I’ve been working on getting the car mildly roadworthy. Engine is still running roughly and has an annoyingly loud clicking noise that I’ve tried to ignore while I tended to other things.
I thought it might be a valve knock, but I listened to the entire valve train with a stethoscope and the noise is all right at the front of the valve cover. So I adjusted the timing chain tensioner several times, without much difference, until the whine told me it was too tight.
Did a little more digging and found a reference to some sort of “friction pad” for lack of a better term in the top of the valve cover to protect it when the timing chain comes into contact with the valve cover, and if this gets worn or too old it can fail.
Now I’ve never heard of this before, nor do I remember seeing anything in the valve cover that would indicate this exists.
Has anyone heard of or experienced this situation before? If it does exist, is it renewable or is the only remedy replacement of the valve cover?
Any info would be helpful as I am about to remove the cover.
OK I think that was BS about some appendage in the van cover. In any case I don’t see any scoring in the metal from the chain hitting the cover, so we can rule that out.
The chain tensioner was still a little tight, but I adjusted that more exactly with the cover off. I do see a little mark where one of the sprocket bolts may be contacting the cam cover. I’ll include a picture.
Cam sprocket bolts are usually half-depth. Possibly you’ve got slightly deeper ones fitted and they’re catching? They’re the same as a crankshaft pulley bolt except for the head being shallower.
I definitely have full size heads and they are extremely close to the edge of the cover. I am pretty sure I got the bolts from DBE when I bought the sprockets, cams, bearings, etc., but maybe not. Certainly seems like a suspect.
Check the free movment - fore and aft - of the timing tensioner. Sometimes they get twisted and they can sit hard against the timing chest, transmitting noise.
Crank pulley and cam sprocket bolt comparison. It looks like Lotus just machined the top off the head of a crank bolt as they are no identifying marks on the heads of those.
Just a longshot and FWIW - I was worried by a tapping I had on an engine I rebuilt recently. (Not a twinc ) I could have sworn it was something mechanical - Was it a small end? - something from the valve train ? I was getting ready to remove the engine to see what I had cocked up and at the last minute tried a length of hose between my ear and the area round the exhaust manifolds - Voila ! - Just a misfitted exhaust manifold gasket. The shape of the gasket was very similar to a twin cam gasket and it had been put on upside down . Imagine my relief !
Thanks for the suggestion and I’ll definitely keep it in mind as I move forward. I’ve got the cam cover off already, and at least some telltale scrape marks on the cover out by the sprocket bolts. I’m going to change out the bolts for ones with shorter heads and work my way from there.
I had a ticking suddenly develop in a Ford block (not Lotus). It turned out to be the spark plug. The center insulator had come loose from the threaded metal part and was moving in and out a bit with every compression. I was astonished but the mechanic had seen it before.
Should there be a lock washer on the camshaft sprocket bolt? There is the large washer that fits into the sprocket, then the parts diagram shows a smaller washer between the bolt head and the large washer. It doesn’t specifically state a lock washer on either the RD Enterprises parts diagram or the DBE parts diagram.
I assumed it was a lock washer, which for the size bolt used is quite thick. An SAE washer would be less than half the thickness, which would probably account for the discrepancy. I checked and RD does not supply a smaller head on the sprocket bolt any more, so theoretically the bolts I have should fit. Of course, this is an Elan, and mine was definitely started on a Friday and finished on a Monday…
Yes a spring-washer / lock-washer is present there. I’ve seen them have thin profile ones but usually they are - what looks to my eye at least - standard thickness.
Wanted to give an update on this. It’s been a while as I went off chasing a weak spark condition after I changed the bolts on the cam sprockets.
So good news/bad news. The spark issue was resolved after several marathon troubleshooting sessions. But the clicking noise remains.
To go over what I’ve done so far:
Pulled the cam cover and replaced the sprocket bolts with shorter head bolts.
Adjusted the timing chain
Ensured that the timing chain tensioner had free movement fore and aft.
Checked all the exhaust bolts to make sure all were properly snug.
Started it up this morning. Happy to say the spark issue is resolved, but the clicking noise remains. It’s more intermittent than it was before, so I’m still hoping it’s chain slap; but if anyone has any other ideas or things to check, please let me know
Check the alternator/dynamo bolts and adjuster bolts. i had a front end noise that I thought was chain/valve gear related, but it was just a slightly loose alternator bolt.
