Checking Timing Chain for stretch

[vernj4]

Is there a way of checking the timing change without removing the cover?

[britannic]

Remove the oil filler pipe, turn the crankshaft damper backward a revolution and set the timing mark at the 12 degree (or the last degree mark counter clockwise). Now watch the IP driven gear whilst slowly turning the crankshaft clockwise. As soon as you see movement, stop rotating and check to see how many degrees the damper moved - you should probably replace the chain if the there was more than 4 degrees of rotation.

[StephenA]

How advantageous is the timing gear upgrade instead of the chain? I read something about putting them in when changing out the water pump?

[Turbine Doc]

Any service shop with a Snap on MT2500 scanner or GM tech 2 can look at timing actual vs desired if more than 1.5 deg on avg delta between the 2 you need to be putting away some coin for the swap. Gears vs chain your call how deep is your wallet, modern double roller set are a good replacement option, that said gears have gotten good press and service reported on the power project truck on the page, do a search if those threads did not get wiped out a lot of pro & con discussion on that topic, one of those calls you will have to make which is best option for you.

[rlvelin]

I just installed the timing gears last weekend on my '93 6.5TD with 190,000 miles. The chain I removed had at least 3/4" of deflection in either direction (measured with the calibrated eyeball) and to make up for this slack the IP timing was advanced about 1/4" from scribe mark (don't know how many degrees this would translate to). IP timing is now at scribe mark and seems to perform better than previous condition.

Although the engine is a little low on compression and has some blowby my observations were there is definetly an improvement in throttle responce, less engine overrun during deceleration and more fuel efficiency as indicated by less black smoke during hard acceleration and less white smoke when cold, mostly due to low compression & blowby, but also contributed to by out of sync valve timing.

I chose the gears over the chain because a chain will always stretch out again even if a good quality prestretched chain is used (which I couldn't find) although to a lesser degree. The price on the chain set was around $120 and the gears were DSG for $250 from Kennedy. I could theoretically rebuild the engine 100 times and not have to replace the timing set. It makes sense economically if you plan on using the engine more than the expected life of one chain set or if you don't want to deal with the IP timing compensation due to a stretching chain. By the time you need to replace the timing chain set again you'll have spent more money (gasket sets add about $15-$20 each time) and done twice the labor.

If you ever get as far as removing the water pump then you might as well change the timing set if it needs it. I removed the radiator when I did mine which only added about 5 min to the project. That allows more room for the pullers and other variuos tools and you aren't smashing all the cooling fins as well as adding so many bloody knuckles to the mix. Plus all the junk that collects between the radiator and condensor can be clean out and you can pressure wash the radiator if need be.

Anyhow just wanted to contribute some info that could help you make the decision, but basically it comes down to how much $ you want or can afford to spend at one time vs. the long run. By the way I cannot hear the gears over the diesel noise unless I remove the oil fill cap but the white smoke that is emmitted when I do reminds me of the upcoming rebuild so I don't do it very much.
Hope this wordy reply helps