Top End Noise from Engine - Tappets? Tach Generator?

[kingzetts]

This past winter I applied extra sound-deadening to the centre console which has substantially quietened down on whine from the gearbox.

However, it has now thrown into greater prominence another noise which was there before but which is now more noticeable and I am simply pondering what it is most likely to be and whether to tackle it this coming winter.

Anyway, the noise can best be described as a relatively high-pitched whirring noise which follows engine RPM rather than road speed/prop shaft RPM and persists when coasting at speed with the clutch disengaged and the gearbox in neutral but keeping the engine revs up. From the drivers seat it gives the impression of coming from the front bulkhead area behind and above the bellhousing, while with the bonnet open it appears to come mainly from the rear of the cylinder head area.

From this I conclude that it is not related to the gearbox or to the speedometer drive or speedo, but it sounds a little too high pitched to be simply tappet noise which in my (albeit limited) experience tends to be a rather deeper noise.

Initial thoughts are the cam-driven tach generator, or maybe it simply is tappet noise. Anyone care to add suggestions?

[Heuer]

Tach generator would be the first and easiest thing to swap out. Avoid the repro ones though. Try a s/h one from Wilkinsons, Ken Jenkins, Ken Verity or Richard Smith. There is an App on my Android phone I use and it works very well - Superhero Hearing - which when used in conjunction with headphones acts like a very sensitive stethoscope. No doubt there is a similar app for iPhones as well. Allows you to pin-point noise sources very accurately.

[ALAN COCHRANE]

John

Get yourself a mechanics stethoscope. I bought one recently off Ebay for ?5 and it's brilliant at pinpointing untoward noises which is just as well as I seem to be having a steady stream of them at the moment.
I'd agree with David on the Tach generator being the problem though.

Alan

[kingzetts]

The two of you have reminded me I have one of those electric stethoscopes with a metal probe, amplifier and set of headphones which I had forgotten about stashed away somewhere in the toolboxes. Time to dig it out and see if I can pinpoint the noise.

Cheers guys.