Aircooled VW South Africa

Haans wrote: ↑Fri Apr 29, 2022 2:42 pm ........ we must NOT do is to hook up the vacuum advance ????? according to him 36 DCD"s don"t like a Vac advance.
......regards Haans

Totally agree , the vacuum is not a constant draw from the carb, unless the pipe is broken or off.

The vacuum stays in a closed system so will not draw off the carb.

And as long as the jet pump is set correct, she will perform like any other carb.

OMO

Herman

So the thing staring with a Z started & rev's up nicely. Still need to buton up the airfilter and tweaking the idling.require some 5mm bolts.
However,....this Z thing has centrifical advance as well as the vacuum advance ,....so help me understand this lot.
Vac adv for intial advance then sentrifical takes over as the revs increase.
Haans

As far as I know, the centrifugal advance is just speed related.

So as the engine revs go up the timing gets retarded (should read advance) so as to take-up the delay in explosion.

The vacuum only comes into effect on acceleration.

So when you put your foot down, you open the choke and you loose all the vacuum,

retarding the timing for better pull, and as the choke closes she builds up vacuum again and advances the timing again.

OMO

Herman

centrifugal advance is rpm dependent. As you rev up, you need the spark to happen earlier, thus it advances timing (Herman said it retards it).
Vacuum advance is load dependent. Less air charge in the cylinders (low load), burns slower, thus you need the spark to happen earlier to get improved fuel economy. But when on full load, the air charge burns faster, so you want the vacuum advance to no-longer advance.
For a slight fuel penalty, you can block off the vacuum advance and run purely on centrifugal.

Some more modern cars also had vacuum retard. This was used for supercharged engines (more dense charge burns even faster), or for cars that had the centrifugal advance setup past the point of where it would detonate if the car went into full load - so they took away advance (retard) to get it back to where it wont detonate.

Tony Z wrote: ↑Wed May 11, 2022 7:05 pm centrifugal advance is rpm dependent. As you rev up, you need the spark to happen earlier, thus it advances timing (Herman said it retards it).
....

You totally right Tony, How can you have a "centrifugal advance" retard the timing...

Sorry guys slip of the brain...

Yes its advance as can be deduced from my explanation.

Herman

Don't want to talk about this $&&$$&@ f-word thing anymore ... now it's got a misfire in the mid rev range
Will check valve clearences and if still there do compression check,....
Can't tell which cylinder yet ....too gatvol
Haans

Ok,.......after a whole range of fights between me & myself and I,....and with a whole lot of trial and errors,.....we got a new roto and distb cap from Windsor country,.....it is now running like a sewing machine !!!!!
Till next time,..................me thinks not
Haans

And........we are back to square one ??
Lasted for two days
Jury out on what next ......plug wires ???,....brand new ???

Haans

NGK plugs? Exchange them for Champion L87YC plugs.

I had a brand new set of spark plug leads which ended up back in the box or bin…can’t remember which….

Went to Midas and bought a set of Bougi’s

Bougi's are the best.

I also keep my old sets when I know they are still working well. It helps with fault finding and replacing bad wires if you find them.

Well,...............
......
....."it" is back from "diagnostics" and seem to be running fine,.....time will tell.

Up to now we've had "limited" feedback....could be that the feedback is g'na be on a " need to know" basis.......??

Haans

With today's business practices, it could double the bill if you need that kind of information.....

Cheaper to not ask....

But good news its running again, now we need to see for how long ....

Herman