Camshaft wear

[Henry Harris]

I am experiencing what sounds like a clattering sound from the engine at exactly 3,500 rpm in any gear. On further investigation it sounds louder than pinking, but the engine is not pinking. Even further, the clattering is there but not as pronounced at higher revs. Nothing else appears wrong with the engine. The engine pulls fine all the way up to whatever I want well above 3,500 rpm. There is no blue smoke, neither any other loss of oil other than sump seeping and I am not losing any water.

Also, occasionally for less than a second there is the similar clatter that then disappears immediately at start-up

My thoughts are that this maybe the typical Rover V8 camshaft wear. Are there any thoughts? It is just annoying me, on the other hand, if it ain't broke then don't fix it!

Thanks in anticipation.

Edited by Henry Harris on Thursday 25th July 14:52

[JVaughan]

What is the mileage on the engine ? IIRC camshafts usually show signs of wear after 60k

[Henry Harris]

Engine mileage is unknown. The car has done just under 70,000. The engine does not have the original block. It is now a cross-bolted 4.6 litre. I have not been able to find any detailed history.

[pwd95]

Similar symptoms on the Griffith forum a while back. Turned out to be small end wear. Put it on the rollers. The shape of the curves will show up any cam wear, especially if you know the spec of the cam.

[Danny Hoffman]

Is it flapper or hotwire injection?

When my flapper's cam was very worn the variation in suction at full throttle caused the flap to bang shut.

[Number 7]

Danny Hoffman said:

Is it flapper or hotwire injection?

When my flapper's cam was very worn the variation in suction at full throttle caused the flap to bang shut.

Carbs

[Henry Harris]

Thank you everybody for posting.

I forgot to mention that my car has a multi-spark ignition system, Edelbrock inlet manifold with a four-barrel Edelbrock carburettor.

[Number 7]

A compression test might give a clue as to where any problems are.

[Danny Hoffman]

Henry Harris said:

Also, occasionally for less than a second there is the similar clatter that then disappears immediately at start-up

This does sound like a hydraulic tappet pumping up. What oil are you using and is it changed regularly?

[Jack Valiant]

Henry

Get some 20/50 Valvoline into the car matey and recheck

Chris

[V8 Fettler]

The rattle at 3500rpm, is it under load or no load?

[Henry Harris]

Thanks again everybody.

I have tried different oils. Currently Mobil 1 10/60.

The clatter is most pronounced when moving under load - as an example at an indicated 50mph in 2nd gear at 3,5000 rpm, but can just be heard when the car is stationary.

[Danny Hoffman]

Under load could be bearings. It is definitely a clatter rather than a ticking which could be an exhaust/manifold leak?

[adam quantrill]

Henry Harris said:

... 2nd gear at 3,5000 rpm....

Yes, I think you're caning it a little ;^)

No but seriously if the cam is worn then you get less noise usually because the valves are moving less. Agree with above: might be too-thin oil or a tappet. On the other hand at 3500 rpm the oil pressure is well up.

With the carb on there you should be able to get both rocker covers off easily so I would turn the engine over on the starter while taking a good look at the rockers moving, plus you could then repeat by hand (15/16" socket on the front pulley nut) and measure the lift on each rocker. If there's obvious wear one won't be moving!

[V8 Fettler]

Does a 4.6 have hydraulic tappets? Pumping of the tappets usually takes a few seconds from cold, and that's it until it's cold again.
Perhaps start with the easy things Henry, change the oil and filter, check exhaust manifold fixings. Must be a noisy rattle if you can hear it above a TVR V8! I occasionally get pinking on hot days uphill with a passenger and lower octane, but that's at 4k(ish) rpm and then ease off. I would assume that the pinking would get worse at higher rpm, although it should reach a point where it stops due to piston speed. No pinking on cooler days with higher octane up the same hill with a pass.

Adam, is it possible to view valve operation through the plug 'ole? Would eliminate the need to remove rocker covers.

[adam quantrill]

Not easily, maybe with an endoscope. But removing 4 spark plugs takes longer than removing a rocker cover.

[Wedg1e]

adam quantrill said:

With the carb on there you should be able to get both rocker covers off easily so I would turn the engine over on the starter while taking a good look at the rockers moving, plus you could then repeat by hand (15/16" socket on the front pulley nut) and measure the lift on each rocker. If there's obvious wear one won't be moving!

You can't reliably measure the valve lift this way as the lifters will drain down with no oil pressure. You're right that you'd spot any not moving at all, but you'd probably be able to tell that by the running.

[adam quantrill]

Yes I obviously mean gross problems rather than exact valve lift down to the nearest millimetre.

But if it's clattering - there's a gross problem - probably.

[Henry Harris]

adam quantrill said:

But if it's clattering - there's a gross problem - probably.

I am not sure about a gross problem, as apart from the noise, the car runs perfectly.

As I wrote before, if it ain't broke, don't fix it. The noise is a little annoying and I want to fix it.

I will probably go down the route of a closer camshaft inspection and if necessary replace it with a hotter one. By the way, the hydraulic lifters are fine and the cam followers were replaced last year.

[Jack Valiant]

Henry, if you are convinced its the cam then the best thing is to drop the oil and take the sump pan off with a good light you can have a good look at the cam lobes for wear fella. Worth a new sump gasket and some oil for piece of mind??

Chris