Timing Chain noise L18

[Povi]

Long time reader, first time poster because I have arrived at a mental block for my level of experience

I've read every thread on here about timing chain noises and cannot arrive at a conclusion given what I'm seeing and where the engine is at:

 

'74 620 with L18, assuming 156k on the clock (ticked over), running perfectly fine and quiet for the year-ish I've owned it. It's tired but has been very reliable.

Had it at a friend's workshop for two weeks where I did a bunch of work to it (didnt touch the engine, all suspension/cooling/cosmetic)

Go to start it up and TC makes rattling sound at certain rpms, as engine warms up it eventually rattles lower down the rpm range until constant on idle when engine warm.

Sound is front/top end of engine, screwdriver to ear sounds very much like TC, it's very much a sound and frequency like chain links contacting with a hard surface 

Will go away at higher rpm but for city driving it's audible from inside cabin 80% of the time. Drives fine power-wise.

Pulled valve cover, no obvious issues to see, nothing visually out of order on the valvetrain either. 

Rotated clockwise to TDC and timing chain is very tight on tensioner side, has roughly 1/2" deflection on pulling side.

The two TC marks are almost perfectly aligned on crank sprocket (which is in position 2)

Pulled dizzy and shaft is at 11:25 position

Timed to 12 deg at idle with a Pertronix ign

Use SAE30 oil, filled halfway between high and low marks on dipstick.

 

At a loss for where to go from here, it seems like everything is 'in order'.

Next thoughts would be get an oil pressure gauge and tachometer just for more data points but not sure what that could help to indicate in this instance

 

Have I missed something obvious? Not a professional mechanic, and try my hardest to not be an idiot if I can help it.

 

 

[datzenmike]

I would check the valve clearances on the engine when hot. Should be 0.010" intake and 0.012" exhaust. This eliminates valve noise as the cause. 

 

The bright links are 42 links apart and align with the dots on each of the two sprockets when installed but as soon as the engine starts this is lost and as the chain is well over 100 links in length this alignment may happen only every several dozen or several hundred turns, I don't know. It's almost random.

 

The guides are plastic coated. If worn through it's metal to metal.

[banzai510(hainz)]

next time you have the valve cover off look down  front cover and see how much the tensioner is pushing out. youll see the shiny part way out or jammed at a angle.  I had one hat was way out and angled and was grround down waering out at a 45deg angle.  chain was still tight.

 

next I would do like MIke said and tighten up the rocker arms.  I myself do tighter(.006 in .008ex cold)  if you loose a cylinder then its tootight and NO compression.

 

I would look under there and see if the alternator arm or bolts loose on bottom causing a rattle. Radiator bracket ect.......

 

 

if the tight side guide is tight and rotate clockwise keeping soem tension on it the slack side should not really have a whole lot either

 

 

so get the flashlite and look down

l20fronttimmingcahininstall.bmp

Edited November 1, 2022 by banzai510(hainz)

[banzai510(hainz)]

[datzenmike]

Take note above..... NO FRAM FILTER.

[Stoffregen Motorsports]

The soft material on the guides and tensioner get hard with age, and they can deteriorate, causing metal to metal contact.

 

If the head has been milled, there could be too much play in the chain, causing the chain to contact the oiler.

 

Some grinding may be required in the mounting holes of the guides to get them properly lined up with the chain. It's pretty common and largely overlooked.

[datzenmike]

 

The L16/18 is set on the #1 hole on the cam sprocket at the factory leaving two more adjustment holes for correcting cam timing in the event of chain stretch but I've never seen this. I bet the double row chains never wear out. Usually milling the head is the cause of added slack that moves the Vee notch to the left in the picture above. The etch mark in the cam thrust plate is 4⁰ wide.

 

 

[Povi]

Thanks so much for all the information here. I had a moment this afternoon to do some sleuthing. 

 

We're at TDC rotated clockwise. You can even see faintly the notch at 0 in the background here. Here's dizzy shaft

 

 

Here's the timing notches, also note the strange damage there which I can only assume was a poor installation before my time. It conceals the number 2. No obvious fragments or anything else anywhere to be found, I assume this has been this way for a while but the noise has only started in the last few weeks of driving.

 

 

Down the barrel everything looks fine, straight (to me, the one that doesn't know whats wrong LOL)

 

 

Noticed this shinier area here which could be chain links? seems a strange place for that - if the slack side is that loose one could assume the chain is flying across and is rubbing against itself all the way across the gap? but slack side is taught at TDC here, and pulling side has about 1/2" deflection

 

 

Now looking for more signs of wear - this found on pull side. The tops of the chain links are hard to discern if there's any visible damage but if I wanted to err on the side of caution it feels like they're showing signs of rubbing

 

 

And the underside of the valve cover

 

 

Hopefully this video works - this is not even full heat in engine but the sound is clearly audible at idle and with a rev. It seems to get worse the more temp goes into the motor.

