clacking noise at tickover

[miked]

Just got my S4FHC on the road after building over about 7 years. Done a 100 miles of so of shakedown.

I put the engine together a few years back, all the right bits. Pleased with car and all is great, pulls well, good oil pressure and cooling system is working well with nose positioned rad. Tickover balanced etc with new 151's.

At tickover, when warm, I am getting a noise from around the chain tensioner quadrant area. A light clacking noise. When revved it goes or is screened.

I searched and found this old thread which I can relate to. I had the big screwdriver in my ear around and water pump and all is quiet as are the cams. It seems to come from the tensioner. So paranoid am I that I have pulled the cam cover and will check everything. Valve clearances, torque head bolts (whilst in) and lift and examine the quadrant and sprocket. Also pull the spring and plunger. I have verniers so was paranoid about them. Never again, dowels are good enough. Can't be doing with more hardware to fail.

elan-archive-f16/clacking-t5253.html

Any thoughts on my description and old posting are most welcome. I like the one about plunger loose on the bore. Seems feasible.
PS got no servo or non return valve. Alt' bracket is cast solid jobby and tight.
Mike

[AHM]

I am in similar position to you. The S4 is on the road again after a 7 year break... or was it 9 years?.

I say similar because my chain is a fraction too tight with a hot engine and yours sounds to me to be a fraction too loose.

There shouldn't be anything clacking or flapping - It isn't a slack remover it is a tensioner.

[miked]

AHM

Althought new kit, mine is a tad tighter than usual in odd places through the turning cycle. I will be slacking off slightly after doing my other checks.

"There shouldn't be anything clacking or flapping - It isn't a slack remover it is a tensioner."

Not sure what you are telling me above!

Mike

[john.p.clegg]

What I think he's saying is that you should use it to take up the slack then wind it in a bit more to put some tension on it (spring loaded) ...

John

[miked]

Thanks John,

I always do and watch it tension up from slack and do the correct pull/push setting. I have not had problem with chain setting or slack. Nothing is flapping about in that respect.

Mike

[AHM]

Yes, it needs to always be under enough load or it will flap around.

The setting in the manual is a best estimate when cold, suits all, approximation when hot, might be right if you are lucky setting. The tension has to allow for the change in effective length due to the expansion of the engine and the changing loads in the chain

What you have described appears to me to be a resonant flap in the slack area of the chain where the tensioner is. It also sounds to be a low frequency flap, which is why I am suggesting it is too loose. You can tell if it is too tight as it will begin to whine.

I set the tension up when hot by tightening until it begins to whine, then backing off until it is quietest.

Not sure what you mean by tighter in some spots than others? Do you mean that as you rotate it the valve springs put tension on the chain, or do you mean that you have a bad chain/sprocket?

[miked]

Yes, agree a low frequency flap, a resonant one. That hangs together. It is not there when cold and appears to go when the RPM rises.

As regards tighter in some spots than others; I have new sprockets and chain but it does seem tighter in parts of the cycle than other. So as you say it may be when against the valve spring action in those postions.
I do intend to run it and play with the adjuster as you describe but will check the other bits while in there. Always been a bit afraid of playing with the tesioner when the engine is running.

Thanks Mike

[gav]

Interesting
I have a similar very loud clatter when the engine is idling after a run.
I have had the chain hitting the top of the cam box before now because the tensioner thread had stripped and it was slackenning off in use.
I fixed the tension and treadlocked the adjuster in position just to check and when I ran the engine it was fine when cold but made a dreadful noise when hot. This could have been down to me over tightening the cam cover and over compressing the gasket. I think the cam cover has been decked in the past and is now sensitive to set.

Anyway, I lifted the cam cover and checked all of the valve clearances - all perfect but for one exhaust valve which seems to have a little too much clearance (by about a thou and a half).

I checked the chain tension cold and it felt a little tight to me so I am relatively stumped now - I have replaced the cam cover gasket and will run again to see. I can't believe that such a small valve clearance issue would create such a noise and I am sure that the problem is at the head end rather than the block.

If the chain is too tight, what will happen when the engine warms up?

Thanks
Gavin

[AHM]

Miked, it isn't nice to adjust with the engine running especially if you have mechanical fan, and not least because with the locknut backed off the vibration can loosen it. Warm-up, Switch-off, adjust, start, go for a drive....etc

With a new engine it is iterative, so as you say there are plenty of other things to check, and you will be having another go once it is run-in.

