Early Euro M20 Timing Adjustment

[SaturnBlau]

Hi,

I’ve just changed the timing belt, accessory belts and water pump etc. on my early 1985 euro M20B20 engine. This is the one with the gear driver distributor located behind the alternator.

Put everything back together and the engine turned over fine (no bent valves) and started fine but noticed it was idling around 3-400 rpms and unevenly. It’s also very gutless between 1-2k rpm and backfires when letting off the throttle from 2k.

I’m figuring that when I changed the belt, I also managed to alter the timing of the intermediate shaft running the dizzy and now the timing is retarded (engine runs sweet when revving).

My question is if anyone knows how to adjust the timing and advance it a little on these older engines. I have read that taking out the dizzy and rotating will do the trick but can this be done with the engine running and will it need a timing light?

Basically need a DIY guide

Thanks in advance

[Brianmoooore]

With the crank timing mark lined up to TDC, and the valves of cylinder 1 closed, there should be a notch on the distributor body that lines up with the rotor arm, IIRC.
If the engine runs, you can't be far out, so rotating the distributor should be enough to correct it.
According to Autodata, your car should be timed at about 20 degrees BTDC at 5000RPM, with the vacuum advance pipe disconnected. This is best achieved with a timing light, but experience and/or trial and error will give reasonable results.
Turning the distributor body the opposite way to that which the rotor turns advances the ignition.

[SaturnBlau]

With the crank timing mark lined up to TDC, and the valves of cylinder 1 closed, there should be a notch on the distributor body that lines up with the rotor arm, IIRC.
If the engine runs, you can't be far out, so rotating the distributor should be enough to correct it.
According to Autodata, your car should be timed at about 20 degrees BTDC at 5000RPM, with the vacuum advance pipe disconnected. This is best achieved with a timing light, but experience and/or trial and error will give reasonable results.
Turning the distributor body the opposite way to that which the rotor turns advances the ignition.

Thanks for this Brian, ended up getting there with good old trial and error. Twisted the dizzy a little at a time and ended up going as far as it would go anti-clockwise. Intermediate shaft must be a tooth or two out.

Runs great now anyway, revs all the way to redline which it didn’t do when I first got it (seemed to hit a limiter around 4.8k rpm).

Will keep an ear out for any pinging or backfiring and will check the condition of the plugs after a bit of running but I think it should be good for now.

[TheWolfman]

Just to chime in, the timing mark on the distributor itself should actually be alligned to the 'Z' timing mark on crank pulley, not the '0' mark. The 'Z' stands for 'zeit' which is German for 'time' and is marked on the pulley at the appropriate 22 degrees of advance and so this is what should be used as reference for correct time alignment at 5000RPM.

Thought I'd point this out as I see a lot of people referencing the '0' TDC mark and this will actually the retard the timing by 22 degrees, and especially if timed to this at idle will send the timing way out.Hopefully this is helpful.