Balance shafts /crank

[silicosys4]

I"ve been searching for a while and haven't found any answers to my question, which is probably answer in itself but i'll still ask.

When you remove your balance shafts do you have to have the crank balanced?

A buddy of mine who fancies himself to be something of an authority on dsm's has insisted that if I'm deleting my balance shafts that I HAVE to get my crank balanced, and that any reputable shop won't do a balance shaft delete unless they are balancing my crank at the same time or know its balanced.
I have heard nor read anything that suggests he is correct, and I'd like to hear from others if they have heard or experienced anything to confirm or deny this.

 

[2GbTalonGuy]

No you don't have to balance your crank doing a BSE. The correct name for the balance shafts is "Silence shafts". They *mask* vibrations in the engine. Then in no way balance anything in the engine.

Tell your friend he is an idiot.

 

[and1chewy]

No you don't have to balance your crank doing a BSE. The correct name for the balance shafts is "Silence shafts". They *mask* vibrations in the engine. Then in no way balance anything in the engine.

Tell your friend he is an idiot.

agreed the balance shaft and the crank as its writen in your title are two separte things. only reason to get a crank balance is if your rebuilding the motor or buying a new crank (never hurts for the relatively low cost at the machine shop).

 

[silicosys4]

Yea I figured that the motion of the crank isn't going to be affected by the balance shafts, but that the vibrations caused by said movement would. I plan on getting the crank balanced at some point, but that is going to be a project in itself, and will involve new pistons/rods/bearings, in prep for 8.5k+ rpm's and something approaching serious power.

 

[TunaTalon]

Like others have said above. Except there is no profit in telling your idiot friend that he's an idiot.

The balance shafts compensate for differences in velocities of pistons going up from pistons going down. The differences cause a vibration that is two times the period of the crankshaft rotation. If the crank is out of static balance it will cause vibration at the period of rotation. Neither of the two periods can affect the other.

Still get the crank balanced on the next engine rebuild, just don't use the balance shafts as a reason.

 

[2GbTalonGuy]

Like others have said above. Except there is no profit in telling your idiot friend that he's an idiot.

Oh come on, you know it would be deeply satisfying.

 

[silicosys4]

It would actually be very satisfying. He's a good guy, but for someone who has never owned a dsm, he sure does "know" a lot of things about them, 95% of which is true, 5% of which you'd never be able to convince him is wrong.

 

[MichaelSuch]

I balanced my crank when I switched to the 100mm crank so my engine was stroked to a 2.3. There was a noticeable difference when the 2.0 didn't have balance shafts and the rotating assembly was not balanced compared the 2.3 crank now. the 2.3 still has a little vibration, but the machinist didn't take much material off. I would recommend getting it balanced if you want a smoother ride.

 

[fast90eclipse]

Hey how hard is it to do a bse ### I've heard its a nightmare to do with the motor still in the car. I wanna get it done?

 

[2GbTalonGuy]

Hey how hard is it to do a bse ### I've heard its a nightmare to do with the motor still in the car. I wanna get it done?

I just completed my BSE with the engine out of the car, and it wasnt hard at all. I think the hardest part about doing the install with the engine in the car would be removing the front shaft bearings.

Here is a good write up:
http://vfaq.com/mods/balance-shafts.html

 

[and1chewy]

Yea I figured that the motion of the crank isn't going to be affected by the balance shafts, but that the vibrations caused by said movement would. I plan on getting the crank balanced at some point, but that is going to be a project in itself, and will involve new pistons/rods/bearings, in prep for 8.5k+ rpm's and something approaching serious power.

just a suggestion but when you get to that point i would give my machine shop everything i planned on putting in your car. In a perfect world everything comes outta the box ready to use but in reality this is not the case.