5.3 timing marks

[rockola1971]

I do not know where you read this is supposed to be done on the compression stroke. Alldatadiy.com which is the online version of the factory service manual, doesn’t mention anything about that. It just states to rotate the crank pulley until the mark is at 12:00 and then install the chain with the cam pulley at 6:00 and the dots lined up. Here’s a screenshot of that page. View attachment 381986

You dont have to do anything on the compression stroke. Its just easier to do it that way for the reasons I have listed. Plus if one of the rockers are tight while attempting to find #1 TDC then you are either not on #1 cylinder OR you are 360deg out. This method has been used for alot longer than ive been alive, especially for when the ignition distributor had to be rotated to adjust timing and adjusting ignition point gap before solid state ignition existed.

 

[MassHoe04]

With the gears for the cam and the crank being keyed or indexed to only go on the shafts one way, you could pull the gears and chain wherever the landed when the engine was shut down. As long as the cam and crank 100% absolutely do not budge... You can slap on new gears and chain in that same spot and be off and running. You may need/want to do a crank sensor re-learn, just to be sure. But, if nothing moved, you would be good to go.

It is the relative positions of the cam and crank that determines timing. If nothing moves, there is no change in timing, no matter what stroke it stoped on.

I was super-nervous the first timing set I replaced (my 05 Jeep 4.0L). but it was a lot easier than I thought it was going to be. I didn't have to do a thing once it was back together and it fired right up and ran like nothing happened.

 

[Rocket Man]

With the gears for the cam and the crank being keyed or indexed to only go on the shafts one way, you could pull the gears and chain wherever the landed when the engine was shut down. As long as the cam and crank 100% absolutely do not budge... You can slap on new gears and chain in that same spot and be off and running. You may need/want to do a crank sensor re-learn, just to be sure. But, if nothing moved, you would be good to go.

It is the relative positions of the cam and crank that determines timing. If nothing moves, there is no change in timing, no matter what stroke it stoped on.

I was super-nervous the first timing set I replaced (my 05 Jeep 4.0L). but it was a lot easier than I thought it was going to be. I didn't have to do a thing once it was back together and it fired right up and ran like nothing happened.

Why take the chance when the outcome could be serious damage? The cam is super easy to let move a tiny bit and then you’re screwed, even at one tooth off. So then you put it all back together including the harmonic damper which you don’t want to do twice and it won’t run or worse it does damage to the engine. The timing marks are there for this reason and its super easy to make sure they’re lined up. I don’t really believe in gambling with something like this, that makes no sense to me when it’s so easy to use the marks.

 

[MassHoe04]

You are right on that @Rocket Man .

Be careful in the process, do it right once.

I did line up the marks on the Jeep gears. I just did not stress on what stroke it was on at the time. I knew all would be good if the dots lined up before the gears came off and still lined up when they went back on.

 

[Rocket Man]

You are right on that @Rocket Man .

Be careful in the process, do it right once.

I did line up the marks on the Jeep gears. I just did not stress on what stroke it was on at the time. I knew all would be good if the dots lined up before the gears came off and still lined up when they went back on.

Yep, the service manual doesn’t say anything about compression or exhaust stroke, I’m not sure where the OP got that from.

 

[iamdub]

Yep, the service manual doesn’t say anything about compression or exhaust stroke, I’m not sure where the OP got that from.

This. With the heads off, how is one to know if compression or exhaust stroke? Yeah, you could look at the cam lobes and all that jazz, but it isn't necessary. I've never given it a second thought- just put the #1 piston at the top (not necessarily perfect TDC) and made sure the dot on the crank sprocket was at or near 12:00. With the chain hooked on the crank sprocket, I rotate the cam sprocket so that it's at 6:00 and I rotate it or the cam slightly as needed to get the cam sprocket bolted up. I have a pretty good eye for aligning the dots and can easily spot it if it's within a half a link off. No worries, just rotate the cam and/or cam sprocket accordingly and bolt it up. Then turn the crank a hair until the dots are aligned. The #1 piston will then automatically be at TDC and the system will be timed properly. Give it a couple spins and realign the dots to confirm, if that's what will give you the warm fuzzy feeling to proceed. The dots will only align properly with the #1 piston at TDC and it'll only be on the compression stroked due to the positioning of the cam lobes. This is why the cam sprocket has a locator dowel.

