One thing that did arrive in the post this week was a pair of lockwire pliers, which will undoubtedly be useful for lots of things but their first outing is to replace the rubber O-rings used to lock the advance on the distributor. I never liked the rubber rings – they seemed generic, stretchy and not the right size. That’s not based on science and it’s not knocking Aldon, it’s just a gut feeling.
With the dizzy out of the car, we want to get to the advance plate that’s way down at the bottom of the carb body. The (relatively) easiest way to do this is to completely strip the dizzy, using a few vague references found via Google to guide you, so for posterity I thought I’d add something here. First you take out all the Ignitor bits, or points if you’ve still got them, which then gives you access to the vacuum advance plate. To get this out, you need to tap where the arrow is with a small drift to rotate the plate clockwise by about a centimetre.
This then reveals the dynamic advance plate, which would usually have two springs connecting the posts to control the rate at which the advance weights fly out and thus twist the shaft round, but instead here you can see the rubber O-rings.
Getting them in there was hard enough, so to replace them with lockwire I want to pull the shaft out out of the body. To do that, you get your small drift and gently knock out the roll pin that locks the ring gear onto the shaft.
Then use a gear puller to pull the gear off the shaft – destroying a perfectly good £2 coin in the process
With the ring gear off, the shaft slides out and you’ve got yourself a workbench full of bits.
So we can all see what I’m talking about with advance weights flying out and turning the shaft, here they are closed on the left as they would be at idle and at max swing on the right, limited by the stops. There’s really only a small amount of movement between fully closed and fully open and if you stay with a mechanical distributor, that’s what you’re playing with different springs for to try to control the rate of movement across the rev range. That’s in combination with the shape of the lobes on the weights and the position of the stops, of course.
The lockwire pliers made it terribly simple to lock the advance off, with the added benefit that it looks rather swish too The advance weights are free to flap around, but they can’t turn the shaft.
Reassembly was straight-forward, apart from my gear puller not being big enough to use to pull the ring gear back onto the shaft. A 14mm socket and a rubber mallet were plenty fine instead – just be very careful to line the ring gear up with the hole for the pin, as there’s no way you’d be able to twist it round later if it was even slightly out, so you’d have to pull it back off and start again. For once though, luck was on my side
And that’s where the luck ended. It was only when I went to put the dizzy back on the engine that I realised in my eagerness to get on with the job, I’d not made a note of where anything had been positioned, so I had no idea where to line it all up so that the timing would be unaffected (or even close to what I wanted). This was confirmed as I spent the next hour trying to get the thing started and getting nowhere nearer than a splutter and a few backfires.
Bollocks Time to push it into the garage and close the doors …
me: I’ll give it a go
- Mechanical advance on the dizzy is locked as that’s under the control of the Aldon Amethyst.
- Vacuum advance on the dizzy is not plumbed in, so will always be at atmospheric and thus (in theory) not move
- Vacuum advance could be applied by the Amethyst at a later date IF I can get a stable reading across the four manifold ports
If it’s better to completely remove the vac advance gubbins from the dizzy and replace it with an arm that locks the vac advance plate in place and screws to the dizzy body, I guess I can do that too. Advice always appreciated
me: I had the crank at the TDC mark, took the plug out and felt the top of number 1 piston, then pushed the distributor home with the centre of the rotor aligned with the mark on the dizzy body and everything I’ve read on the interwebs said this should at least give me something … whereas I got nothing I turned the dizzy this way and that and got nothing more than the occasional pop or bang for my trouble, then called it a night before I got too pissed off.
Then overnight I had a thought. Given that I locked off the advance the way that Aldon suggested, it’s locked at max advance. Remembering that I measured the centrifugal advance curve of the dizzy a while back, I looked up my notes and it applies 24 degrees at full whack. So it now occurs to me that when I thought I was setting the static timing to 0 degrees, I was actually setting it to 24 degrees BEFORE TDC which might explain why it was having none of it when I try to start it.
Does this theory make sense ? If so, is my best option to pull the dizzy out again and lock it at MINIMUM so that it’s equivalent to no centrifugal advance, at which point the standard Pinto static timing methodology ought to come back into play ? It’s annoying but if it wants doing then so be it – looking for a sanity check, but equally happy to have my whole theory ridiculed…
Graham: but unless you also looked at the cam or felt for compression on no 1, you dont know if 1 or 4 was on its firing stroke, 24 degrees would be a lot of advance to start, but i would still expect it to do so especially as you said you tried twisting the dizzy,
the reason aldon would get you to lock the dizzy at max advance isnt to do with timing, but rotor arm position relative to the contacts in the dizzy cap, with mappable systems typically running a lot more advance in places you can be in the position where the spark timing is so advanced in-relation to the now fixed rotor arm the spark ends up going to the wrong cylinder, cross firing as its known as.
id say most likely your just timed up 180 degrees out
me: Graham nails it once again… reminding me that I need to step back and think things through a bit more. My engine is vanilla enough that it’s still got the standard cam pulley, so it’s got that convenient little pointer that I completely forgot about.
Got back tonight, turned the crank round until it hit TDC, saw the cam pointer was by the marker dot… and the rotor arm on the dizzy is off pointing somewhere near no. 4 It’s ridiculous how much of what little knowledge I had that I’ve forgotten over the last few years, where all I’ve needed to do is turn the key in the Focus. Don’t think the neighbours would appreciate me mucking about and trying to start it at this time of night though…
Hoiked up the dizzy, realigned the rotor to the there or thereabouts mark, turned the engine over a couple of turns and the distributor only wanted a little nudge further round to give me a stable idle. Warmed it up, got the strobe on it and set it to 10 degrees. Lesson re-learned and job jobbed