V6 balance

[immortality]

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

On ecotec V6 engines, 3800 V6 engines are only splash lubricated.

[vlad01]

yep, and that is why the ecotec didn't have balance shaft bearing problems like pre ecotec did.

[vlad01]

Over the long weekend I pulled apart the engine I had in storage that somehow got water in the cylinders.

I wanted to get first had experience dealing with the timing set and balance shaft gears, bearing ect...

this engine made the classical buick crunchy rattle noise. Well I figured that would be bearings on the balance shaft for sure. Nope not even after 260k this engine showed the bearing being sooth and tight. spinning the balance shaft by itself was like butter.


instead I found the timing chain so loose that without the dampener it could almost jump a tooth. There was also a small amount of lash between the shaft gears. that in combo of slack chain I can see will cause the crunchy chattering noise as the gears change mesh from heel to toe when cam lobs go from ramp up to ramp down (load on the cam going from + to - as it rotates) there was almost equal wear on both heel and toe so that must mean load was going both ways

when I rock the gears back and forth hard the noise sound very much the same as what you hear when it runs.

So when I do the stuff on the VR I will check the front bearing for the balance shaft, most liking replace the gears, new roll master timing set and new dampener. When I had the intake off I checked for play in the bearings, was none that I could feel.

[Holden202T]

yeah im not surprised, they really should have put another 5mm in the timing cover and put a double row in them!

[vlad01]

what actually surprises me is the fact how long the front bearing lasts. given its only single row ball and runs at engine speed with the huge dynamic unbalanced load that placed on it.

yet all the Porsches from 95 to current with water cooled engine have catastrophic failures in less that 100k due to some single and double row ball bearings used in part of the valve train lol. They used to use a plain bearing in the air cooled era just before boxster and 996 came out.

just another testament to the buick design

[Holden202T]

umm, wouldn't it turn at half engine speed ?

and really i would have said theres bugger all load on it and the bearing in the front is pretty decent for what its doing!

but yeah no one can deny the buick is well designed!

[vlad01]

umm, wouldn't it turn at half engine speed ?

and really i would have said theres bugger all load on it and the bearing in the front is pretty decent for what its doing!

but yeah no one can deny the buick is well designed!

no its engine speed.

timing set brings the cam to half speed, balance shaft gears are 1:2 doubling the speed of the what the cam does thus back to engine speed but the main difference is its counter rotating, ie. counter clockwise to the engine.
In a inline 4 there are 2 rotating shafts counter and one non counter. They turn at 2x engine speed to fix a 2nd order harmonic vibration.


The force would be pretty big.

the radius of the shaft is about 30mm with each counter weight being at a guess 700-1Kg each half.

I have taken 750g as a figure to give you an idea. According to centrifugal calculators thats pulling 838Gs and at weight of 750g is 629Kg of force at each bearing as a ball park at 5000rpm.

by any standard, thats a lot!

just holding the shaft by the bearing and spinning it in your hand shakes your arm around just tuning it what might be 100rpm?




imagine the Gs on a turbo impeller! I worked out if the impeller is 100mm diameter, Have no idea what the standard size is these days. lets just say 100mm.

well at 150,000rpm its pulling over 1.2 million Gs! 1 gram out of balance its got over 1250kg force of unbalance. Some turbo can spool over 250k rpm.


And thats why I am surprised they last so long.

[Holden202T]

oh yeah i forgot the gear on the back of the cam is larger than the balance shaft gear!

[immortality]

what actually surprises me is the fact how long the front bearing lasts. given its only single row ball and runs at engine speed with the huge dynamic unbalanced load that placed on it.

yet all the Porsches from 95 to current with water cooled engine have catastrophic failures in less that 100k due to some single and double row ball bearings used in part of the valve train lol. They used to use a plain bearing in the air cooled era just before boxster and 996 came out.

just another testament to the buick design

I guess it depends on the end use of the bearing, I'd suggest that a porche engine sees a lot more RPM than the Buick does. Deep groove roller bearings will last for ever if they stay within there design parameters (max rpm) and get a good supply of clean oil etc.

Also, the problem with bearings in the valve train (particularly in rockers) is that the bearing motion is limited though a set arc rather than a full continues rotation of the bearing, this causes wear quickly and failure. The smaller the arc (less rotation of the roller element) the worse the problem gets.

It is amazing though some of the loads applied to bearings regardless.

I personally rip out or disable the balance shaft if the timing cover ever comes off.

[delcowizzid]

balance shaft belongs in one place the bin LOL or if doing ecotec and dont want to block the oil feed leave it in and no cog LOL. why keep something out of balance in there.ive even had cams balanced in a few builds for people