Main gears

[Tiger]

Having done some short runs now.
It is evident that the mesh between the crank/cam gears is too loose .
Help please about the best way forward.

[Ruairidh Dunford]

I use a stock of these to mix and match to obtain a better mesh.

I can help, but I will need the crankcase, at the very least.

[Chris KC]

You mean the timing gears? What is driving you to that conclusion?

I venture that the optimal backlash (measured with feeler gauges) is about 3-4 thou minimum. A bit more is not massively harmful, but increases noise.

David Dye makes new gears.

I had trouble on my RP's engine as everything I tried was too tight, or a massive gap. In the end I paired up two random gears which were in good shape and gave a suitable amount of backlash - hasn't failed yet.

[Tiger]

Thanks for the quick replies gents.
The main reason is very noisy tickover stops with slight increase in engine speed.
Also very poor ability to climb small rises.
Also if you stop the engine at a point when no valves are working a degree of play can be felt at
the cam pulley difficult to explain the amount of play but a definite click heard.

[Chris KC]

If in doubt I'd suggest to have the front cover off and check the gear backlash (through 360 degrees) - cold - with feeler gauges.

Valve train noise at tickover isn't necessarily something to worry about in itself, but if you suspect something's wrong it might be wise to check.

[David Stepney]

Thanks for the quick replies gents.
The main reason is very noisy tickover stops with slight increase in engine speed.
Also very poor ability to climb small rises.
Also if you stop the engine at a point when no valves are working a degree of play can be felt at
the cam pulley difficult to explain the amount of play but a definite click heard.

Are you sure it is the timing gears? I appreciate that it is nigh on impossible to diagnose noises without hearing them, but my engine is noisy on tickover and quieter at higher engine speeds. I suspect that this is due to rear main rumble but I shall live with it given that my car generally runs very well.

Given that the car appears to lack power, I repeat what I said on your 'Propshaft Problems' thread regarding ignition timing. I presume that your new distributor bobweight springs have arrived and are fitted. It may be worth checking the timing with a strobelight. Having little experience of Rubies, I do not know how difficult it is to gain access to the flywheel timing marks, but temporary marks can be made on the camshaft pulley. With a high compression head, you should get about 16 degrees of advance at the flywheel or 8 degrees on the camshaft pulley. Given that you are running a low compression head, it might wear anything up to 20 degrees at the flywheel (10 degrees at the camshaft pulley) before the engine starts to sound harsh.

Just as a quick guide, 16 degrees at the flywheel equates to about 1 1/4 ins at the flywheel rim and 20 degrees to about 1 9/16 ins

[AustinWood]

The cam gears are very noisy if there is too much endfloat. Difficult to assess with a complete engine.

[Tiger]

Cam endfloat was set to near zero when I part built the engine.
Now Fitted new advance springs with original good weights.
I shall be trying to set up for a strobe light
Also complete a further road test.

[stuartu]

Dynamo end float? Noisy at tickover and certainly won't improve ignition timing accuracy. Can be investigated by removing tin plate on dynamo housing and loading the end of the dynamo shaft at tickover with something pointy.

Regards
Stuart

[Howard Wright]

Cam endfloat was set to near zero when I part built the engine.
Now Fitted new advance springs with original good weights.
I shall be trying to set up for a strobe light
Also complete a further road test.

Hi Tiger

I hope the end float was not zero!  I understand that oil has to pass through the cam bearing in order to lubricate the timing gears. Zero end float would prevent this and it would take no time at all to ruin the gears.

Cheers

Howard