Electronic Ignition Timing Question

[DSG85]

First post here. I became a Land Rover owner for the first time five days ago.

When I got my Series IIA Landie, it ran pretty well but was rough between idle and about 2000 rpm, particularly under load. It also ran better with the choke pulled out slightly.

First, I cleaned the carb. The carb wasn't very dirty. It's a new Zenith carb that is less than 2 years old. I didn't think that the carb was really the issue, but it didn't require any parts and I figured it couldn't hurt. That didn't change the issue much, if any.

After further research and diagnosis, I determined that the vacuum advance diaphragm was busted. As I was planning on eventually switching to electronic ignition anyway, I ordered a replacement electronic distributor and a new coil that should arrive today.

My question is, how do you properly set the ignition timing if the marks on the flywheel only go to 6° before TDC? I haven't seen the specific instructions for my new distributor, but instructions for electronic conversions I have read say to set timing at something like 30° BTDC at 3,500 RPM (don't pick at these numbers, they are not meant to be specifically correct for a 2.25 engine, they are just for describing my anticipated problem). How have people who have gone electronic set the timing to a spec like this which would need a mark well before 6° BTDC? Did you just start with the distributor set as it was out of the box and tune it by ear or what?

I was thinking about counting ring gear teeth and making my own mark based on that. I saw on another forum that said the 2.25 petrol engines have 98 tooth ring gears, can anyone verify this? I couldn't find another reference for the the number of fly wheel teeth.

Thanks in advance!

[lumpydog]

Well welcome aboard! Post some pictures if you can - would love to see your truck.

You should get a timing light - Amazon sells them - I bought this one.

The timing light clips to your car battery for power and to the spark plug on cylinder 1 to pick up the spark timing. It strobes onto the timing wheel and you can set the timing light to the advance or retard that you want to achieve on the timing light settings. Then set the spark/ignition so the timing mark on you engine is TDC (the timing light moves the strobe speed/timing so what appears as TDC on your engine sets the actual timing to your timing light's selected advance or retard setting. For example, if you wanted to set your engine to 6 degrees before top dead center, you would set the timing light to 6 degrees advance. It would then adjust the strobe light so, with the timing mark in your engine set to TDC, it's actually 6 degrees BTDC. Then, set the timing light back to zero and you can then see the timing mark advanced 6 degrees of the TDC pointer on your engine.

Most here will tell you to set timing by feel. I do that, using the timing light as a guide/check. Search this forum and you will find plenty of posts about setting timing by feel.

[o2batsea]

Timing remains the same. It is determined by the CAM and not by the DISTRIBUTOR.
In addition, electronic ignition will probably not do anything to improve a lumpy engine if the issue is fuel related. I would hazard a guess that your carb is probably gunked up. With the advent of ethanol laced fuels, these old carbs become very unhappy when the ethanol does crazy stuff to things like the rubber fuel lines and the internals. Particularly the needle valve which may not have the viton seal.
I'd advise a complete teardown of the carb, or at least blow the jets out with compressed air and have a cleanout of the bowl.

[mearstrae]

I believe the technical term would be "Ignition Timing". This timing should be set with the vacuum advance disconnected and plugged on the intake manifold side. Try using a vacuum gauge, plugged in to a manifold vacuum source, (as opposed to the spark port, where the distributor is plugged in) to set ignition timing to the highest steady reading (about 20" Hg). This tool will also point out other troubles that may be present (vacuum leaks, intake valve leaks, and other things). Unless you have a dragster, 30 degrees initial advance would be a bit too much, there's a big difference in "initial" timing and "Total" advance timing. I'm not sure what the Green Bible says the initial timing should be, surely not more than six to ten degrees of advance.

'99 Disco II
'95 R.R.c. Lwb (gone...)
'76 Series III Hybrid 109
'70 Rover 3500S

[DSG85]

So here's my update and some clarification:

When I said timing, I meant ignition timing not valve timing. I thought that was fairly obvious
When I said initially set to "something like 30° BTDC at 3,500 RPM." I did not mean static timing, that would be at zero RPM. I meant that with the new distributor installed in approximately the same orientation as the original distributor that is what I would see with a timing light at 3,500 RPM.

What I realized after I posted this is that the timing light I ordered can be set to an angle of advance, like lumpydog suggested, and the only mark I need is TDC.

Now for the update: Last night, I installed the new electronic distributor and set the timing to approximately the same advance settings as the original Lucas 25D4. It runs a little better than it did, but it still has some hesitation between idle and higher revs. The problem is more noticeable the faster the throttle is advanced. This makes me think it is the accelerator pump in the carb. Like I noted in my previous post, I just cleaned the carb and nothing looked too bad when I opened it up. I did clean the accelerator pump parts and orifices.

Does anyone have a specific suggestion on what to do to the carb? Should I just do another strip and clean? Anything specific to look for? I read that it could maybe be the accelerator pump piston sticking. Does that sound right to anyone? Any suggestions on how to fix that? New piston or what?

Thanks

[o2batsea]

Answered already. But again: take it apart and blow out the jet orifices with compressed air (not canned air, REAL compressed air from a blow gun attached to a COMPRESSOR) pay particular attention to the emulsion tube and the gunk in the bottom of the fuel bowl.
Usually hesitation like you describe can be attributed to fuel starvation occurring as the carb transitions from the idle jets to the main jet. The accelerator pump comes into play by adding extra fuel to smooth out that transition.

All that said, rebuilding a carb is only as good as the effort put into it. You really need an ultrasonic cleaner and you really should take out the little slugs they use to plug up the end of the tubes. Nobody has time for that craziness of course. It's usually more cost/time effective to buy a new one.