Hello !!

Lets say i bay used crate engine. I just want to open it check bearings and rings. I dont want to take pistons apart because they are pressed in. But i do liked to balance the crank.

Lets assume piston/con rod combos are really close to same weight all 8. Can i just use that weight for balancing the crankshaft ? Then only error margin would be in the piston vs con rod weight ??

Am i right here or not ?

 

No. Reason being is that the connecting rod is both rotating and reciprocating weight. Every thing that is reciprocating, piston, rings, pin have to be weighed separate. Rod has to be weighed as a whole then the rotating or bigend has to be weighed. The reciprocating end or small end weight is achieved by subtracting the rotating weight from the whole weight of the rod.

 

Agreed. All things must be weighed individually and you must mix and match the components to get as close as possible to all of them weighing the same. Then the crank must be spun with bob-weights at the approximate operating rpm on a special machine designed specifically designed to balance cranks. Then you either remove weight or drill holes in crank where they press in specific amounts of heavier metal slugs to add weight. So definately leave this job to the pros, and as far as if this is necessary I would say don't fix it if it aint broken!

 

Thanks Guys!

Now i got it !!