Finding BTDC without timing cover marks

[David53]

Last week I attempted the "twist it and see" method of setting timing and unfortunately did not tippex the dizzie first. I could not get the engine to "pink" which was the idea of the exercise. She is now running quite badly so I need to reset the timing back to TDC and start again.

My car has no timing marks so my plan is to establish TDC by watching a chopstick placed in spark plug one hole and stopping when at the top of the stroke, then connect a bulb across the dizzie and twist body until light comes on.

This should give me correct timing at TDC. My question is, with no timing marks how can I establish what is 5 degrees BTDC? I assume rotate to the right, but how far?

[MarkyB]

Looking at the front of the engine you need to turn the bottom pulley anti clockwise about a quarter of an inch.
I'm assuming the spaces between the degree markers will be the same as on the later engines.

It might be worth going further anti clockwise then back to that point to take up and slack in the timing chain and backlash in the cam gear.

[RogerRust]

Sounds about right to me.

When you have found TDC make some sort of timing marks on the pulley then you will know where to start next time.

[RogerRust]

By the way you only need to move the distrubutor a tiny amount because it turns once every two revs of the engine so five degrees at the distritutor is ten at the flywheel.

[David53]

OK so prob best solution is

1: Find TDC
2: Mark Pully and cover with this mark
3: Turn pulley back about 1/4" (back further then closkwise to this point)
5: Adjust Distributor to open points at this position

Yes?

[bmcecosse]

Never turn back ! That's when all the 'slop' sets in! But really - just set it to give the nicest idle - that's all that matters. And if the vacuum unit isn't working - it's all a waste of time anyway!

[David53]

Yes I think you're right BMC. The vacuum advance unit does not seem to be working, when I suck on the pipe there is strong resistance but no movement, which would indicate it is jammed up. The timing is now set about right (althought advanced furtehr than it should be) but still have a lumpy idle, so it's distributor out for a clean & rebuild.

Does anyone know where I can source a replacement vacuum advance unit with screw on connectors? All the ones I've found seem to be push on types. Can't use these as carby is screw on as well.

[David53]

OK have pulled the dizzie out. It seems in quite good nick - spindle spins freely, everything is quite firm

However, if I suck as hard as I can on the end of the vacuum advance unit nothing turns. There is a strong resistance, and I can see the bar of the unit move against the backplate. If I try and move the backplate with my figers by pushing on the condensor it is very stiff and hard to move. I am presuming it should be very light? But it doesn't feel like it's jammed up it feels like the springs are too strong - the resistance is very strong. Is this normal, or should it be very eay to move?

Plan to strip it down tonight and check it over so any tips would be welcome

[bmcecosse]

No - it should turn very easily against the fixed baseplate - so it's just gunged up. If the vacuum unit 'bar' is moving - it may well be ok! I doubt you wou;ld get a new one with 'screw on' connector - unless you can find new-old-stock, so you would simply connect to the pipe from the carb with a short length of (non vacuum collapsible!) tubing. Once the vacuum assembly is working - things should go very much better! You will set the static advance for starting - as soon as the engine fires up it will create a vacuum - which then pulls the timing forward to give a nice idling setting. It also helps economy by pulling up the timing any time you are running with light throttle.

[dp]

You could take off the distributor cap, and stick on a plastic protractor with a bit of bluetac. Then just attach something as a pointer so you can measure small movement. I tend to do the same thing but on the crank wheel but that might be too awkward to get at.

[David53]

I have found a new screw on advance unit from ESM. I am concerned the backplate will be hard to free up - the felt pad between the plates is oil soaked and quite gunged

[bmcecosse]

Soak it in release oil. Well done finding a 'screw-on' vacuum advance.

[MarkyB]

Wear in the distributor is often in the bushes that the shaft runs in.
The easiest way to see the effect is with a timing light on a running engine.
If the timing mark seems to jump about rather than appear in the same place every time then it might explain why it was difficult to time the engine.
For best performance the spark needs to occur at exactly the right time not approximately or randomly.

[bmcecosse]

Aye - but that 'exact' right time is constantly changing - depending on throttle position, air temperature and engine revs. This is where the Megajolt systems make such a difference - I just wish I had the skills to build one ! Eliminates the dizzy from the point of view of generating the spark - it simply directs it to each plug in turn, but takes no part in the 'timing'.

[dp]

Aye - but that 'exact' right time is constantly changing - depending on throttle position, air temperature and engine revs. This is where the Megajolt systems make such a difference - I just wish I had the skills to build one ! Eliminates the dizzy from the point of view of generating the spark - it simply directs it to each plug in turn, but takes no part in the 'timing'.

Try one of the little Maplins kits first it's not that much harder and it's only a fiver or so if you break it. Actually, the Megajolt has better instructions than the Vellemans kits

[bmcecosse]

I doubt Maplins do a full 'mappable' ignition kit for a fiver!

[MarkyB]

Excessive wear in the distributor shaft introduces randomness into the timing.
Are you suggesting this is a good thing or just moving off at a tangent?

[dp]

I doubt Maplins do a full 'mappable' ignition kit for a fiver!

No, I meant a kit of a flashing christmas tree or a electronic dice. You could try one of those to get some practice in & build your confidence up.

Bear in mind the Megajolt needs a trigger wheel attached to the crank pulley and a Ford EDIS ignition module. I don't think it can run off the distributor rotation unfortunately.

[bmcecosse]

That's the whole point - it DOESN'T use the dizzy - except to 'distribute' the sparks. And - I have a fair bit of soldering/electronics experience - but no way could I cope with building a Megajolt from scratch.

[bmcecosse]

That's the whole point - it DOESN'T use the dizzy - except to 'distribute' the sparks. And - I have a fair bit of soldering/electronics experience - but no way could I cope with building a Megajolt from scratch - and have the slightest hope of it working.