IMHO, Simple answer - yes. When you change the weight of reciprocating parts, you gotta re-balance the rotating assembly. The engine will live much longer - and run smoother as well.

If you need to convince yourself, weigh the pistons/rings/wrist-pins separately from the rods and rod bearings, and get the OEM weights of the same parts and compare them. If you're lucky the parts will have identical weights and you don't need to re-balance anything. Otherwise, get the engine balanced.

 

will even a few grams of weight difference have drastic effects if not rebalanced? like if the OEM piston weighs 93g and the CP pistons weigh 90g, and it goes together without balancing, will this be very bad for the engine?

 

It's your engine - you get to decide. A quick conversation with your engine builder will be the best way to answer your question.

 

I went to high compression and rebalanced. The engine builders told if I went from 11.1 to lets says 8.5 to 1 and went lower with weight then it is okay to be overbalanced. Not good to be underbalanced though. That is coming from Total Engine Concepts in West Palm

 

thanks guys , I really appreciate it

 

11.0 is really mild. any reason you didn't go higher? it really doesn't add hp anyways so I guess it doesn't matter...

and yes i would balance the entire rotating assembly.