Timing Chain - stretched or normal?

[mikedsilva]

Motor has travelled approx 300o miles since rebuild.. new PIWIS timing chains and sprockets on IMS shaft.

I notice that left side tensioner is extended a little more than the right side tensioner. Never really paid attention to it till now. So cannot say for certain if it was like that when I put it together.

So, is this relatively normal? or should I be thinking to swap out the chain? Advice I've been given so far, is that this is relatively normal. There is still a relatively large space above the idler arm, before it reaches the chain box.

Thanks for looking.

[faapgar]

When the chain sprockets have wear the tensioner shaft will extend a little more to compensate.Looks normal.In the future just use the racing chain as they are prestreched.Fred

[VFR750]

Did you replace all sprockets? If not then the extended tensioner makes sense.

[mikedsilva]

Originally Posted by faapgar

When the chain sprockets have wear the tensioner shaft will extend a little more to compensate.Looks normal.In the future just use the racing chain as they are prestreched.Fred

Really?
I just learned something new.

[mikedsilva]

Originally Posted by VFR750

Did you replace all sprockets? If not then the extended tensioner makes sense.

sprockets on IM shaft are brand new. But not the ones on cams and idlers.

[Trackrash]

Here is my new chain just installed. IMO, you are good to go. On my last motor, I left out the base gaskets and had the heads machined. They looked similar to your chains and I ran it that way for 80K miles with no problems.

[BURN-BROS]

I am hearing reports of a problem with the sprockets bought thru Porsche. Premature wear and Lots of metal on the drain plug magnet

[356911930]

Are there better quality aftermarket chain sprockets on the market?

Thanks,

Rahl

[BURN-BROS]

The one's in question are made by Sebro. they are apparently the Supplier to Porsche now. They also sell a aftermarket sprocket.

Right now, I have heard the Rauch and Spiegel seem to be OK, however all of this is second hand information.

I have seen pictures of the wear and it's not pretty. The wear happens at the valley of the tooth where the chain rides.

[mikedsilva]

Originally Posted by Trackrash

Here is my new chain just installed. IMO, you are good to go. On my last motor, I left out the base gaskets and had the heads machined. They looked similar to your chains and I ran it that way for 80K miles with no problems.

hi Gordon
looking at your pic, the plunger from your tensioner is extremely compressed. What does your left side look like, compared to the right side?

[Trakrat]

sorry to jump in... but is it good advice to buy a new chain on a 100k+ mile motor?
I wasn't sure if I can reuse my original chain or if I need to buy a new one.

[Trackrash]

Originally Posted by Trakrat

sorry to jump in... but is it good advice to buy a new chain on a 100k+ mile motor?
I wasn't sure if I can reuse my original chain or if I need to buy a new one.

If you split the case it is normal to replace the chain.

Originally Posted by mikedsilva

hi Gordon
looking at your pic, the plunger from your tensioner is extremely compressed. What does your left side look like, compared to the right side?

Sorry, I can't find a pic to the other side with the tensioner installed.

The thing I find interesting is your chain on the right seems to be about the same distance from the plastic guide as on my motor.

[dannobee]

The other possibility is that the cams are now closer to the crankshaft after the overhaul. Were the heads flycut/cleaned up where they meet the cylinders? Were the cylinder base shims omitted or were thinner ones swapped out? Were the cam towers machined flat? Any of these things would cause a similar scenario as "chain stretch."

[mikedsilva]

Originally Posted by Trackrash

If you split the case it is normal to replace the chain.


Sorry, I can't find a pic to the other side with the tensioner installed.

The thing I find interesting is your chain on the right seems to be about the same distance from the plastic guide as on my motor.

Actually, to me it looks like you have a larger gap between chain and the guide. Which makes sense.

I'm not really too worried about it all. Going to button it up when my rockers arrive back from Craig.. he posted 2 weeks ago, and I still don't think they have left American soil yet!

[mikedsilva]

Originally Posted by Trackrash

Here is my new chain just installed. IMO, you are good to go. On my last motor, I left out the base gaskets and had the heads machined. They looked similar to your chains and I ran it that way for 80K miles with no problems.

I gotta ask.. what's that washer setup under your cam bolt?

[911pcars]

Chains don't stretch. They become "longer" when the chain pivot pins/holes wear and/or the chain sits lower on worn sprockets, sometimes a result of lube oil or lube dilution.

An engine I built long ago had enough crankcase spigot, cylinder and cylinder head machining that it required, in addition to shaving the chain box mount surface, a larger idler arm sprocket to take up the slack and restore the proper geometry for the chain tensioner/idler arm.

Sherwood

[Trackrash]

Originally Posted by mikedsilva

I gotta ask.. what's that washer setup under your cam bolt?

That temporary setup allowed me to set my timing without removing the wonderful new washer, when removing the pin, that Porsche uses on the new style cams.