6.2 and how much Timing Chain Slack or stretch is “normal” ?

[Jake59]

Good evening all,

Been trying to determine the amount of stretch my timing chain has and with only 25000 miles on this M1009, my findings are of concern to say the least.

I found the slack to allow between 7 and 9 degrees of crankshaft rotation before the valve train is engaged.
This really sounds like a lot, considering the low mileage on this M1009; that is assuming the tachometer is correct...

On the other hand, having lived military life for 36 years, I know how often vehicles are left idling for extended periods to assure batteries stay charged and radios can be operated.
This puts limited mileage on the instrument panel but the total engine operating hours increase considerably.

Just wondering if extended idling - or operating at creep speed - could cause such (excessive?) chain stretch ?
And, how many degrees slack is “normal” or acceptable before timing set replacement is recommended ?

Thank you,
Jake

 

[Tailwheel]

I just changed my timing chain. It had around 0.80"-1.00" slack, the max or just beyond the max allowable limit with only 50,000 miles. The new Cloyes chain has around 0.40" slack.

Directly from the TM 9-2320-289-34 Intermediate Support, 3-33:

1. Mount dial indicator to front of engine block . Position dial indicator plunger so that it contacts timing chain (4) midway between camshaft sprocket and crankshaft sprocket. NOTE When moving timing chain to check free play, ensure that it is moved parallel to front face of engine block.

2. Applying finger pressure on inside of timing chain, move timing chain outward as far as it will go. With timing chain in maximum outward position, set dial indicator to “O.”

3. Applying finger pressure on outside of timing chain, move timing chain inward as far as it will go. With timing chain in maximum inward position, note dial indicator reading

4. Maximum free play with used timing chain must not exceed 0.80 in. Maximum free play with new timing chain must not exceed 0.50 in. If free play exceeds this limit, replace timing chain and sprocket

 

[Jake59]

I just changed my timing chain. It had around 0.80"-1.00" slack, the max or just beyond the max allowable limit with only 50,000 miles. The new Cloyes chain has around 0.40" slack.

Directly from the TM 9-2320-289-34 Intermediate Support, 3-33:

1. Mount dial indicator to front of engine block . Position dial indicator plunger so that it contacts timing chain (4) midway between camshaft sprocket and crankshaft sprocket. NOTE When moving timing chain to check free play, ensure that it is moved parallel to front face of engine block.

2. Applying finger pressure on inside of timing chain, move timing chain outward as far as it will go. With timing chain in maximum outward position, set dial indicator to “O.”

3. Applying finger pressure on outside of timing chain, move timing chain inward as far as it will go. With timing chain in maximum inward position, note dial indicator reading

4. Maximum free play with used timing chain must not exceed 0.80 in. Maximum free play with new timing chain must not exceed 0.50 in. If free play exceeds this limit, replace timing chain and sprocket

Hi Tailwheel,

Thank you, much appreciated.
A pity there are no values in degrees crankshaft rotation to go by, which would allow for checking without having to open up the front end.
Guess I will have to remove the front cover then to take some measurements, but I am almost certain chain stretch will be out of tolerance...

Cloyes or Melling timing set, which do you recommend ?

Thank you again for your reply and help.

Jake

 

[Tailwheel]

Hi Tailwheel,

Thank you, much appreciated.
A pity there are no values in degrees crankshaft rotation to go by, which would allow for checking without having to open up the front end.
Guess I will have to remove the front cover then to take some measurements, but I am almost certain chain stretch will be out of tolerance...

Cloyes or Melling timing set, which do you recommend ?

Thank you again for your reply and help.

Jake

I only have experience with the Cloyes, reputable brand and mine went right on. Getting the old crankshaft sprocket off did require a puller, it was a tight fit on the woodruff but it didn't put up too much of a fight. The new parts slid right on. I just installed Melling's high volume oil pump too, seems like a nice unit but I have no way to tell how much of a difference it made, if any.

 

[Skinny]

Time is money

If you are far enough in to measure the chain stretch you should be replacing it anyway.

I could understand if this was a V engine with overhead cams but what is a chain for 6.2 like under $150?

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[Tailwheel]

Time is money

If you are far enough in to measure the chain stretch you should be replacing it anyway.

I could understand if this was a V engine with overhead cams but what is a chain for 6.2 like under $150?

Sent from my Moto G (5) Plus using Tapatalk

$70.59 with free 1-day shipping through Amazon prime.

 

[Skinny]

Yup, I wouldn't even breakout a dial indicator for that kind of money.

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[Keith_J]

You inspect when you have it apart. You know it should be replaced when the chain slaps the cover. You can hear it.

 

[Jake59]

Hi All,

Thanks for the advice!
Ordered Cloyes Timing Set and Fel-Pro Gasket kit.
Another M1009 To Do Item on my list...

Cheers,
Jake