Clicking/tapping troubleshooting

[NOW]

Hi everyone, sorry for asking for more advice but at the moment I am a bit of a novice!

Recently I've had a tapping noise coming from the front of the engine, it increases with the engine as if it is in time with it. It's not especially loud, and performance is unaffected by it.

I've heard that the problem could be anywhere from valve clearances to a loose inlet manifold to a carb air leak, the engine was rebuilt recently so I doubt it's this, although it could be that this is the sign of it's first service! I don't want to disassemble the engine if I don't have to, so where can I start in terms of troubleshooting? Someone suggested holding a screwdriver to where the noise is coming from to use it like a stethoscope, others have suggested holding something over the exhaust for a better listen.

Where can I start, and how should I trace this problem? Thanks in advance :)

[jetblack]

Check for a leak around the front downpipes.

[Davez29]

Hi. You appear to have read up on this sort of noise. I would check manifolds as suggested as thats the easiest thing to check, chances are it is the header clamps loose and hopefully not tappets. Did you use new crush gaskets after you engine rebuild? When i add new crush gaskets i also put a layer of exhaust paste on, mainly to keep them seated and to help seal.. Thats just my preference tho'.

[NOW]

I'll be checking the manifolds later today, looks to me like a fairings off job

[blueflag]

I'd bet it's a header leak too.....

[Wozza]

Just in case, does it sound anything like this?
http://www.youtube.com/watch?v=UNzDTGteMQI

[Hutch58]

Definitely check the header pipes. I had the same problem, turned out to be a small rust hole in the header pipe, just where it pushes into the head. On a quick visual it was hidden by the clamp. Only found it when I dropped the header pipes. Had it welded up, noise gone.

[BerryBlade]

Possibly could be timing chain needs retentioning? I have heard they go alot on the grey 400s

[gullarm]

Possibly could be timing chain needs retentioning? I have heard they go alot on the grey 400s

What timing chain? There isn't one!