Timing chain/sprocket marks

[Don Starr]

*** EDIT: this was a dumb question. I answered it myself in post #4 in this thread

Greetings all-

I have a 2012 Liberty Jet 3.7L V6, 190k miles. Pulling heads to replace head gaskets.

I have the intake, valve covers, and timing cover removed. Looking at re-assembly instructions, the chains and sprockets have helpful markings to get the timing correct - plated links with yellow dots on the chains, yellow dots on the sprockets, L/R marks on cam sprockets, etc..

However, at present (before disassembly), none of the chain markings are where they're "supposed" to be. It's as if whoever was in there last didn't use the markings at all. The only markings that are "right" are the ones on the sprockets - they're all lined up / oriented perfectly when #1 is at TDC exhaust.

Is this something that might have happened at the factory? Or does it indicate that someone else has been in there before?

Edit to add photos:

 

[Don Starr]

It finally occurred to me that I don't know how many teeth are on the sprockets and how many links each chain has. Maybe I'll count them, but probably not. For now, I'll just presume that they might have been assembled "by the book", but end up looking wrong as soon as the engine turns just once.

 

[turblediesel]

Try turning the crank another 360° and see if your marks line up. Cams turn half as many times as the crank creating the 4 ****** cycle; ****, squeeze, **** and ****. (That's going to be censored!)

 

[Don Starr]

Turning the crank in increments of 360° didn't change the "weird" chain mark positioning. I did that multiple times when first locating TDC and then removing the rockers.

The marks on all of the sprockets (crank and both cams) line up perfectly relative to each other - and that's all that really matters for the valve timing.

It's only the chains whose marks don't line up with the "expected" markings on the sprockets.

... time passes ...

I've decided that my initial question was pretty dumb.

The marks on the chains are only there to aid assembly - to make sure you've got the valve timing correct - the chain marks don't matter once it's assembled. I counted teeth on the gears. Crank gear has 25, idler primary has 50, idler secondaries have 26, and cams have 26. Two rotations of crank give one rotation of idler, and one rotation of idler gives one rotation of cams. All as expected.

Number of links in chains will "mess up" the markings post-assembly, but that doesn't matter. In fact, it's almost guaranteed that the chain marks won't line up later - unless the number of links in the chains are some magic multiples of the gear tooth count, and even then only every Nth revolution.

 

[turblediesel]

Maybe it's a jeep thing to introduce ambiguity to valve timing. The CRD has camgear timing marks that are meaningless and it takes 3 full turns of the engine to bring the fuel pump timing marks into alignment with the other marks; all at 90° past TDC on the crank using the hidden crank mark.

At least the 3.7 doesn't use a rubber belt for the overhead cams.