Valve clearances opening up

[promotor]

Ok so have done a more complete and accurate measure of valve clearances. New feelers and engine stone cold.

Exhaust valve clearances are all pretty spot one 0.010". Inlet valves are all at 0.005" appart from one at 0.004"
These are pretty much spot on yes?

So wonder where the tapping noise is coming from.

The "screw driver" stethoscope makes me think it is cam related and I think the periodicity is half engine speed (but need to check) which confirms this. I suppose I could just not be used to the tappet noise of these twinks.

Tim

Loose cam follower(s)?

[2cams70]

These are ancient engines. It's not realistic to expect them to be as quiet as something more modern. I'd just run it as is and monitor how it goes - i.e the oil consumption, coolant consumption, oil pressure, performance, temperatures and smoke from the exhaust. If those factors are OK, clearances are OK and the noise isn't getting significantly worse over time I would not be losing any sleep.

By the way on the subject of light tapping noises if your piston pin clearances are too large this can also make a sound similar to tappet noise.

[shynsy]

Ok so more info.
Started the elan from cold and all sounded pretty quiet. Let it warm up a bit and gave it a little throttle and the knocking was back. Have narrowed it down to number 3 exhaust valve. Checked clearances (now warm engine) 1,2 and 4 exhaust valves around 11 thou number 3 valve 16 thou. Guessing this is the culprit. Guessing this suggests either the valve or the tappet is sticking?
Tim

[2cams70]

It’s anybody’s guess what could be wrong but valve clearances should not change within a very short space of time after running the engine. You need to dismantle more - i.e remove cams and followers to have a look see. It could even be (hopefully not) a loose valve seat which can have serious consequences and should be immediately attended to. It’s just pulling things out of the air until you physically inspect further.

[shynsy]

It’s anybody’s guess what could be wrong but valve clearances should not change within a very short space of time after running the engine. You need to dismantle more - i.e remove cams and followers to have a look see. It could even be (hopefully not) a loose valve seat which can have serious consequences and should be immediately attended to. It’s just pulling things out of the air until you physically inspect further.

Totally agree. That's my plan. Cam off for a look and if that doesn't show anything obvious, head off.
Tim

[shynsy]

Hi folks.
Have pulled the exhaust cam.
All looks good around exhaust 3 valve. Nothing that I can see that is obviously wrong.
Collets in place. 80 thou shim. Shim surface looks good.
Tappet moves freely in its bore. Rotating and moving in and out.

Only thing i noticed is Just a tiny bit of resistance before it touches the valve head when I have no shim in place (simulating the first 80 thou of movement in normal use). I don't feel similar with number 4 exhaust. Resistance isn't too much though.

Thoughts?
Tim

[shynsy]

Photo of valve head and collets

[promotor]

Photo of valve head and collets

That follower is toast! Looks like it has been extremely tight.
Also, has the underside of the follower been catching the top of the retainer rather than the retainer and the valve shim making contact?

For me, that'd be a head off job, valves out and full inspection. 1st job would be to check cam follower clearances and wear, but after that the whole setup would need checking. Don't leave anything to chance.

[rgh0]

Agree that follower is absolutely no good. Have you measured the clearance in the sleeve for each follower and looked at their surface condition. They should be highly polished with no significant marking. You also need to check top , middle and bottom of both followers and sleeves as the followers wear into a barrel shape and sleeves into an hour glass shape. Worn sleeves and followers will result in tapping as the followers rock in the sleeves even if valve clearances are Ok. The tolerances and clearances are shown in the workshop manual and you need good quality micrometres and bore guages to measure the components to the required accuracy.

cheers
Rohan

[Lotus54]

Decades ago, when I had my Lotus Cortina- the seats were ground/worn enough that valves had come up. So shims were very, very thin and the spring retainer would hit the follower.

I could not tell from picture, but any chance it is hitting?

[rgh0]

80 thou is getting close to the lower limit, depending on the retainers, valve tip length and followers used it is very possible for the follower to contact the retainer

The marks on the top of the follower in the photo are unusual but may be caused by the lighting angle in the photo

cheers
Rohan

[shynsy]

Decades ago, when I had my Lotus Cortina- the seats were ground/worn enough that valves had come up. So shims were very, very thin and the spring retainer would hit the follower.

I could not tell from picture, but any chance it is hitting?

I think this had happened previously with this head but it was resolved by the rebuilder and the shims are now 80 thou.

How would I know the retainers were hitting the follower?

[shynsy]

Sleeves also look a little gnarley.
Guessing the plan should be to remove rhe head and get someone to fit new sleeves and followers. I live 20 mins from wilcoxes, I take it they would be recommended.
Tim

[promotor]

Sleeves also look a little gnarley.
Guessing the plan should be to remove rhe head and get someone to fit new sleeves and followers. I live 20 mins from wilcoxes, I take it they would be recommended.
Tim

The marks look like rust from being stood - maybe that is part of the issue? There may be other issue at play here though.

Depending on size / wear you could get the sleeves bores out rather than replaced, but that puts you down a possible route that may not be rectifiable with further oversize followers if you end up at the top end of the O/S's available.
I think +0.005" followers may be available from QED but don't show on their website. Best to call them,
To me honing is not the solution, only boring them out to cut a nice round hole.

It's certainly worth a call / email to Wilcox - I don't think they do the work on followers themselves but use an engineering firm to do it but will have been through this numerous times so will be able to advise.

[shynsy]

Probably a stupid question, but can you not get the sleeves removed and new sleeves fitted?
Tim