Do I really need to balance my rotating assembly?
Do I really need to balance my rotating assembly? I had my stock crankshaft re-conditioned (cut 0.010" under) and polished, I am re-using my stock rods, and installing Mahle forged pistons. I was planning on weighing the pistons and matching with rods so all my piston rod assemblies are as close as I can get them. I will grind slightly if I have some that are noticeably off. If I take all these precautions I find it hard to believe that I would gain much from a balance on a engine thats intended use is a mildly modded street engine.
you wont gain much other then your bearing not falling apart or vibs in the engine. whats the weight of new and old pistons ? if there off just a little bit and u dont rev super high it can be done. still bad idea though
I haven't weighed them yet but by spec the stock ones are 434g and the Mahles are 398g.
I've talked to 3 different machine shops about my build. Which I'm using the crank that came out of my LQ4 and it didn't need to be turned. BUT, I bought a matched set of rods and pistons from a LQ9 (that crank wasn't available)
I'm having the pistons fly cut. The shop fly cutting, said he'd take the same amount of material out of each piston and he didn't see the need to balance since I was using all GM pieces. However, the other 2 shops recommended to balance since it would see 7000 RPM's.
I'm having the pistons fly cut. The shop fly cutting, said he'd take the same amount of material out of each piston and he didn't see the need to balance since I was using all GM pieces. However, the other 2 shops recommended to balance since it would see 7000 RPM's.
Taking it to a qualified shop helpes. IF your going that route, might as well do it on forged items. I know the crank is strong but why pay twice. I guess you can do it your way but I don't see you paying any less when reusing parts. Some cranks are easier to balance then others which should be stated.
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re balance it, otherwise start shopping for a new engine.
I went thru the exact same scenario you are going thru. switched from stock pistons to Mahle forged pistons. rotating assembly was supposed to be balanced when I took everything to the machine shop. It never happened and after 1k miles, I was pulling it back out of the car. wicked vibration, made no power and hammered every bearing inside the engine and destroyed the cylinder walls.
balance that engine or dont build it at all. it will not survive long.
I went thru the exact same scenario you are going thru. switched from stock pistons to Mahle forged pistons. rotating assembly was supposed to be balanced when I took everything to the machine shop. It never happened and after 1k miles, I was pulling it back out of the car. wicked vibration, made no power and hammered every bearing inside the engine and destroyed the cylinder walls.
balance that engine or dont build it at all. it will not survive long.
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Re-balance the assembly.
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If plan on running more than 6k rpm from time to time, then get it balanced.
If plan on running more than 6k rpm from time to time, then get it balanced.
Well the advice is overwhelming so it seems like a no brainer. Called my shop this morning and they charge $240. This engine is already becoming a money pit so what's another $240?
Launching!
Joined: Jul 2010
Posts: 238
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Definatly worth it, might be $240 but compared to what your paying in machining and other parts its worth it, the machine shop i went to told me to drop off my balancer and flexplate to do at the same time, they said its no extra so we can do it at same time, was a brand new under drive balance but needed a little bit taken out when balanced, gm flex plate was spot on how ever.
TECH Enthusiast
Joined: Nov 2017
Posts: 661
Likes: 91
From: S.F. East bay
what region do you live in. I'm in sf bay area and I'm just curious what I'm going to have to spend to get my lq4/ls2 balanced....240 is awesome u must be in Alabama or Tennessee. ....
Engine Balance Hi Dawgs, YES "matched weight" is most important.
I "over-balance" often with 1%-2% as common.
Your piston weight change is 8x of that value.
This Piston Pin has a weight of ???
You can increase that value ?
My Balance Shop charges $75.00 to "spin" the crankshaft with MATCHED items.
Lance
I "over-balance" often with 1%-2% as common.
Your piston weight change is 8x of that value.
This Piston Pin has a weight of ???
You can increase that value ?
My Balance Shop charges $75.00 to "spin" the crankshaft with MATCHED items.
Lance
