Noise from the engine area

[LCRJ]

Hi All,
I had driven at high revs at the track for a long time. When I started the engine the following weekend, I started to hear a crackling sound. Considering the construction of the engine, to the untrained eye it seems like a hammering sound when the tappets close. My impression is that the sound is like a coin striking steel. This sound had been heard before when the engine was cold, but the sound disappeared when the engine warmed up, perhaps because the oil had been spread after start-up. This time, however, the sound took longer to disappear after the engine had warmed up or the sound started again. It does not bother me when I start running, but it sounds like it is ringing, or it starts ringing when idling at traffic lights. My friend applied a stethoscope and couldn't find any particular place where the sound was occurring, but he measured the valve clearances and found that IN#3 was over and the chain tension was slightly loose, so he adjusted it. Unfortunately, this did not solve the problem. The engine is fine runnning. From your experience, what could be the cause? Any advice would be appreciated.
Thank you, Hiro

[Pastapesto]

Hiro
Hi how are you?..... Had a similar sort of problem a few weeks back..... There was a clattering/rattling sound coming from the engine..... All good powerwise apart from this horrible sound..... Turned out to be the bearing in the dynamo had collapsed and was moving forwards and backwards/ the pulley/fan arrangement hitting the front plate (all on the dyno)..... See if there is any for and aft movement from the dyno/alternator..... Worth ruling out before you get worried...... Good luck.... Hope you find the problem soon....

All the best

Adam

[LCRJ]

Hi Adam,
Thank you for your input. It's nice to heard from you again. I'm fine and getting old. I still doing some reserch works and enjoing Lotus TC tuning thing.
Yes, same situation like you Adam. There are a clattering/rattling sound coming from the engine..... All good powerwise apart from this sound.....
Apparently, the sound is only noticeable when idling during warm-up. When the revs are raised, the sound disappears (you can't hear it, or it doesn't bother you). I just drove it around the neighbourhood, returned and left it idling in the garage, and that sound is not bothering me. The sound is regular with the engine revs and from the sound impression I think it is around the valves. However, the valve clearances are normal so I am guessing it could be due to the condition of the cam followers or a gap. But I have no idea if that is the cause of this sound. I have confirmed that the dynamo and alternator are fine. I would like to hear your opinions on this.
Thank you. Hiro

[Pastapesto]

Hi Hiro...... I'm not really the person to ask about possible cam wear/bucket wear problems as I'm not that knowledgeable in the technical aspects of the engine internals..... But...... I was asking someone who is knowledgeable the other day (before I discovered the dynamo bearing problem) and he suggested trying to see if the chain adjuster might need adjusting slightly - and seeing if the noise disappeared...... Might be worth a try Hiro?...The odd slight tapping noise from the cam cover area has never worried me but it depends on how noisey and annoying it is..... Rohan might be a much better source of knowledge about your noise......
Please let us know how you get on..... All the best and good luck..... A

[Craven]

Hello Hiro,
Good to hear from you, my project is now complete although not many road miles yet,
Just one point camshafts are running at half engine speed.
BTW your English is very good much improved.

[rgh0]

If its coming from the valve area and follower clearances are OK then just really a couple of possibilities i can think of.

1. Excessive follower to sleeve clearances allowing the follower to rock in the sleeve. This tends to be most noticeable at low revs and when the engine is cold which appears to match your symptoms. However it usually comes on slowly over time rather than happens all of a sudden.

2. A broken valve spring. This could happen suddenly especially after a period of enthusiastic engine use.

cheers
Rohan

[LCRJ]

Hi Ron, It's nice to heared you and congrad finished your project. Please spending happy miles with your car. My english still not enough. So I will post the sound files shortly. Speak to you soon. Hiro

[LCRJ]

