I took apart my ls to put in p30 pistons and put in arp rod bolts and all new seals and rings and pumps, etc. Im also going to hone the walls and resize the rods for arp rod bolts but besides all that is it really necessary to get the rotating assembly balanced? everything was in great shape when it came apart.

 

bunmppppp

 

not necessarily, if it was all good when you took it apart youll most likely be fine, personally i would do it just for the peace of mine especially since everything is going to be torn down.

 

what would be the downside of not doing it or what happens if i do?

 

Good question, I would get it balanced to reduce harmonics at higher engine speeds that can break oil pumps and cranks.

Since it's just a rebuild with stock parts for a street engine? you can get away w/o balancing.

 

yea its a street engine but once in a while i want to rev it high and see what it can do. Im putting type r valvetrain and cams in the b16 head so I want to be able to use them to their potential.

 

bumpppp

 

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bumppppppp

 

Are you bumping because you are waiting for someone to tell you don't have to do it or you do have to do it? It is always recommended that you have the rotating and reciprocating assembly balanced especially if you plan on reving it higher than stock redline. Its not going to cause many problems if you don't, although as someone mentioned, harmonics can destroy the oil pumps and cranks. Make sure your harmonic balancer is in good condition or by an aftermarket one. Other than that you may experience engine vibration if you do not do it.

 

You should absolutely re-balance everything. This is especially true if you are going to rev the **** out of it. There are two reasons for balancing. The first is harmonics, strange harmonics can cause stress cracks in the block. Second, if the rotating assembly is not balanced it will put undue strain on the bearings and at higher RPM you can actually trash the mains pretty easy.