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I 'd be suprised if a timing chain could stretch enough to make timing difference that would be greater than the variance of setting the timing.

I set mine with a snap-on oscilloscope to the book values and get around 15mpg on a run and occasionally nearly 18mpg. My truck exhaust does smell a bit rich but I suspect this is cats / O2 sensors rather than anything to do with timing.

Do you have any symptoms other than having read the internet? ;-)
 

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These engines can go well into 300 grand without any issues at all. Change the oil, keep up with tune ups and don't mash the gas a lot...you'll be good.
 

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I 'd be suprised if a timing chain could stretch enough to make timing difference that would be greater than the variance of setting the timing.

I set mine with a snap-on oscilloscope to the book values and get around 15mpg on a run and occasionally nearly 18mpg. My truck exhaust does smell a bit rich but I suspect this is cats / O2 sensors rather than anything to do with timing.

Do you have any symptoms other than having read the internet? ;-)
18mpg? Tell us your secret.
 

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18mpg? Tell us your secret.
Following Jimmy to Wintergreen from NYC to VA and back again I got almost 18mpg. I wasn't that close to be slip streaming but i was very surprised. The Oscilloscope was really cheap on craigslist ($150) and it does a great job of helping set the timing and seeing any other issues in the ignition system. You can even measure the spark gap to make sure it's right and it helped me diagnose a faulty lead that was causing me some major running issues in about 10mins of turning it on ... and I'd never used one before.

Snap-On Counselor MT1665 Digital Oscilloscope is what I have and it's perfect for the vintage of these trucks.
 

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mine was set way advanced at 15 degrees, and popping the check engine light after 15 min of running, i reset it back to factory spec (5 degrees) using my old the trusty craftsman timing light, and it runs great now.. fuel mileage "seems" to be up as well with that as the only change to fix the CEL. I did also install a new maxflow y-pipe but the same CEL issues persisted after that install, that was done to fix a rattling Right side Cat converter.
just keep it at factory Spec, make sure your putting enough oil in it after a change and keep it topped up, and do the regular maintenance, and you should be fine for many more miles to come.
Mine just turned 135k
 

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The timing chains do stretch, but I don't think this correlates to ignition timing. IMO, change the timing chain at that age. It really cuts into power and use a proper chain instead of the piece of crap that Rover supplies.
 

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Yes, the timing sets do wear and retard the cam timing, making the engine sluggish. I am also not a fan of the nylon timing gear, so I installed a Cloyes timing set. I do think the worn timing chain affects the ignition timing as the distro drives off the cam, but not sure if the chain tension reverses as the engine runs so if timed while running, you probably won't notice. If you have the timing cover off, your should replace the oil pump too - FWIW.
 

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Discussion Starter #9 (Edited)

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That is the only benefit of a nylon gear, although I am not sure I can hear any increased timing chain noise over the cacophony of other mechanical noise.
 
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