Ignition timing

George Evans · Joined: 20 Sep 2017 Posts: 5

I recently fitted a new cylinder head to my 4/1/4 Derby Bentley and I cannot start the engine.
I did not remove the distributor. I did use the starting handle to raise the pistons for cleaning and setting the valve clearances after the head was fitted.
I checked that the coil and spark plugs were healthy and that petrol was being delivered.
I checked the ignition timing as follows:-
I turned the engine through a rear wheel until No.1 piston was at TDC which I
checked with a bent copper rod. The inlet and exhaust valve were both closed and the points opened as the rotor was approaching the No.1 contact in the distributor cap.
The only mark visible through the inspection cover on the bell housing is a
line etched on the clutch housing cover.
This line does not seem to line up with the pointer at TDC or anything
relevant. All other timing marks are hidden on the flywheel.
I would be grateful for any advice.
Thank you

John Robins · Posted: Thu Oct 18, 2018 9:49 am Post subject:

Sorry to be so simplistic, but did you actually see a spark at the appropriate plug at the appropriate time?

Christopher Carnley · Posted: Thu Oct 18, 2018 12:53 pm Post subject:

To add to the previous, is the condenser OK, are the plug caps on the appropriate spark plug?
Is the distributor cam and rotor drive firmly screwed down, as it is on a taper for adjustement?

When a clutch was changed the the previous marking were scratched into the cover, just check that it is not 180 out, not that it hold be.

George Evans · Joined: 20 Sep 2017 Posts: 5

I did not actually check the spark at each appropriate plug. I will do so.
I have fitted a new condenser and the plug caps are fitted correctly
I will double check the distributor cam and rotor drive but I am sure they are secure.
I will determine a line at 180 degrees to the existing mark and see where I am with that.

John Robins · Posted: Thu Oct 18, 2018 4:31 pm Post subject:

Before doing the technical stuff, just flick the points to see if you get a little spark across them. 12V wires to the distributor have been known to go open circuit inside the insulation when shaken about, especially old ones. It’ll only take half a minute and at least you’ll know that the low voltage side of the ignition is OK.

I can’t claim anything like Mr. C’s knowledge, but as a marginal motorist in my youth I have experience of the ways of many old motors.

Christopher Carnley · Posted: Thu Oct 18, 2018 4:47 pm Post subject:

First sentence, so very true, and for the HT leads.

Chris Card · Guest

I know nothing about Derby's and this is probably a silly question, but if the electrics seem OK, have you got petrol in all the right places?

Chris

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

Given that you have a new head on, have you checked compression?