Gavin,
Too much valve clearance would just cause a regular tap - one a half thou isn't that much and the clearances reduce as the engine wears.

Because of the position of the cam lobes on the valve springs they can load the chain making it appear tight or loose so you may need to apply reasonable force when measuring to get all the slack in the right place.

Too much chain tension will whine a bit like a worn bearing or an electric motor under heavy load, and changes with engine speed. Too much tension isn't good, it will cause things to wear quickly. As the engine warms-up the chain tension gets greater and if it is too tight the noise gets louder.

My suggestion would be to get a new adjuster and start with the factory settings - then make small adjustments if you need to from there - make notes so that you can get back to square one easily.

[rgh0]

If the clacking noise is regular and occurs at half engine speed -i.e at idle of 1000 rpm about 500 times a minute or 8 times a second and only occurs when the engine is hot then it is probably excess clearance of a cam follower in a bore. An exhaust gasket to the head can leak and can produce a clacking sound at half engine speed at idle but that would appear to be from the other side of the engine.

If its at a frequency that's not half engine speed then try to identify what is the frequency and whether it relates to components that move at the relevant frequency.

cheers
Rohan

[miked]

Not run since to see frequency as cam cover is off, but I think I have found it.

Took quadrant out and sprocket. See Photo's. In simple term the sprocket looks too thick and the chain is bedding and cutting it way into the thickness of the metal. See marks. I am not a metal guy but that is going to make noise while it cuts in. No doubt if I thrashed it around for a while it will go quiet. Not happy with that. Just comparing with the main sprocket you can see it is much thicker. Also it has a neck that tapers down rather than being a parallel.
All my old bits are not here to comapre with. At a mates.

This was a new sprocket. When I gather more info' I will post it back. Must be 5 years since I bought it. Anybody got an old one to look at the side profile and thickness.

For Ref, Nothing wrong with cam followers. All checked during rebuild by trusted engine man.
Head re torqued and valve clearances. Just 4 were a tad tight.

Re Chain Lube, going to run with cover off, made some Lexan cam covers. Pretty sure it is ok though as the chamber was well wet with oil.

Mike

[john.p.clegg]

Mike
Lexan sounds great but metal filings in the engine doesn't...

John

[elanman999]

Mike,
Can you measure the width of the sprocket and the width of the chain ? The chain should be somewhat wider than the sprocket. At a guess I would say by at least .005". Obviously you'll have to try and measure on an unworn part of the sprocket. Also can you compare your chain as it is with a new chain?
From your pics it does look as if the sprocket is too wide as they do not usually wear both sides evenly like that.
Cheers
John

[miked]

Thanks for replies John E and John C, I had to go and do Granddad duties.

Yep Lexan covers will allow me to run it and watch per very good posting about oil hole proving with cling film.
Re filings, what do you suggest? Flush down the front cover, and oil and filter change.

I measured the internal of the chain at 0.228. The unworn part of the sprocket is 0.207 to 0.208. The worn part is 0.202 to 0.203.

I think you are dead right about the thickness. I jumped the gun there seeing the wear. The above obviously gives clearance. Looking at it again and thinking about the wear pattern I think it is misalignment. The wear is cut in to one side of the tooth. If you twist a sprocket on a running chain it will cut in and wear on opposite parts on either side. It is like that! I don?t think the sprocket is running at 90 degree to the pivot pin. The pivot pin was also new and is not worn. The wear shown is just from 100 miles.

Just holding the quadrant in my hand by the pivot pin the sprocket looks at an angle. I will set it up tomorrow and do it properly. The quadrant looks like the culprit. What a bummer.

PS not got a new chain to measure at the moment.

Mike

[elanman999]

Mike,
I've just adjusted my tappets, so whilst I was in there I measured the chain and a sprocket. I get very similar dimensions to you.
Re filings. With any luck the filter should have done it's job and all will be OK. But to check the state of the oil system I would remove all of the cam bearing caps (one at a time if you don't want to take the cams out) and look at the state of the bearings. If all is OK, as it should be, I might change the oil and filter just for peace of mind. If the worst has happened then I would drop the sump and re-shell the engine.
I would be interested to know what your findings are as to the sprocket being out of square with the pivot.
Cheers
John