posted by: funk Jan 16 2015, 01:07 AM

I have a mech who says I should put the internals on a balancing machine. It costs 225$ I have read books saying you can use a small grinder to grind the heaviest rods, pistons ect.. then weigh on a scale for balancing to within a 1/2 gram this mech thinks a balancing machine is far superior and well worth 225$ Any advice? and if I did use a dremel on the rods and internals how do you balance a fan??I couldn't find any literature?thanks just for kicks I also spoke with a retailer/mechanic who states that type four motors don't need to balanced??

Posted by: funk Jan 16 2015, 01:07 AM

I have a mech who says I should put the internals on a balancing machine. It costs 225$ I have read books saying you can use a small grinder to grind the heaviest rods, pistons ect.. then weigh on a scale for balancing to within a 1/2 gram this mech thinks a balancing machine is far superior and well worth 225$ Any advice? and if I did use a dremel on the rods and internals how do you balance a fan??I couldn't find any literature?thanks just for kicks I also spoke with a retailer/mechanic who states that type four motors don't need to balanced??

Posted by: Joe Sharp Jan 16 2015, 03:40 AM

I balance the pistons to the 1 tenth of a gram on my triple beam and have a fixture for the rods. I have no way to do the crank, fan, flywheel and the clutch. $225 seems OK too me. All this is fine but you still don't want to rev past 6K because of the valve springs.

Posted by: Steve Pratel Jan 16 2015, 06:23 AM

You can balance the pistons and c rod assemblies by weight, but the crankshaft fan and flywheel must be spun. The engineers did a decent job, but it doesnt hurt to add a little extra effort in this area.

I balanced my pistons/rings/bearings/rods on a digital scale. Used a small grinding stone on my dremel to lighten the connecting rods to balance. Got everything to within .25 grams

I sent the crank, fan and flywheel out to be balanced. They did the crank first, then added fan to the assembly then the crank and balanced. They did not want the flywheel or clutch.

The fan was spot on but the crank and flywheel needed to be I also had them mic and polish the crank, total was $375, but I am in Northern Virginia where everything is more expensive.

Posted by: Mark Henry Jan 16 2015, 07:28 AM

QUOTE(Steve Pratel @ Jan 16 2015, 07:23 AM)

Posted by: Tbrown4x4 Jan 16 2015, 07:36 AM

^^^ Agreed. All rotating parts should be attached when balancing. But......all I have ever had balanced was an inline or V-motor.

Posted by: stugray Jan 16 2015, 08:24 AM

My local machinist did my entire rotating assembly for $200.
Fan, crank, rods, pistons, FW, pressure plate.
He even wanted the rings for exact weights.

I didnt watch, but I dont believe that you need to attach the "BOB weights" when balancing a boxer.
Probably doesnt hurt though.

Posted by: rick 918-S Jan 16 2015, 09:32 AM

Balancing machine? I'm old school. There is more to balancing the just grinding metal off the big end and or small end of the rods. Improper execution can result in weakening the rods. Have it done or read, read, read before you start. Besides, the parts are balanced at the factory and should be close enough for a stock rebuilds. It's when you are pushing for more performance that you start blue printing the parts. There are formulas to what a rotating mass and it's assemblies should weight for max HP and longevity.

The fan is balanced. sometimes there are little weight clips on it. (I think) If you want to check it bring it to someone that has the equipment to balance a flywheel.

Posted by: McMark Jan 16 2015, 10:23 AM

There's a big difference between balancing rod total weights and balancing rods end for end. The latter is superior and requires more than a grinder and a scale.

Posted by: Mike Bellis Jan 16 2015, 10:26 AM

I would suggest dynamic balancing with the crank assembly spinning. This is far better than only making the pieces weigh the same.