Balance Shafts

[jb300zx]

Alrighty then! Gonna start the controversy thread here. Viewpoints on the elimination of the infamous, potentially engine killing, balance shafts. I know, I know. "there are other threads on that". Just want to add to the informational value of the site here in the only thread I can access at this point. Not looking to make a decision here. My decision has been made. I, being a machinist, have already machined and re-balanced my rear shaft while removing the front one alltogether. I like the extra support this approach provides to the oil pump gear. Here is my thought. The driven gear has a front and rear support surface on the shaft. The opposite gear, however, has only one point of support once an "elimination kit stub shaft" is installed. This causes the gear to "sideshift" over time thereby eating up the pump case and possibly thrashing an engine. I see this as being a problem even with the OEM stub shaft. In support of my point of view, let's realize that the factory covered up the balance shaft issue by creating another one in my honest opinion. What are your thoughts on balance shaft elimination? Please support your theories. This is, after all, the newbie forum, and many newbies are gonna be considering this modification. Thanks, in advance, for the thoughts on this modification.

 

[XiKeiyaZI]

This should likely be merged with the other countless posts about Balance Shaft Eliminations. My 2G is running a 6-bolt swap and has a BSE done. I honestly couldn't tell the difference when I started driving it. Car runs perfect without any extra vibration, really.

 

[jerzeeog]

You got a good point there, though I'm not 100% sure what you're saying is completely correct. As far as I'm aware the b-belt was there only to reduce vibrations and when it's replaced with the stub it doesn't do anything in regards to engine function/reliability.

What I am looking to do is remove the B-shaft and add a harmonic balancer to compensate for the vibrations.

 

[jb300zx]

You got a good point there, though I'm not 100% sure what you're saying is completely correct. As far as I'm aware the b-belt was there only to reduce vibrations and when it's replaced with the stub it doesn't do anything in regards to engine function/reliability.

What I am looking to do is remove the B-shaft and add a harmonic balancer to compensate for the vibrations.

You're on the right track. No need for a secondary harmonic balancer. The crank already has one. The only thing the balance shafts do is eliminate the "felt" vibrations inherent to the harmonics of the four cylinder engine due to how it fires and rotates. The stub shaft does it's job, but not without some risk. Not saying it will result in immediate engine failure(on a daily driver). I am referring to long term on a daily driver. The trimmed rear shaft option eliminates the possibility of the stub shaft allowing the gear to walk. In addition, it is just as, if not more, cost effective than buying an elimination kit with a stub shaft. Any machine shop worth it's wieght could modify the shaft for a minimal charge. Thanks for the reply.

 

[turbo tim1]

I don't see how what your saying can happen because there is almost no load on the stub shaft, but when there is a heavy weight attached to it making it spin out of round I could see the balance shaft doing the damage before the stub.

I have driven on deleted balance shafts for over 60 000 miles before I rebuilt my engine, when I took my pump apart for inspection, there was no abnormal signs of wear, just the left over scratches from when the balance shaft was there. Those scratches were there the first time it was apart to remove the shaft, I assume this was from the weight causing the shaft to walk around a bit.

You have to remember these shafts spin twice as fast as the crank shaft.
I remember talking to my local machinist about this and he was telling me if I Removed them I would have certain engine failure in the near future, needless to say I never did.

 

[jb300zx]

I don't see how what your saying can happen because there is almost no load on the stub shaft, but when there is a heavy weight attached to it making it spin out of round I could see the balance shaft doing the damage before the stub.

I have driven on deleted balance shafts for over 60 000 miles before I rebuilt my engine, when I took my pump apart for inspection, there was no abnormal signs of wear, just the left over scratches from when the balance shaft was there. Those scratches were there the first time it was apart to remove the shaft, I assume this was from the weight causing the shaft to walk around a bit.

You have to remember these shafts spin twice as fast as the crank shaft.
I remember talking to my local machinist about this and he was telling me if I Removed them I would have certain engine failure in the near future, needless to say I never did.

Please understand I am not talking about running the stock shaft which is naturally unblalnced, but a stock shaft machined to a balanced state on the rear/pump gear side. Not just machined, but machined round and then balanced so as to eliminate the wear marks you speak of. Best of both worlds. A balanced shaft spinning in an oil lubed bearing that also provides extra support to the oil pump gear. Necessary, maybe not. Cheap insurance, oh yeah. Cost to perform this mod, minimal. Not disagreeing with you, just elaborating on my view. You make a valid point as to the reliability of other elimination methods. Thanks for your input.

 

[turbo tim1]

Mine wasn't a kit, I deleted it my self, tapped it, put a bolt in with thread locker and reinstalled it.

 

[jb300zx]

Mine wasn't a kit, I deleted it my self, tapped it, put a bolt in with thread locker and reinstalled it.

Nice. Glad to know that trick worked. I was curious about that one. Good to know. Thanks again.