Timming

[stevewright]

Afternoon everyone. Got a lovely little problem on my 1954 colt. Out on a ride last week, and it suddenly spluttered to a stop. After much investigation, the points cam appears to be 90° out of position.. anyone got any idea on what's broken. I've had the cam off, and the advance/retard mechanism, and it all looks good. But something clearly is not.

Has anyone else experienced this.?

[will_curry]

The auto advance unit is a tapered fit into the end of the camshaft and there is
a small key formed on the end of the auto advance unit to locate it correctly. If the
key isn't located properly when the engine is assembled or the key is damaged it is
possible for the timing to slip just as you describe.

[stevewright]

Will_curry,
I've Checked that, and it all looks good. Everything is points to something maybe further inside the engine.

[will_curry]

That's interesting. Anything else I can think of will have disturbed
the valve timing too. Any sign of that happening?

If it has disturbed the valve timing the next thing I'd check is the fit
of the crankshaft pinion on the mainshaft. If that's OK we're into
the realms of the really unusual: cam pinion turning on the camshaft
or maybe even the mainshaft turning in the flywheel.

Do please keep us informed of what you find.

[stevewright]

I know. To be honest I'm not looking forward to what I find. I was hoping it was the location pin on the advance unit broken. Everything on the engine is as it should be. Valves, compression, electronics.. I can't remember how the drive all connects from the crank from when I rebuilt it about 5 years ago.

[will_curry]

Another though - can you set the ignition timing correctly when the auto advance is properly
located in the camshaft?

[stevewright]

No. There is not enough movement in the points plate by a long way. When you set the piston in the correct position, the points cam is already half way through its 'opening' face. At this point, The opening point of the cam should be at approximately 12 o'clock. But it now sits at 9 o'clock..

[will_curry]

That's the indicator that the timing cover is going to have to come off.

Something's moved and the next thing I'd try is the crankshaft pinion
fit on the mainshaft.

[stevewright]

That's next move. But even then, shouldn't the piston have fouled the valves..? As the valve timing is a direct toothed cog drive.

[will_curry]

Not necessarily. With a bit of luck nothing touches and hopefully you've been lucky.