Vac Advance from Carbi to Cap Problem

Rei,

You won't be getting a vacuum when the engine is idling - at least not one that activate the vacuum adv & retard. The vacuum adv/ret only works when you rev it really hard. Before that point in the rev band it's the mechanical adv/ret, located under the ignition distributor baseplate that does the job of advancing the ignition timing.

You could try GENTLY poking out the hole in the inlet manifold/carby with a piece of fine wire in case there's a blockage. It's a very simple system and there's not much in there that you can damage.

The final solution is to get a tiing light on it to check the amount of adv/ret. This is quite easily done by referring to a GOOD workshop manual and then checking it with a timing light. A mechanic would take about 15 to 30 minutes to do this.

Bilbo

the vac advance on the rb30 runs on a set of ball bearing that seize up.
if your basically mechanically minded its quite an easy job or a good mechanic should be able to do it in a short time.
also on the mechanical advance the little spring can break pull your cap of and see how much free play in the shaft with the rotor button on it there shouldnt be more than 5mm or so before the mechanical advance starts to work

Have you checked if the vacuum diaphragm is OK. Not holed?
Put screwdriver into distributor & push diaphragm rod to one side towards the vacuum line the put your damp finger over the line entry & remove the screwdriver.
Should be able to feel vacumm from stretched diaphragm on finger particularly when you remove it & watch to see if the diaphragm lever moves back.
Think it would be unusual for hole in carby to be blocked.

Rei,

I'd hazard a guess that the manual that you have is NOT a genuine Nissan manual. Some of the "Gregory's etc" manuals are inaccurate.

For a start I would find it highly unusual to find an engine that has 15 degrees of ignition advance when the engine is idling. 5 to 6 maybe but 15 is a bit over the top. Max advance is at max revs, and most engines don't go beyond 20 to 30 maximum advance when flat out.

Bilbo

It's been a while since I played with a carby.

But if I recall correctly, some carbys shutoff the vacuum advance at idle and only apply vacuum when the throttle opens. Do you have any driveability/economy problems?

Another happy customer from "SUPER MECH"................or I was, about 20 odd years ago. These days just changing a tail globe gives me the screaming s**ts. And don't mention actually cleaning the car,,,,,,,,,,,,,,,,,,,,

Bilbo