Hi Rohan, Thank you for your input. I was hoping for your advice!
Yes, valve clearance is OK and chain tension is too.
It is not clear where the noise is coming from. Based on the periodic occurrence and my impression of the sound, I am guessing that it is near the valve. But on the other hand, it is a clear sound, so if it is coming from under the cam cover or from the cam follower, it might be a bit muffled.
If, as you say, the clearance between the follower and sleeve is excessive and the follower is swinging in the sleeve, would it be relatively easy to identify the source?
I've had a similar sound before, but occasionally when the engine was cold, but it went away quickly. This time it is assumed that the clearance has increased by using the engine to high revs.
If this is the cause.
1, Is it safe to continue driving for a while?
2, How should I think about the timing of the overhaul?
　If the sound becomes even louder after continued driving?
3, If the cam followers are worn out, can this be solved by replacing the cam followers with new ones or do the sleeves need to be replaced?
4, Do you have information on the specified size of the cam followers and the specified size of the sleeves?
If the spring is damaged, this is unlikely, as the same sound will continue whether the engine is cold or warm, I think.
However, both the cam followers and valve springs have been in use for over 10 years (although the mileage is not so high), so is it generally time to replace them?
Any further advice would be appreciated.
I will try to upload a sound file shortly.
Thank you in advance for your help.
Kind regards,
Hiro

[rgh0]

Hi Hiro
One other possibility I thought about is an exhaust manifold gasket leak. A leak can create at tapping sound that sound like metal on metal.

The sleeves and followers dimensions and tolerance are detailed in the workshop manual. The use of a good quality micrometre and bore gauge is required to check them. The followers wear into a barrel shape and the sleeves wear into an hour glass shape so you need to measure then at top middle and bottom to check the wear.

Provide the sleeve wear is not to great the sleeves can be honed and over size followers fitted which are available from the usual suppliers.

I cant really comment of whether it safe to continue using the engine until the source of the noise is better identified. if its a small amount of excessive wear in the sleeve and followers then continued use is generally not a problem

cheers
Rohan

[alan.barker]

I would check first Exhaust flange gaskets.
That means removing exhaust studs using 2 locknuts to unscrew. then you can slide each gasket out to check if they have been leaking.
I've had this problem several times.
Alan

[LCRJ]

Hi Rohan and Alan,
Thank you for your advice.
Yes, there was no sign of an exhaust leak but I too suspected a leaking exhaust manifold gasket.
I tightened the bolts more but the sound did not change.
Today I recorded the sound on my iphone for reference and posted on Youtube.
The links as follows,

1，Recorded the engine starting and warming up from the front(4min30sec until it warms up).
https://youtu.be/T8JZQq3mdZ0

2，Recorded idling after driving from the front
https://youtu.be/XRjZ9JC_3Ts

3，Recorded idling after driving from above cam cover
https://youtu.be/eKYnooTJ-IM

What do you think? Is the cam follower the cause?
Apart from the noise, the engine is in good condition, so it is difficult to decide whether it should be overhauled immediately.
I would appreciate any advice from your experience.

Kind regards,
Hiro

[512BB]

Your recordings sound like 80% of twin cams running today. Most tick away like yours quite happily, and will continue to do so for many a thousand mile, but I do not believe you are any nearer finding out if it is a bucket / sleeve wear problem, or a manifold crack problem. Personally, I think it is the former.

I had a car exhibiting exactly that noise. As the head had recently been expertly rebuilt, ahmm, including having new sleeves and buckets fitted, I removed the manifold and there was the problem, a crack in the manifold where one of the tubes joined the flange. Welded up, no more tapping.

If you remove the cam cover after the engine has been run up to temperature, then cooled down a little, then remove a cam. Get hold of one of the buckets with 2 fingers, leaving the majority of the bucket in the sleeve. If you can rock the bucket from side to side AT ALL, that will be a source of ticking when the engine is running.

On a newly built engine that has had new sleeves and buckets fitted, the buckets will almost be an interference fit in the sleeves, if honed correctly, and there will be no ticking.

I hope that is all ticketyboo understood

Leslie

[alan.barker]

The only way to know if it's the exhaust gaskets is to remove them. Been there done it during my 48 years of TC tinkering.
Hanging on a spanner will not change things except strip a thread on a brass nut (i hope your using brass nuts).
Alan

[LCRJ]

Hi Leslie,
Thank you for your advice. I will check it then decide to do what I need.
If you know, Could you tell me the best parts suppliers?
Kind regards,
Hiro

[LCRJ]

Hi Alan,
Just in case, There are no sign and stains from exhaust gaskets leaks.
On your case did same situation also?
Kind regards,
Hiro