 

 

[datzenmike]

The gouge on the cam sprocket was caused by the fuel pump arm.

 

I don't see anything wrong.

 

The noise in the video sounds like normal lifter noise. The clearances open wider as the engine heats up so yes it will seem to get louder. If setting to 0.010" and 0.012" the engine must be up to full operating temperature or they will open wider and make more noise when it does get warm.

 

Like Hainz says you could go slightly tighter, like 0.008" intakes and 0.010" exhaust HOT. If it quiets down then that was the cause.

[Povi]

I'm glad to know that nothing's ostensibly wrong there, however I'm confused as to why the noise came out of nowhere in the first place? I drove it to a friend's shop to work on it for two weeks, then first start up it's rattling away but had never before that. Didn't touch the engine at all in that time other than install Pertronix.

 

Next chance I get I'll check and tighten valves!

[datzenmike]

Well eliminate the valve clearance as a cause.

 

If you warm the engine for 20 minutes and quickly set to TDC like the above picture you can quickly check/set both valves on cylinder #1, the intake on #2 and the exhaust on #3. Quickly turn the engine ONE turn to the TDC on the exhaust stroke. Set the exhaust on #2 the Intake on #3 and both valves on #4.... and done. This eliminates repeated bumping of the starter and is easily finished before the engine cools down too much.

 

 

 

This pattern is caused by oil cast off from the timing chain.

[Stoffregen Motorsports]

Could it be another source of the noise? Maybe loose crank damper/pulley, or other accessory like alternator? A loose or broken alternator top bracket or the one that holds the air cleaner steady can sound like that. Could it be a tiny exhaust leak? Or a broken exhaust hanger?

[Povi]

Finally found some time to address this. Have double checked all kinds of loose bolt/part type areas and everything seems snug there. Noise definitely sounds like inside valve cover

Got it up to temp after a half hour drive, checked the valve clearances straight away. None were too far off, but they are all now .008 IN and .010 EX hot.

Still very rattly? Most noisy at idle and lower rpms. Have attached a video.

I know you all say these L motors are noisy as is, is this just a case of me hyperfixating on that and should I just relax and turn the radio up when I drive?

 

 

[datzenmike]

Hot setting is 0.010" In. and 0.012" Ex. 

 

Your setting will work but... the valve is cooled by direct contact with the seat. The tighter the valve clearance the less time on the seat.

 

It'll be quieter.

[Povi]

2 hours ago, datzenmike said:

Hot setting is 0.010" In. and 0.012" Ex. 

 

Your setting will work but... the valve is cooled by direct contact with the seat. The tighter the valve clearance the less time on the seat.

 

It'll be quieter.

 

Ahh, gotcha. I was under the impression the noise was from too large a clearance causing a 'tick' when the valve and rocker arm make contact, so a tighter clearance would make that less of an impact. So Hainz's tighter clearance made sense to me. Glad to be told otherwise (I'm still learning)

I will loosen up those .002" after my next drive

[datzenmike]

Oh you can run tighter clearance and it will be quieter but I would keep a close eye on these clearances that they don't start closing up. For example as the valve seat wears, the the valve rises as it sinks up into the head and the clearances narrow. Just check more often and keep ahead of any changes.

[Stoffregen Motorsports]

It does sound noisy. Are you sure you had the valves all closed when you adjusted them? The "book" says to adjust the valves at TDC and then at 180 out, but I like to have all rockers pointing up in a V on each cylinder when adjusting valves.

 

Did you look for wear on the rockers? Are all mousetrap springs on the rockers? Have you double checked the exhaust for leaks? An exhaust leak can sound like a valve tick.

[Povi]

Drove it around today, checked valves again while nice and hot. Decided to keep them at .008 and .010 for now to be certain that's not the source of the noise. Can change later. Small damage on cam seen in image, but that can't possibly be the source of this racket. It's a more frequent tapping. All springs, rockers, everything else looks totally fine.

 

 

Still the same noise, at idle and lower rpm. When revved higher it seems to disappear (and not just become so frequent it sounds like it's gone). Twisting distributor to change timing doesn't affect it

Spent a solid few minutes at full temp listening to it idle, rev, trying to pinpoint where exactly it is. Part of me wants to say it's almost in the block, if I stick my head down the hot side of the engine it almost sounds like its coming from piston 1 or 2. Putting hand on block doesn't generate any discernible knock feeling.

Since it's right in that same area where I can stick my head to listen, I think checking for exhaust manifold leak might be next? I've dealt with one of those on an old toyota before and it didn't sound like this. The muffler under the car looks like a shotgun victim with the amount of rust holes in it, but the manifold area everything looks fine.

