Putting balance shafts back in??

[DSM Jeff]

Ok I'm debating on putting balance shafts back in an engine for my fathers car. I'm in the process of building my father his 2nd DSM and my old/new engine will be going into it. I had removed the balance shafts and am considering putting them back in or putting brand new ones back in to reduce vibration in the car. I'm also staying with rubber mounts.

I'm just wondering if anyone can see any ill affects of putting balance shafts back in an engine. I would obviously install new bearings. But I'm trying to understand what causes the shafts to break or seize? Should I go with new shafts from the dealership? The rotating assembly was balanced when it was built.

You may think I'm crazy but this is going to be more of a stock car, small 16g, small fmic, fuel mods, 2.5" exhaust. Just something fun for my old man with comfort in mind. My car has no balance shafts, poly engine mounts as well as poly subframe bushings and vibrations travel through the whole car. He's not going to care for that.

Thanks.

 

[turboglenn]

I'm not sure what causes them to sieze up.. But i see nothing wrong with running b-shafts at all honestly, the only real reason i run without them is so the bs belt doesn't act like a grenade to the timing belt should it go out.

what's weird is i pulled the rear shaft from my motor and left the front one in with no belt on it and last time i had the timing cover off the front shaft was frozen in place, i could not turn it by hand, and i never tried with a wrench but it was puzzling to say the least.

 

[Grimis]

I had my motor out in 05, and i had them in my hand and i put them back in , and 400miles later the rear one locks up and takes my oil pump out. So if you got them in your hand leave them out. BSE kits run $45esh, better then having the engine rebuilt. just my .02$

 

[VETTE_50_TH]

Like most things, lack of lubrication. It only takes one time to lock up and your rebuilding that motor again. Also, it adds more weight to the car, as if these cars arent already heavy, it adds more rotating mass to the oil pump, making it less efficient, and more likely to break something becuase they are there. All those reasons make it an undoubtedly easy decision. If you are sticking to rubber mounts, i think that will be more than enough to keep the car from violently shaking for your old man.

James

 

[DSM Jeff]

I'm really on the fence about this. Its around $300 for new shafts alone, then bearings and new gaskets. I think I will leave them out and hope the rubber mounts keep things smooth enough. Hell I bought my car with a blown engine due to the balance shaft breaking.
I'll tell the old man he'll have to deal with it
Thanks.

 

[TunaTalon]

BS bearings fail because they are heavily loaded due to the imbalance of the shafts. The main bearings on my Talon were "like new" after 183,000 miles bathed in Mobile One while the balance shaft bearings were worn near end of life.

Getting more horsepower with the shafts removed is somewhere between lore and myth. Without the balance shafts the engine vibrates enough to shake the whole car. However much horsepower it takes to keep that vibration going is how much less horsepower is available at the crank.

To us olde folk who grew up driving smooth revving V8s a shaking engine is annoying and even feels "expensive".

 

[nikkeebabee]

Leave them out...With the rubber mounts in the car vibration is not bad at all... Why risk having a shaft seize and take out the timing belt...

On top of which by blocking it off it will keep the oil pressure up which in most cases (not all) is good...

 

[DSM Jeff]

See I've never had a car with rubber mounts and no shafts. Only no shafts and poly or a stock car. I'm going to leave them out and buy new rubber mounts and see how it feels. Worst case is I put shafts back in.
Thanks for the positive responses, I was wondering if I was going to get people saying its dumb to have them.

 

[matthewdesigns]

I'm having a motor built right now for my DD, and I decided to leave them in. I'm going to use a kevlar bs belt for some extra protection, though.