Ignition Timing

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Graham
Posts: 5
Joined: Tue Feb 05, 2019 3:03 pm

Ignition Timing

Post by Graham » Sat May 16, 2020 12:29 pm

Hi everyone

I want to check my ignition timing on my P3 75 using a strobe light. I have found TDC on the flywheel & it's my understanding I set to the FA mark. Assuming this is correct my problem is I can't see a marker on the casing! Can anyone help please. There should be a pic attached.

Also the car has fitted a basic electronic ignition which seems to work very well but should this alter the timing position?

Advice much appreciated.

Graham
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TonyG
Posts: 112
Joined: Mon Sep 07, 2015 4:38 pm

Re: Ignition Timing

Post by TonyG » Sun May 17, 2020 9:49 am

Hi Graham,

I'm no expert on your car but, unless you have details of the dynamic timing settings, you cannot set your timing with a strobe.

The FA mark is used on my pre war cars to set static timing, I.e when points just opening. Suggest you check procedure for your model in workshop manual, which should also detail the crankcase mark you use. My cars have a pointer but yours clearly does not.

When using a strobe the vacuum advance pipe, if so equipped, is removed and the engine set at 1000 revs or fast idle. The weights in the distributor will advance the ignition slightly and the timing is adjusted to a pre determined 'dynamic' mark. If you adjust to the FA you will end up with a greatly retarded setting.

Hope this helps a bit.

Tony
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

Ray
Posts: 13
Joined: Sat Feb 22, 2020 1:30 pm

Re: Ignition Timing

Post by Ray » Sat May 23, 2020 2:32 pm

Hi Graham, were you able to find out where the 'Timing Mark' is on the case ?
Also, can you tell me which piston was on the compression stroke when you took that photo ?
The reason I ask is that I have two P3 75's and they are each timed differently. One is at the TDC mark when cylinder 1 piston is on the compression stroke and the other is at the TDC mark when cylinder 6 piston is on the compression stroke.
The RSR Workshop Manual states that cylinder 1 is at the front of the engine which I have taken to mean nearest the radiator.
Both cars run well like this but I don't know how that can be or which one is how it was originally designed to be.
All comments will be much appreciated.
Regards, Ray Lilly

TonyG
Posts: 112
Joined: Mon Sep 07, 2015 4:38 pm

Re: Ignition Timing

Post by TonyG » Sun May 24, 2020 9:25 am

Ray,

Clearly, one of your cars is incorrect and I suspect it is the one you are timing on 6. Im not familiar with the 6 cylinder engine but I suspect that piston 6 firing stroke is 180* out of phase with piston 1. No reason why setting it up on this one shouldn’t work fine, given that each cylinder requires the same accuracy of timing. However, the reason that 6 aligns with the timing marks and 1 doesn’t suggests that the flywheel may have been fitted incorrectly at some point in the past. I seem to recall from the reassembly of my 12 engine that there are ‘0’ marks on the crank and flywheel to ensure this doesn’t happen. I’m sure there was something about retaining the balance as well although, with subsequent wear of the starter ring upsetting this, I cannot believe it matters much on anything but a highly tuned engine.

Tony.
Tony Gilbert

P1 12 Tourer
P2 12 6 Light Saloon
Discovery 3
Discovery Sport

HAD501
Posts: 10
Joined: Thu Apr 23, 2020 10:48 am

Re: Ignition Timing

Post by HAD501 » Sun May 24, 2020 2:08 pm

Ray - I think the answer is in the camshaft timing. Making the bold assumption that P3 is the same as P2 and P4, the procedure is - set the crankshaft to EP, set the camshaft so that exhaust valve 1 is fully open and fit the timing chain. So it depends which cylinder you take as no. 1.

Returning to Graham's question, the timing pointer on P2 engines is a cone-pointed screw which protrudes into the flywheel housing from the cylinder block side - and isn't all that obvious. It looks like your P3 might be the same. The photo the inside view on a loose housing.

Hopes this helps, Dave
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Ray
Posts: 13
Joined: Sat Feb 22, 2020 1:30 pm

Re: Ignition Timing

Post by Ray » Mon May 25, 2020 11:51 pm

Thank you to everyone,
The comments and photo help a lot.
Regards,Ray

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