Is there a way to check for them without having to rip everything off? Like is soapy water on a cold/mid temp engine a suitable test?

 

EDIT: also, there's a considerable amount of air pressure when I take the oil fill cap off the valve cover when running. Could a damaged valve be another possibility?

[datzenmike]

What oil are you using?

 

Excessive blow by is past the rings. The valves have nothing to do with that. If blowing at idle that isn't good. Do you think you could pour oil in? or would it blow it all over? Perhaps a compression test to look for a bad cylinder.

 

 

[Povi]

SAE30. It blows at idle. I don't think it'd be strong enough to blow oil everywhere but it's certainly notable pressure.

I've known this for a little bit and of course addressing it is on the cards but I'm more just trying to figure out if it is a contributing factor to this ticking.

Trying to at least drive the thing a little bit more before I need to pull the engine out and do rings and whatever else that snowballs into haha

 

I'll do a compression test, but I'd still like to check for exhaust leaks too.

 

It drives very solidly and accelerates healthily. There's no indication that it's down a cylinder in that way

[Crashtd420]

Where is the top vent and the pcv valve connected?

Not sure how much pressure your talking about but I would make sure those are not blocked..   

 

[datzenmike]

8 hours ago, Povi said:

SAE30. It blows at idle. I don't think it'd be strong enough to blow oil everywhere but it's certainly notable pressure.

I've known this for a little bit and of course addressing it is on the cards but I'm more just trying to figure out if it is a contributing factor to this ticking.

Trying to at least drive the thing a little bit more before I need to pull the engine out and do rings and whatever else that snowballs into haha

 

I'll do a compression test, but I'd still like to check for exhaust leaks too.

 

It drives very solidly and accelerates healthily. There's no indication that it's down a cylinder in that way

 

Oil.... I meant is is regular off the shelf or does it have a high ZDDP level. I err on the side of caution and use an oil that has the same anti-scuff additive package as when the engine was new. Starting in the '90s oil makers have been reducing the ZDDP levels in their oils. It's about half what it was and probably will go lower. Your cam looks fine and I'd like to keep it that way.

 

Some blow by is normal and usually increases with load. Severe blow by, specially at idle is very bad rings and even a damaged piston. Sounds like it may be normal.

 

Driving it is an excellent idea. Helps to 'loosen' things up. Unless you have a blue cloud following you a rebuild is a long way off.

[Stoffregen Motorsports]

How about a piece of something bouncing around in one of the combustion chambers? It has happened before. The tip of a spark plug that has broken off, or a tiny screw or washer that got lost down the carburetor could make a sound like that. One way to tell is to remove the spark plugs and have a look at the tops of the pistons. If there is any foreign object in there, you'll see marks on the piston dome.

 

Air coming out of the valve cover? That's not normal. Have a look at the baffle that's riveted to the underside of the valve cover. Is it blocked up with gunk?

[Povi]

On 12/16/2022 at 5:59 AM, datzenmike said:

 

Oil.... I meant is is regular off the shelf or does it have a high ZDDP level. I err on the side of caution and use an oil that has the same anti-scuff additive package as when the engine was new. Starting in the '90s oil makers have been reducing the ZDDP levels in their oils. It's about half what it was and probably will go lower. Your cam looks fine and I'd like to keep it that way.

 

Some blow by is normal and usually increases with load. Severe blow by, specially at idle is very bad rings and even a damaged piston. Sounds like it may be normal.

 

Driving it is an excellent idea. Helps to 'loosen' things up. Unless you have a blue cloud following you a rebuild is a long way off.

 

It's off-the-shelf SAE30. Can you recommend a brand with higher ZDPP or is it more like getting it as an additive?

 

With this problem still going on despite ruling out obvious TC issues, valve lash, loose accessories... my attention now is to consider - since the timing chain is tensioned by oil pressure, is it possible bad rings/pistons are pressurizing the tensioner too much and it's causing the noise through that? 

I drive it around the neighborhood to do errands and sorta 'force' the problem to worsen, and so far it seems like it's become noisier, most distinctly still a constant chain-dragging type noise which leads me to believe this is still a timing chain issue.

 

I plan to do a compression test next time I'm working on the car, and also considering plumbing in an oil pressure gauge to get more accurate readings there. Good next steps?

[datzenmike]

I measured the diameter of the plunger on the tensioner years ago and worked out the area of it and applied 55 PSI and the pressure amounted to about 6 -7 pounds on the chain. Now this is at max oil pressure which should be above say 2500 RPMs. Below that and specially at idle is way less perhaps 2-3 pounds, a large can of coffere... basically nothing. If you have ever installed one, the spring pressure is very high and difficult to push in by hand. The oil is there to lubricate the plunger more than anything.