What the balance shaft does

[14secvp]

some info maynot be valid but gives an idea of why its even there


BALANCE SHAFTS
Any 90° V6 creates some strong, primary imbalance forces, especially in the vertical mode. The 262 is no exception. Chevy originally underbalanced these engines by putting about 46% on the bobweights instead of the usual 50%. This reduced the vertical imbalance that was trying to lift the engine up off the mounts, but created a strong horizontal imbalance that shook the engine from side-to-side instead. So, in order to eliminate a lot of the "noise, vibration and harshness" in the engine and make it into a world-class motor, Chevy added a balance shaft to the premium engines in ’92 and included it in all of them by ’95.

There are two balance shafts, a light one and a heavy one, and two versions of the light one. See photo. The light one is either a 10224542 or a 10172748 casting that comes with or without a metal wear sleeve installed on the back journal, depending on the application. The wear sleeve was used on the lightweight balance shaft when it was installed in a ’92 "first design" engine with the needle bearings in the back, but it wasn’t used when the lightweight shaft was installed in the "second design" engine that had a bushing in the back of the block.

This "first design" shaft should not be used in a "second design" engine because the wear sleeve shortens the surface area needed for the bushing. These lightweight shafts were installed in all of the engines that had the light pistons including the ’92-’98 VIN "W," the ’96-’98 VIN "X" engines and the "first design" VIN "Z" engines in ’95 that were built with the lightweight pistons.


The heavy balance shaft is either a 10224541, a 10105902 or a 12550286 casting. It can be visually identified by the raised identification band around the middle of the shaft. It was used in all the ’93-’94 VIN "Z" balancer engines and in the ’95 "second design" VIN "Z" balancer engines with the heavy pistons. The heavy balance shaft weighs about 125 grams more than the light one, so it shouldn’t be interchanged with the lighter one.

The balance shafts rotate at engine speed and are gear driven off the front of the cam. There are two different gear sets, one with "wide" teeth and one with "narrow" teeth. The ones with the "wide" teeth were used in the "first design" engines along with the needle bearing balance shaft. Some of these early balance shaft engines had a whine to them, so the gears were modified at the same time the block was changed over to the "second design" version with the sleeve bearing in the back. We recommend using only the "second design" gears to help avoid any possible noise problems.

[HIROLLA]

So what should the engine be balanced at without the shafts and with a double row timing chain?

[14secvp]

from what ive been reading it doesnt matter how you balance it there seems to be a nasty harmonic vibration that people have been experiancing at lower revs people with bigger cams dont so much notice it heres a few threads on the subject
http://forum.****************.com.au...p/t-13597.html
http://forum.****************.com.au...p/t-20746.html

hope I dont get in trouble for posting sc forum stuff do a search under buick 3800 balance shaft removal with google theres heaps about the whole subject

[PaRaDoX]

you know i noticed something strange when pulling my motors apart... the vp balance shaft is heaps diffrent to the vn s1 balance shaft

[14secvp]

does the s2 one look like a bigger heavier balance shaft with bigger counterweights or lighter smaller shaft with smaller counterweights any casting numbers or you allready got your manifold on

[Rhino Racing]

Good info Spanners . It explains a lot.
Some speedway divisions remove the balance shafts and have the double row timing chain instead.( i can't in my division)
But yeah i have noticed that at lower revs some of them seem to be a bit shaky, but under revs and/or load this does not seem to be there.
I guess when it comes to comfort, vibration is not an issue for these cars ..... and the engines are usually stripped every season and checked out for wear and damage.
Keep up the good work!

[cxcxcxvcvcvc]

this would probably explain why my old vn pushed 3 lifters sideways snapped of one of my rocker assemblys and hydraulicaly locked the motor: $1500 later saw her back on the road i have heard that this was a common problem in earlier model v6s as the heat generated (and age of the motor) can cause the cam to weaken misalign and get a slight wobble and cause the above mentioned some mechanics i have spoken to reckon this is a problem around the 180xxx mark wich is roughly where mine was when this happened. by the way good write up mate

[14secvp]

least it gives people an idea on how and why its there before they rip it out

[bpefi]

this would probably explain why my old vn pushed 3 lifters sideways snapped of one of my rocker assemblys and hydraulicaly locked the motor: $1500 later saw her back on the road i have heard that this was a common problem in earlier model v6s as the heat generated (and age of the motor) can cause the cam to weaken misalign and get a slight wobble and cause the above mentioned some mechanics i have spoken to reckon this is a problem around the 180xxx mark wich is roughly where mine was when this happened. by the way good write up mate

A lot of the earlier v6 motors had problems with alignment of the journals for the cam as they where not done properly from the factory - std fix is to bore them out properly

[acarmody]

Also an epic thread dig.