Tap tap tap

[Robbie693]

Another worry:

I have a pronounced tapping from the top end as if one of the valve clearances is too big. Why would only one make a noise? I thought they get tighter as they wear and should wear evenly...

I don't think it was doing this when I bought it but I may be wrong, anyway a little history of the car may help:

The engine was rebuilt in the early 90's by the owner at that time who used an apparently well known race engine specialist (I forget the name) for the machining work and was given help / advice by Peter Day for the re-assembly.

The car was then sold to another guy who did about 1500 miles the whole time he had it (almost 15 years). There are a few MOT's missing so I assume the car was off the road for some period too.

I bought it from a dealer around 18 months ago and he had put about 300 miles on it himself, since then I have done around 1000 so the car has probably done about 3000 miles since rebuild.

[steveww]

Why not just get out the feeler gauges and check the clearances?

[Robbie693]

I will when I get a chance - got to try and sort out the over-fueling problem first (see Rough running post).

I was just wondering if there was anything else I should look for at the same time as checking the clearances?

[steveww]

A small blow from the exhaust manifold (headers) can sound like a tappet clicking. Check that the manifold is tight if the clearances are fine.

[Frank Howard]

My car has had the same problem since I purchased it 20 years ago. I figured that a rebuild including a valve adjustment would take care of it, but it didn't. It still makes the tappet clicking noise to this day. I too would be very interested to find out what it is.

[1964 S1]

...timing chain tensioner? I'd monkey with it and see if it changes the tap.

[JJDraper]

My +2 has a distinctive light tap, again as if one tappet is wide. It has made this noise ever since I first got the car, some 50k miles ago. The head was rebuilt by QED with new cams & valve gear and that made no difference to the noise. It seems to be more pronounced at light throttle openings and disappears if you open up. Classic wisdom says little ends, but I can't believe that. On my recent thrash in France, I had a lot of time to consider/worry where the noise eminates from, as my passenger remarked on it as well (in 15 hours driving you exhaust many other topics of conversation and you start mentally ticking off the things that could go wrong!).

I have come down on two possible sources for the noise - Fuel pump, as this is close to the bulkhead and any noise would get through easily, but this does not explain the throttle load aspect. The other major suspect is the vacuum none return valve chattering. This is my personal favourite, although I seem to have two vacuum NRVs, one for the lights and one on the servo line.

The upshot is that I have learned to ignore the noise (at least on my car), as it doesn't seem to get any worse with age, or oil changes. I suppose I , could try running with the vacuum outlets blocked, but frankly I try and leave things alone!

Jeremy

[ppnelan]

Has a tappet sleeve twisted round in the head
Are the valve springs seated properly on their 'washers'
Has a valve guide come loose or 'slipped' upwards so it contacts the retainer
Yes, it CAN happen...

Matthew

[Robbie693]

I have had a new centre pipe on the exhaust which took a bit of bashing to get the joints together, so I'll check the manifold hasn't come loose.

The noise is louder when I have my head under the bonnet, which makes me think top end rather than bottom. Last time I had the cover off (stupidly didn't check the clearances then ) I noticed one of the inlet cam lobes had brown staining on the base side. Couldn't tell if it was rust or what but it didn't wipe off...

The tappet sleeves - how do you tell if they have twisted around?

[rgh0]

A top end tapping noise is often a loose bucket in the guide sleeve. The buckets wear barrael shape and sleeves hour class shape and the bucket rocks and taps on each valve actuation. The tapping can change with engine tmeperature as oil viscosity changes and clearances change with temperature and often disappears at high revs.

The risk is that if the wear gets bad enough the bucket can tilt and jam in the sleeve resulting in major damage when it breaks.

If valve clerances are OK and you are sure the noise is still coming from the valve gear then pull the buckets and check clearances carefully.

cheers
Rohan

[Robbie693]

Thanks Rohan,

How should I measure the buckets and sleeves and what should the measurements be?

[rgh0]

Specs for tolerances are given in the workshop manual. You need a bore guage for the sleeves and micrometer or good quality vernier calipers for the bucket. Check top, middle and bottom of each to look for barrelling and hourglass wear. You need in spec clearances over the whole length to eliminate the tapping.

You will often find a tapping bucket has in spec clearances in the middle but wera top and bottom of the bore and bucket is above tolerances leading to the rocking effect and tapping noise

cheers
Rohan

[rjaxe]

Interesting thread as I am also pondering over a similar tapping sound from the valve gear of my +2 myself. I had checked and adjusted all the valve clearances so they were all mid tolerance but dissapointingly this did not make any difference to the noise. I have since completed a 1300 mile round trip in France with no problems, the noise did not get better or worse.
The tapping is consistently cyclic, rising and lowering in volume roughly every 20/30 secs. I am convincing myself that a cam bucket is slowly rotating and the valve clearance changes as it goes round. This may be a fanciful theory as I am not even sure the bucket rotates. Though if so this would point to a dodgy dimensioned bucket or uneven wear. Looking at the parts there does not appear to be any wear. Next time I have the cam cover off I will make a point of rotating the cam followers and check if the valve clearances are affected. I might also be able to get a DTI on the cam follower face and rotate them in-situ to check for squareness.
I shall be interested to know if anyone resolves this issue.
Richard

[ppnelan]

Richard, yes, the buckets should rotate to even out wear. That is why the cams push off-centre on them.

Robbie, if you have an S/E or Big Valve head (I think?) it will have semi-circular cut-outs milled into either side of the head & tappet sleeve to provide clearance on the (higher lift) cams. You can tell they have rotated if the cut-outs in the sleeve do not line up perfectly with those in the head. If they rotate far enough (when hot), the sleeves may just about contact the cams, which can make a tapping sound as it machines metal away...

Matthew

[Robbie693]

Thanks all - that gives me plenty to check, when I get chance. I'll report back with the findings.