How to measure timing chain stretch?

[ryan1980]

Hi All,
I'm in the process of removing the sprocket that drives my noisy balance shaft on my VR V6... and before i remove my timing chain i want to know whether i should replace it or not.

How do you measure if it's stretched and how much is acceptable?

Ryan

[hako]

You hold the adjuster away from the chain and then move the chain and if the play exceeds 25.4mm it's time for a new one. On a high mileage motor, if it's not making a noise then I'd leave well enough alone.

[ryan1980]

Okay , it doesnt seem to be stretched so im gonna take your advise However i still need to remove it to get to the balance shaft sprocket.

In the manual it says to line up the timing marks, however i cant see any marks on the chain sprocket? Is it possible it's worn off?

Would i be correct in saying that as long as i take the chain off and put it back on in the exact same position, all will be wine? If so, i'll just mark it with some liquid paper etc...

[ryan1980]

Okay, found what i believe is the timing mark on the camshaft. Only problem is, no matter how much i rotate the engine, the 2 marks never line up. They come close, but never line up..

What does this mean and how do i fix it?

[GTP 85]

There are dots, almost like punch marks, on the cam gear and the crank gear. you have to look very carefully on the crank gear because it it very small and close to the teeth.

put the harmonic balancer bolt back in and rotate the crank so that the marks line up as close as possible. only then should you proceed to remove the cam gear bolt.

I strongly suggest that if you are going so far as to take the chain off, you may as well change the chain and gear kit. they are reasonably cheap for what you get. i just put a dual row in my v6 and cost about $120.

Not sure if you 100% know what you are doing, but i will tell you anyway. In the buicks the balance shaft bearings are splash fed so you can completely pull the shaft out. if your car is ecotec, best way to do it is pull the shaft right out, place it carefully in a vice and remove the gear on the end of the shaft. Very carefully slide it back in and refit the bracket that holds it.

DO NOT FORGET to put the camshaft to balance shaft drive gear back on before sliding the timing chain gear back on, as that gear has to be there to shim the cam gear correctly. Also make sure the dots match together

[ryan1980]

hmm my car's not ecotec , i was told that you can't remove the balance shaft... and to just remove the drive gear. So this is wrong?

[GTP 85]

my tuner/ mechanical mentor builds his own v6's and i sought his advice on the balance shaft stuff and he said with the buicks you can definitely pull the shaft out completely as the bearings are splash fed and you wont be bleeding oil pressure at the rear bearing, if removed. The ecotecs need a plug in the rear bearing if shaft is removed.

As i said, i just did this work on my VN S1 and i just hauled the whole shaft out, and added a dual row chain kit

[ryan1980]

Okay thanks mate. I'm at the stage where i've taken the chain off, sprocket off, and the balance shaft gear drive sprocket off... I also took the retainer off that , i thought, holds the balance shaft.

The balance shaft doesnt seem to want to come out. I would be happy enough if i could get the little sprocket on the end of the balance shaft off so i could stop it turning... but how the hell do you undo the bolt, if you can't stop it turning??

Thanks for all your help, as you can see, i dont reallly know what im doing! lol