3.0 SC knocking sound

[GDR]

I have a knocking sound from my 911 3.0 sc engine (https://m.youtube.com/watch?v=iYWawYPiCXM). I have tried listening with a stethoscope, and it was definitely loudest at the the left chain cover. Removed the cover and found this.



Way to stretched chain, right? I will have to change this, but could this be making the knocking sound? Or do you have any ideas about what would cause the sound?
I have uploaded a clip, if it helps.

https://m.youtube.com/watch?v=iYWawYPiCXM

Thanks!

[Sway Bar]

You need to address and change a lot ASAP. Your chain tensioner / idle arm is against the case so you are getting no tension...you could lose the chain at any time. Your idle sprocket looks heavily worn as well. Real Engine pro's will chime in but I would also address and look at the right side as well plus your cam sprockets etc.

You must have some big mileage on this engine or these components have never been changed?

[prschmn]

Sway bar is right. And give it more oil changes.

[GDR]

Thanks! I am not driving the car before this is fixet. I do not know the milage on this engine, but it is definitely not as good as expected.
Just bought the car and the knocking sound suddently started. Could the worn chain be causing the sound or do i have more problems?

https://m.youtube.com/watch?v=iYWawYPiCXM

[Alan L]

The idler arm is probably knocking on the case. Time to shelve the car and get engine out before more serious damage. At the moment it is just a restoration/maintenance job :-)
Alan

[Alan L]

Put a long screw driver on the top of the chain case and put your ear to the handle. That should tell you if you found the noise. You can fit chains with a join link - ie don't have to split the case. But it takes a fair amount of wear to stretch them like that. You may well find extensive wear in lots of other places when you pull it down. You can probably fit the joiner chains with engine in (just guessing), and time the cams etc without having to pull engine.
But if you plan on keeping it and getting some mileage out of it, you are probably going to pull the engine and do a top end tear down at least. The rest will depend on what you find.
While you are in there, be prepared for a fairly long list of replacement/wear/tear.
It depends on what you plan or want to do with the engine. But if it is looking like a complete rebuild and you don't feel up to it, a better option may be to swap in another SC engine. you would get some funds from yours towards it.
Depending whether the rest of the engine has as much wear as the chains.
Alan

[SoyRacer]

Engine needs a split-case rebuild. Basically - a full rebuild . . . . Now.

Chain is stretched beyond mechanical limits.

[john walker's workshop]

When the chain is worn that much, the tensioner is fully extended and still can't take up all the slack.

[GDR]

Thanks. Appreciate the answers.
I will put it back together, have a listen again with the stethoscope to hear if it is the idler arm that is knocking on the case making the sound, now that I have a better idea of where to listen. If so, I will replace the chain and idler sprocket for now, and consider a rebuild or 3.6 swap this winter.

Do you think this is making the noise, or could it possible be bottom end?

[theiceman]

Originally Posted by GDR

Thanks. Appreciate the answers.
I will put it back together, have a listen again with the stethoscope to hear if it is the idler arm that is knocking on the case making the sound, now that I have a better idea of where to listen. If so, I will replace the chain and idler sprocket for now, and consider a rebuild or 3.6 swap this winter.

Do you think this is making the noise, or could it possible be bottom end?

don't bother , the idler arm is hitting top of the chain housing . you need work regardless. your chain tensioner will thank you. I imagine your cam timing is out a fair bit too with a chain this worn. I would be curious as to what it reads before you do any work at all.

This was mine BEFORE I did my rebuild and I had a stretched chain .. look at the clearance at the top.

[GDR]

Originally Posted by theiceman

don't bother , the idler arm is hitting top of the chain housing . you need work regardless. your chain tensioner will thank you. I imagine your cam timing is out a fair bit too with a chain this worn. I would be curious as to what it reads before you do any work at all.

This was mine BEFORE I did my rebuild and I had a stretched chain .. look at the clearance at the top.

What shouldn't I bother doing? Sorry.
I see.. Mine is really stretched.
I am changing the chain no matter what. I would just like to know if the noise is caused by this before, so I can decide whether to remove the engine and do more work, or just the chain for now.

[Alan L]

Your other chain will be just as worn.
And as I posted before - unless the engine has had other work done, and the chains ignored, there will be lots of wear elsewhere. But the stethescope/screwdriver will tell you if that is the noise, or elsewhere.
You may even be able to feel the chain issue on top of the case with engine running.
Alan

[0396]

Well, you came here for some advice. And you've received some well educated/live advice. Based on what's been presented, the advice to rebuild is pretty spot on. Unless the funds are not convenient at this time.
Its like the oil change advice...who ever previously owned it, did not maintain it well.
Just my uneducated view. Good luck.

[Norm K]

Originally Posted by Alan L

Put a long screw driver on the top of the chain case and put your ear to the handle.

This is certainly a tried and (often) true way of identifying the source of an engine noise, except that in this case it means starting this potential grenade even one more time. The engine clearly needs a rebuild, or at a minimum new chains, idler arms, gears, tensioners etc., so why take even the slightest chance at this point?

[VFR750]

That is a nasty sounding engine. You may be hearing the tensioner hitting the case. You may also be hearing the valves crashing the pistons.

Sorry to say, there is no good reason to start it again.

Judging from the internal color, this poor engine has not been maintained very well. Oil wetted surfaces should not look rusted.

[Cairo94507]

I listened to that video and had to shut it off. That engine needs to come out and be pulled apart and rebuilt correctly. I would not drive it for fear of doing real damage. That poor car was not treated well at some point for sure. Good luck.

[theiceman]

Originally Posted by GDR

What shouldn't I bother doing? Sorry.
I see.. Mine is really stretched.
I am changing the chain no matter what. I would just like to know if the noise is caused by this before, so I can decide whether to remove the engine and do more work, or just the chain for now.

sorry I wasn't clear . I meant don't bother running it more as you are likely to do more/continue damage. If you want you could put chains on, time cams, button it up then listen. if its something else at least your chains are done.