V6 balance

[vlad01]

I have been reading up on V6 balance, particular they 90º V6.


My understanding is the rotating mass is normally statically balanced but can not be fully dynamically balanced due to each bank having odd number of cylinders, like 2 inline 3s joined at the crank.

Most of it is offset via large counterweights at the ends of the crank, split crank pins for even fire for the 90 and 60º engines

So a counter rotating balance shaft is used to offset any remaining primary imbalance.

I have also noted for a while that our V6s use external balance, I am not sure on the reason, perhaps there isn't enough room to add the counter weight size required for full internal balance. Anyone got any info on this?

Naturally, the balance shaft can be removed? anyone got direct experience with this? I assume to then allows for a rocking N-S direction at lower RPM? I guess like that harsh vibration you get in a VN series 1 at low RPM

From my understanding and from some experience there is many external counterweight sizes and also different balance shafts.

here is some info.

http://en.wikipedia.org/wiki/V6_engine# ... smoothness

[immortality]

I took the balance shaft out of my VN (s1) and fitted a Powerbond race balancer and I'd say it is smoother now than it ever was with the standard balancer/balance shaft. Fitting the Powerbond balancer also got rid of a nasty vibration @ approx 2500rpm that the car always had.

The stock balance is a POS.

[vlad01]

yeah, I reckon thats the problem in my VP, there are pretty bad vibrations at certain RPM that din't exist when i got the engine. I noticed the harmonic balancer on it wobbles like spastic at those said rpm.

So, would you advise me ripping out the balance shaft on the new VR plus new power bond. Do I have to get the power bond mirror balanced to the old one?

My balance shaft is making a slight rattle noise guaranteed caused by slow granny driving that it did, since they are splash feed.

if you don't frequently take them to higher rpm those gears and bearings never get enough oil. My vp has been hammered from day one I got that engine. the balance shaft is silent, but everything else is worn lol. I found they only get oil once the valley is flooded with high enough oil level to actually run into the bearings.

Anyway, rather than sourcing all the parts for the balance shaft reco it will be cheaper for removal

was there any gain in performance as well?

[Dazza92VP]

you can run the double row timing chain as well with the shaft removed. as for the balancing you have to quote your engine number to whom ever your buying it from due to different balances just for different dates the engines were manufactured and thats about all you can do

[antus]

Back in the late 90s my mate had a vp was it sv6 with fe2 suspension and a t5? He put a capa supercharger kit on it and this was my introduction to delco ecus. Anyway he had the engine rebuilt and balanced, and the mechanic suggested to omit the balance shaft and expect it to be a bit rougher. He did but the results were fantastic. It suprised all of us by being very smooth and was a pearler of an engine. So I would suggest a balance, remove it and dont replace it. Ive seen it work first hand.

[delcowizzid]

i pull the balance shaft out of every engine i do theres 4 or 5 different ones.theres 3-5 different baancers depending on which engine series.its easy to see by looking at the rear of the balancer theres a counterweight and they are all different lengths.v6's if balanced should be balanced to 33.3 % or there abouts i have the exact figure somewhere.if you want to rev it theres a different balance amount that will smooth high rpm but give you rough idle.and if you solid mount 1 you neeed to just experiment and balance to the point it doesnt wipe main bearings

[festy]

The Bosch Automotive Handbook covers engine forces and balancing for different cylinder configurations in reasonable detail, I can probably scan the relevant pages if you want?

[delcowizzid]

buick power source manual is a good book on the subject of v6's

[vlad01]

I don't plan to do any balancing, so would it be safe long term without the shaft?

[charlay86]

Yeah should be fine to pull out, the only thing to remember to plug the oil holes.