 

[djhoch83]

My 2006 Tahoe Z71 5.3 was running fine, but lost oil pressure. It’s been lower than my 02 Tahoe, but it suddenly dropped while idling. I opened it up to replace that stupid O ring at the top of the pickup tube and the oil pump, and decided the timing chain needed to be replaced as well.

I haven’t removed the chain yet, because when I set the #1 piston to TDC on the compression stroke, the timing marks were both at 12:00, not 6:00 on the cam and 12:00 on the crank (pointing at each other) as the manual says they should be. Since the engine was running fine, I’m assuming I should put it back that way, but I don’t know if there’s a reason I should move it 180° to point the marks at each other. Has anyone else found this to be the case?

I’ve only had this truck for about 20k miles and 6 months. My ‘02 is at 554k and needs a rebuild soon, so this is the replacement for now and I don’t have a lot of history on it. The guy I bought it from does specialty engine rebuilding and LS swaps for hot rods but said he had never done anything to this truck other than drain all the fluids as soon as he got it. I don’t have any history prior to that, but it’s in good shape with under 200k so I doubt the timing chain has been done before.

Hey Ken I’m having the same issue with my ‘16 Yukon. 1# piston is up and valve are up but indicators are 180 off. With cylinder one still up tdc I took the pressure off the rockers, took the chain off. Rotated the cam to line up the marks (cam 6 crank 12 o’clock). Put everything back together rotated with the pressure gauge in #1 plug hole. Its still coming up 180 off. Just wondering what your outcome was. Thanks in advance

 

[Rocket Man]

Hey Ken I’m having the same issue with my ‘16 Yukon. 1# piston is up and valve are up but indicators are 180 off. With cylinder one still up tdc I took the pressure off the rockers, took the chain off. Rotated the cam to line up the marks (cam 6 crank 12 o’clock). Put everything back together rotated with the pressure gauge in #1 plug hole. Its still coming up 180 off. Just wondering what your outcome was. Thanks in advance

Read The whole thread. Put your pressure gauge away and simply line up the dots on your crank and cam. Nothing in the service manual says anything about compression or exhaust stroke. You can read the section in this link relating to cam install. And verify afterwards by turning the engine over by hand to see there’s no interference and the dots still line up. I’ve done 3 cam installs in LS engines this way.

LS1Howto.com

 

[nonickatall]

There is nothing in the description about compression stroke, because you are automatically in the compression stroke, when the two marks are in line with each other, i.e. the crankshaft is at 12 o'clock and the camshaft is at 6 o'clock.

And that's all you need to know.

It's also right, that it's best to do this in this position and that only for one reason:

Because you see if your timing is correct.

It's of course also right that you can change the timing chain at any position, if you put it back on without moving crank and camshaft but may be, the camshaft twists a bit, due to the tension of the valve springs and you then no longer know which tooth is exactly the right point.

So it is best to turn the engine to the appropriate marks to take the timing chain down and reassemble the timing chain back on and then crank the engine once, which means you have to turn the crankshaft twice.

Then the marks are back in the right place and must match. Manual cranking also prevents mechanical damage generated if the timing chain is not placed correctly, because you notice when the piston hits the valves without making damage.

When you do that with the starter, you notice it as well. But then you have to check the manual for the section engine swap.

That's why you should crank the engine twice by hand. Two crankshaft rotation, check. Two rotations again, check again.

If the markings are still correct, then everything is fine and you can reassemble the engine.

At the LS engines that is as simple as it can be. If you see some German engines from BMW or Porsche.

In a V8 with 4 camshafts, they sometimes have several balancing shafts and a high-pressure injection pump that has to be also lined, plus a chain tensioner. Then it becomes really difficult and usually only to do with setting tools.

I never in my mechanic life, saw a timing chain which is so simple like on the LS...

 

[nonickatall]

Here an example.. An Audi 3Liter TFSI.

A Pain in the A....