Do wearing Cam Journals make a noise?

[oldtuckunder]

Ok bit of a long shot, but trying to decide how far I go with this winters engine fettle.

 

Its been completely stripped and rebuilt a few times in recent years (mainly due to big end failures, but that's a long thread, and we think the problem(s) are now resolved) At the end of last season (having survived) it was fully stripped and everything was perfect, so just re-assembled with new shells and rings (because why not). It has been faultless this season and the Millers Oil analysis that has just come back is very close to last years.

 

So this winter rather than engine out and strip I was hoping to just get away with head off for a look see and relap the valves.

 

But there is a small rumble noise at tick over which if I had to guess is coming from top rear of engine, however one further problem is that the collector boxes on the headers have holed again (they have had a hard life and will be replaced this winter) so its a bit hard even using a listening bar to decide what or where the noise is coming from. It could actually just be a blowing exhaust resonance. If I bring the revs up it disappears but maybe mainly by increase in exhaust noise.

 

So just wondering if anyone has experience of what a wearing cam journal sound like, or if there is anyway to test without stripping engine. Its a 6 pot with the cam running in the plain block journals no bearings. This is just a rumble, no tapping, no knocking, just a just gentle rumble vaguely similar to a wheel bearing.

 

Of course it would make sense to strip off the old headers, fit the new ones, and see if the noise is still there, but I'd rather not do that as its a fair amount of work on the Vitesse and as the head is coming off anyway........

 

Any bright ideas?

 

Its probably a complete red herring as if there was any wear to the cam or the journal in the block I would expect a significant Increase in Fe (iron) trace readings in the oil analysis which whilst this year are 28ppm up only slightly on last years 19ppm. But you know what its like, get a slight suspicion and.................

 

Alan

 

 

 

[boxofbits]

Hi Alan

 

Wearing lobes dont normally make a noise unless really excessive , though you could get a loose tappet but again not normally a rumbling noise.

 

I have tested for tappet noise by inserting a feeler guage with the engine running ( great care here obviously needs to be taken), or temporarily tighten the gap out, or it could be piston slap. you've re-ringed the Pistons so you might get a little noise from the bores, but if it's not using oil you may not need to worry too much.

 

Kevin

[oldtuckunder]

Hi Kevin

 

Sorry wasn't clear, I didn't mean the lobes wearing, virtually no tappet adjustment has been required, and I can measure lobe shape using a dial gauge. I meant the journals where the cam runs in the block, in the 6 these don't have bearings as standard, the cam runs straight in the block material. I know that at sustained high rpm's they do wear/fail, and whilst I do use revs approaching 7k its normally only for a few seconds at a time.

 

Alan

[Peter Cobbold]

Alan, You give it a hard life with high rpm standing starts.....so maybe thrust washers? Peter

[TriumphV8]

Cam does not make a noise.

Normally the front bearing wears most due to chain tension under load.

 

Sometimes the inner bearing fails completely and eats the cam and welds together.

Wear in the cam area normally is noticed by dropping oil pressure long before

they make noise.

 

I would look at the clutch or at the front pulley.

[Guest ntc]

Remove fanbelt and try again.

[Nick Jones]

As Andreas says, wearing cam journals/bearings affect oil pressure. If wearing significantly (rare unless using mega springs or the springs are getting coil-bound) then tappet gap will be affected.

 

Possible noise culprits

Water pump / dynamo/alternator - run without belt to test.

Timing chain tensioner

Oil pump/distributor drive or the distributor itself.

 

Nick

[DaveN]

A constant rumble does point to something rotating. ...... rear main bearing??

[oldtuckunder]

Thanks guys, some good inputs, zero oil pressure problems, doesn't sound like cam then. I'll run some further tests based on input and report what I find.

 

Alan

[graeme]

Hi Alan,

 

Could it be the input bearing in the gearbox starting to fail? You said it sounds like a wheel bearing and the only ball bearing near the rear of the engine is in the gearbox.

 

Try using the clutch while listening and see if the noise changes.

 

Cheers

Graeme

[oldtuckunder]

OK done some checks and I think maybe I was talking myself into having a problem.

 

Disconnected fan belt, no difference so not Water Pump or Charger

Pushing Clutch makes no difference (was wondering about clutch release bearing)

Had a good listen around distributor drive (with borrowed Stethoscope) and apart from gentle ticking of points nothing.

Checked Crankshaft end float and whilst not precise, minimal, but will check again and measure when all the gubbins is out of the way.

 

I'm beginning to think its actually an artefact of the header blowing, its at cam speed (hence my original thought) not engine speed, which would tally if its originating from the collector box on one header (i.e every second combustion) Played with gently increasing the revs and it rises in line sounding gruffer as it rises until around 1500/1800 where the blowing collector overrides other audible noises. Collectors are hidden down below heat shielding so its all a bit muffled and not easy to discern what direction sound is coming from, and in the absence of locating a source listening on the head or block, I think I'll opt for paranoia being the cause :-)

 

So took it for a 20 min pleasure drive (don't normally do those, road miles are normally testing or on way to events) late November sunshine, glorious straight 6 howl up over the Malverns, smile making, and back and in to the Polycoon, heater on, start planned top end strip in the next day or so.

 

Thanks for the suggestions, if I find anything I'll let you know, and further suggestions always welcome.

 

Alan

[oldtuckunder]

Thanks to JohnD suggesting else where about buying a proper stethoscope, I bought a mechanics set with a long metal probe on it, and whilst I'm long used to using a metal bar or long screwdriver to listen, the difference is amazing with the proper tool!

 

Bonnet/Front End! off and all heat shielding removed, and already the rumble sounded different, but still there, checked every where and all sounds crystal clear and fine until I got to the headers, one just background engine noise (amazing but points clicking travels almost everywhere) the other nice gorgeous rumble exactly what I was looking for. Must just be a peculiarity of the break which I can't see as its between the two collector boxes, that makes the blow sound like a rumble.

 

Anyway don't think I'm looking for anything sinister any more, will see when the head and new headers go back. Now I have to decide if new Stainless Headers need wrapping or some form of Snake Oil coating

 

Alan

[Guest ntc]

Bet you fitted the gasket dry?

[oldtuckunder]

Hi Neil

 

No don't have any! but have seen what you describe.

 

My problem is that the old mild steel collector boxes have started disintegrating, had to have them off once during the season and patched up, but are going again. They have done well so I'm not complaining.

 

Alan

[Dave Herrod]

Bet you fitted the gasket dry?

Neil,

 

what do you recommend for manifold gaskets?

 

Dave