Timing Chain Stretch Issue

[stepper]

Here's where is stands. My learning curve never ends! I took the check valve out of my compression test adapter for the 616 engine and connected it to a length of clear hose. As stated in the test procedure, I could see the bubbles leaving, and then the liquid rise in the tube. But, the meniscus of the liquid would immediately return the liquid level in the bottle, before any marks on the tube could be made. This told me I have a leak somewhere.

My earlier compression test of the cylinder proved out at 460 PSI.

I removed the adapter and tested it for leaks... it's good.

I backed off both valves adjustment so the valve stems were completely clear of the rocker arms in the rotation area of TDC. Test still showed signs of leak.

I applied 15 PSI air pressure the to the (bottle) end of the clear hose and could hear air leaking inside the engine, with both valves closed. I applied leak detect solution around the pre-combustion camber and the glow plug insert, no air leak visible. I slowly turn the crank until I could minimize the air flow sound. Around 4° BTDC the sound was barely audible, then around 6° ATDC the air flow sound was back.

I switched the adapter to #2 cylinder to see if it behaved similar to #1 cylinder. Positioning the cam shaft so both valve were closed, I could hear air leaking also.

I'm not sure where the air bypass is coming from, I'm assuming the rings. Until I can come up with a solution, the cylinder leak is preventing me from determining TDC for cylinder #1.

I can see the transition from bubbles to suction, but when I relieve the torque on the crank my reading disappears back to bottle level.

Anyone have understanding as to why the air is leaking in the cylinder?

[Sugar Bear]

Rings never seal perfectly, even when new and fully seated there is some leakage at least at the end gap. As the engine wears the leakage worsens when the piston goes up in the cylinder due to cylinder wall taper from wear.

[Sugar Bear]

Interesting method your using, I've not done that. Keep us posted.

[engatwork]

Blowby?

[stepper]

Here's where I'm at in my testing. What do you think, new chain or Woodruff key?

https://www.youtube.com/watch?v=oBTKeACibz0

[Sugar Bear]

My vote is for a new chain. FWIW, I've seen a few of those engines break chains with zero warning.

[stepper]

I'm back. Got the new timing chain installed. Some weird occurrences happened and any explanation would be appreciated.

Issue 1: As I was rotating the crank, with the chain securely ty-wrapped in four places, the chain in the tensioner area would suddenly go very slack. Then a few more degrees rotation of the crank the chain would tighten up again. Why?

Issue 2: I started the chain pull at TDC. The pull ended at 65° BTDC, neither is the cam mark matched @TDC. I freaked at first, thinking I should end up where I started... Someone please tell me this is not an issue?

Haven't pressed the master link yet, it is on hold until I get Issue 2 understood.

[Sugar Bear]

I can't explain what happened but the cam and crank must be aligned i.e, crank at 0 and cam marks aligned. If that is the case I wouldn't be concerned about it ending at 65 degrees.

Was the chain kept taught completely through the "roll in", never slackened?

[engatwork]

Can you put crank at TDC?

[stepper]

I did keep the new chain tight. The old one coming out was tywrapped to the cam gear also. That's when I noticed the slack, then kept it tight with my fingers pushing it in while I turned the engine over. I guess I should have been pulling on the old chain. At the time I started rotating the engine the old chain was tight being tywrapped to the cam. I'll press the new link on tomorrow and rotate the engine (by hand) a few times before I check the TDC, keeping my fingers crossed.

[Sugar Bear]

If you encounter resistance stop, it would be a valve hitting a piston depending upon if it is out of valve time. The valves are robust and not on an angle so it is pretty tough to bend a valve.

[stepper]

Okay, I had ordered a temporary master link and installed it in order to check the timing marks. With the balancer set at TDC the cam mark was slightly off. With the cam mark centered the balancer is at 5° ATDC, exactly what I had prior to rolling in a new timing chain. My understanding is the cam gearing is 18° difference between cogs (teeth), so the chain isn't off by one cog. So, I've essentially accomplished zip, other than to learn how to roll and new chain in.

I have noticed the cam shaft doesn't have a number stamped on the end, so it's possible the re-builder may have used in inferior knock-off cam?

The cam shaft does have 616051 stamped on the shaft.

[Sugar Bear]

IMHO you've added a lot of longevity to the engine by preventing timing chain failure, I've seen several break. Even though yours may not have been stretched it still could have broken.

What is next a zero offset key?

[Sugar Bear]

Cam looks to me like a Benz cam with the logo ground off, that was common with companies that bought from the OE manufacturer but sold them under their own private label.

[stepper]

It was recommended that I remove the pulleys from the crankshaft to visually inspect the two alignment pins on the counter-balancer. I understand I don't need to remove the balancer in order to inspect the alignment pins. I've loosened the three bolts, and only the front two pulleys are loose.

Is the pulley closest to the balancer secured to the balancer via the large balancer bolt, or do I need to pound on the pulley to loosen it?

If it is just a manner of rapping on the pulley to loosen it, what strength of lock-tite should I use when re-installing the three bolts?