Trying to Set the Timing on CU

[InventEd]

OK I have had a few issues of lack of power when trying to accelerate and then the van not starting. Changed the fuel line, filters and checked fuel pumping through OK. Then van would not start after 2 weeks of not running. Changing the rotor arm and the dizzy cap has got the van up and running. So I have put a strobe on to see how the timing is. The notch is not clear but there is a tiny mark on the back of the fan that appears to line up with 0deg on the scale at tick over. Two types of dizzy in the Haynes manual, one is 8deg before and the other 4-6deg after. Which is right for my dizzy? Link to a picture of my dizzy below if anyone can identify. It is a type that works with the idel stabalisation/coil amplifier;

https://goo.gl/photos/j86hB2XA5wNJRy4V7

Dizzy appears to have just one vacuum connection on the side. It has the rotor arm with the little spring weight rev limiter built in. Running a 32/36 weber carb. If I set to 4-6 deg ahead (which is what it appears in the book it should be set to) it really struggles to react on the accelerator. Put it 4-6 deg before and it reacts nice and quickly to accelerator. Any thoughts or guidance appreciated on

a) what timing should this dizzy be set to
b) how do I confirm I am looking at the right notch. It looks almost like someone has just nicked the paint with a knife rather then a clear notch so I could be looking at the wrong mark (its a new engine so they may have painted over the notch?)

[bigherb]

If you are only using a single vac distributor the timing needs to be set at 7.5 deg BTDC, 8 deg is close enough
There should be a notch on the rear of the V belt pulley it's not very big.


Setting the notch to the marks on the timing scale around the pulley.


The idling stabilizer plugs need to be removed and plugged together when checking the timing @ 850 +/- 50 rpm and the vac advance pipe needs to be disconnected.
Check the vac can is working and not leaking air past the diaphragm.
As the vac can or distributor has been replaced it may not have the correct ignition advance.
If you get the distributor part number will give us some idea.

[InventEd]

Ahh ha, that may explain why at 4deg ATDC I am getting all kinds of strange pops and bangs when I accelerate! I will have a go at setting it with the vac disconnected at 8deg BTDC tonight. I am hoping that 12 deg change in angle should have quite an effect!!

I could not get the nut off the dizzy clamp plate to take dizzy off for identification. I can't get a socket past the vac diaphragm and a spanner is hard to get in there. So I have not managed to read what it says on the side of the dizzy yet. Once I have moved to 8deg BTDC I may be able to get at it and find out exact type.

Video below of how I have been running it. You see how it comes to a quick stop at the end with a backfire when I blip the throttle!

https://goo.gl/photos/J2e94UppmJ8TrQc97

One last thing. How do I check the vac advance. Can I just suck through the pipe and see if I get movement or is there a more scientific method?

Many thanks for the help.

[InventEd]

Just set to 7.5deg BTDC and it ticks over and picks up much better. Gave a few revs and the degrees increased. Pulled the vac pipe off and the timing dropped back a bit. Tried revving with the vac removed and the centrifugal was also increasing the angle. So both vac and centrifugal appear to be working. The strange part is with the vacuum pipe on if I rev the van to 2000-3000 revs the angle comes back so far it goes past the end of the scale (40deg)! Should it be retarding the ignition that much.? Bentleys talks about 19 to 22 deg I think.

Could i have the wrong rotor arm to get this much advance? The one I have looks like this;

https://www.vwheritage.com/shop/0719052 ... m-cut-out/

[bigherb]

The strange part is with the vacuum pipe on if I rev the van to 2000-3000 revs the angle comes back so far it goes past the end of the scale (40deg)! Should it be retarding the ignition that much.?

Hopefully you mean advancing the ignition.
It will do with the vac pipe connected as there is no load on the engine. With the vac pipe disconnected the advance should 28-32deg BTDC @ over 3400 rpm.

The rotor arm has no effect on the timing.

[InventEd]

Yes I mean advancing! Drove it last night and it ran really well, so I think that has sorted it! I will double check advance with the vac off and see what happens.

Many thanks for the help!