How Easy Is It to Stretch Timing Chain?

[peter540]

When I first re-timed my '03 540 after doing TC guides, etc., I got the P0021 code. My Indie suggested I crank the TC tensioning tool far tighter than spec the next time I tried timing. I did that -- tightening the tool with my torque wrench WAY beyond .7 nm (OEM/TIS spec). Could that have stretched the chain?

I ask because my car, after multiple re-timing attempts (where chain was tensioned correctly), is STILL out of time. In listening to the engine, I hear various noises, including:


What I think is Vanos "dieseling"/rattling. I've done the Beisan seals; I theorize they're making noise because the engine's out of time.
I'm also hearing a subtle electrical "ticking" noise near the vanos units, and I assume that's the solenoids.
Unsure whether I'm hearing some chain slap, since I don't know what that sounds like. The guides and tensioner are new, but the chain, as I mention, was tensioned extra-tight in one of my timing attempts, and it's the original 83k-mile chain. Could it have been stretched beyond the range of the new tensioner?

I of course ask all this because I'm hopeful the answers I get back will be that I couldn't have stretched the chain much when over-tightening. I dread the thought that I DID stretch the chain and, as a result, that I have to pull off the whole front of the motor again.


Thoughts?


--Peter

[sktn77a]

Chains don't "stretch" in the classical sense, but the pins and roller can wear if they are dirty, thereby increasing it's length very slightly. I don't think that's your problem, though.

[peter540]

Thanks, sktn77a. Glad to have that answer.

Any others with input? You know what I'm hoping for -- more comments like sktn77a's.


--P

[514mach1]

Yep, probably didn't stretch it at all by going tighter. But a chain that's tensioned way too tight will wear (and that means it gets longer) much faster than a loose-ish or not too tight chain. I hope the noises aren't anything related to valves touching pistons.

[topaz540i]

The motor would be putting way more force on the chain than that tool ever could. If it was that tight i would think the center u shaped guide would have cracked first.

[peter540]

And I don't think I put enough force on the chain to crack the center guide. From what I could see of it when I had the oil pan off recently, no cracks, and certainly no plastic has broken away.

I think this is all related to the timing.

514Mach1, if my valves were hitting the cylinders, I'd think that the engine would be running poorly. It's just missing a little at idle. Still, I do worry about what's going on.

Throwing in the timing towel and taking the car to a trusted indie to retime; I hope to be allowed to observe his procedure (and maybe help with it). First, he wants to get the engine to TDC and measure the pistons' position, his theory being that perhaps the flywheel is bent -- that would throw off TDC as measured by the flywheel. Topaz, I know you've heard my mention of this theory.

I'll have to deal with all of this after dealing with my AC system first, though. Compressor blew up (internally), leaving the refrigerant blackened (metal shavings, burnt oil). So I'll be replacing the compressor, the receiver/drier, condensor and expansion valve. Also will be flushing the system ultra-thoroughly and will have a shop put a vacuum on the system for several hours to make sure the hoses and evaporator are as clean as possible before recharging the system. Actually have the compressor mounted (but no lines yet connected) already. Not looking forward to the contortionist moves I'll have to make to get the expansion valve out.

[rf900rkw]

Stretching the chain, not a chance. The guides will give way first.

[514mach1]

A slight bend in the flexplate won't throw off the TDC indexing any measurable amount, and certainly not enough that you could tell without pulling the cylinder head and using machinist tools to measure degrees of rotation vs the piston dwell.

[rf900rkw]

You don't have to pull the head. I drop a dial indicator through the plug hole and index the marks that way. And with a deft touch and a bit of experience, you can do it with a screwdriver and be within a degree.

Peter, the offer still stands. Bring the wife and kid up for Busch Gardens, Williamsburg, or beach, and we'll get to the bottom of that critter's ailments.

[peter540]

A very tempting offer, Randy, and THANK YOU!. Challenge is that we move from B'ham to Atlanta next month. Wife starts a new job in August, daughter starts new day care/school. But maybe I could swing a solo road trip.

You're right, BTW -- no plan to pull the head. Going in through the spark plug hole.

I think we'll find that nothing's out of whack, which simply means I am a dumbass who can't figure out how to time this darned motor. But really -- I do good work. No issues with Zionsville, front-end suspension rebuild, Dice and BSW audio system stuff, AC system "rebuild," etc. Plus I've done my wife's Jeep Wrangler's cooling system, valve cover gasket, shocks.