B40 clicking

[Stubaker58]

Having fitted a thicker head and base gasket to my B40 the piston no longer kisses the head at TDC but with the rocker box fitted a worrying clicking is still there.
There are two clicks, one for the inlet valve the other for the exhaust. It happens as each valve passes its fully open point ie just at the pint the valve starts to close.
I'm beginning to think it's something to do with the cam/cam followers.

Has anyone had a similar situation?

Any suggestions for what to do next?

TIA

[limeyrob]

Have you checked the piston / valve clearance - some plasticine on the piston?
Are the guides new, could the valves be sticking?

[Ian C]

I had a similar issue on my B44. The reason was that the flange on the new top hat cam bush in the inner timing cover was just slightly too thick and was causing the foot of the inlet cam follower to bind. I machined off a few thou (can't remember exactly how much) and issue was cured. HTH

[DAVE BRADY]

Hi,

Is this clicking only when turning the engine on the kickstart or when it is running?
It could be backlash in the timing gear. I think that as the cam passes fully open instead of the cam compressing the valve spring the spring is now pushing the cam.  The point of this change will result in any play in the timing gear to 'move' from one side of the teeth to the other with a click in worn gears.
With the engine running the sound will become less audible.

Dave.

[Stubaker58]

Thanks guys.

I haven't tried to start the engine yet, I've been turning it with a spanner on the drive side nut. It was in the frame but is now back on the bench.

I don't think the valves are sticking (but what do I know, I'm really a Bantam man!)

Backlash in the timing gears as described is a distinct possibility, thanks for the clear explanation.

I think I'll get the timing side apart and have a look.

[rhyatt]

does your engine have the valve lifter arm on the rocker cover, is that internal mechanism catching anywhere/anything?

[DAVE BRADY]

Hi,

On the distributer engines you can check the backlash by removing the outer timing side cover and seeing how much the nut on the timing gear can be moved. There will be some movement but unless it is more than few degrees it will not be a problem.  Once the engine is running and oil is getting on the teeth it will reduce and become quieter.
The side point engines need a bit more stripping to get to the gear but it should be possible check it through the centre of the points.
With both valves closed and the advance/retard held open or closed to prevent movement, the centre screw can be used to feel any backlash.
 
Dave.

[rhyatt]

i'm wondering if the clicking is the tappet/cam follower "dropping" back onto its cam.
are they smooth in operation , not dry after rebuild.
pour oil into the valve cover window and let it flow down and lube the followers in the little guide holes

[V500]

Hi,

Is this clicking only when turning the engine on the kickstart or when it is running?
It could be backlash in the timing gear. I think that as the cam passes fully open instead of the cam compressing the valve spring the spring is now pushing the cam.  The point of this change will result in any play in the timing gear to 'move' from one side of the teeth to the other with a click in worn gears.
With the engine running the sound will become less audible.

Dave.

+1 for this. It's very noticeable on some engines when turning them over.

[Stubaker58]

Outer timing case off and cam nut jerks in time with the clicking.

Listening via a long screwdriver gives a loud click on the cam housing.

Mystery solved, thanks guys.