When it goes bad do you get hesitation on acceleration? I have hesitation on acceleration . i checked the carbs ,pulgs all look good .

The purpose of vacuum advance on the old dizzy is to prevent "acceleration stumble" (what you just described). Because the old round top SUs had no accelerator pump circuit, the distributor vacuum advance was crucial to smooth, stumble-free acceleration. The later flat-top SUs had separate accelerator circuit flaps to overcome this, but they had other problems of their own.

There should be no likely reason your carbs are responsible for this, unless you changed something.

Pop the dizzy cap and experiment with the breaker plate. See if it rotates back and forth easily, like the rotary dial on an old telephone. It should be able to spin a few degrees in one direction, then back. If not, take it apart and lube it. Also check (all) your vacuum hoses for leaks, but especially the one leading to the vacuum advance dashpot (diaphragm) on the side of the distributor body.

The system is simple; a spring holds the movable breaker plate in the 'advanced' position, and during operation manifold vacuum pulls it back into normal operating position against spring pressure. Picture it as an active 'tug of war' btwn the spring and vacuum, with vacuum usually winning. When you hit the throttle, the open carbs allow big air to rush into the manifold, dropping manifold vacuum. That allows the spring to "win the tug of war" momentarily. The breaker plate spins a few degrees, advancing the spark. As the engine speed increases, manifold vacuum rebuilds, pulling the plate back into the normal position again.

You just have to ensure the plate moves freely a few degrees back and forth, and the vacuum hose doesn't leak.

The weights are for high speed advance and shouldn't affect what you're describing.

Warning: If you disassemble the dizzy breaker plate, make sure you don't drop any tiny parts (especially tiny screws) down inside the distributor shaft. Having a small magnet on hand to handle them is a safety feature.

AND, while you're in there, always check your breaker points to ensure they are in good condition and maintain a proper gap.

Good luck ~
Frank

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1970 240Z

Thank you i changed the vacuum hoses and for now its driving really good... wow vacuum lines are important.

I loved the old Zs. They were simple systems which anyone could work on with a basic metric tool kit.

Glad you're functional again ~ good work!

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1970 240Z

If i had to change the vacuum advance do you know where i could get one ..cause no autopart in nyc could get them. i would like to buy one as a spare.

Ive known guys who drove around with spare distributors in their toolkit, just so they could swap them out in a hurry if something went wrong on a roadtrip. No time wasted on roadside troubleshooting to see what went wrong ~ just swap out the whole dizzy and be on your way in 10 minutes.

Several companies make replacement dizzys for the old S30 Z cars. Mallory makes a good one, which includes an external adjustment for the ignition advance. They cost around $400. If you can find an old 240Z in a junkyard, you can usually get the distributor for under $40. You could then spend another $200 and have it completely rehabbed, and have a drop-in spare ready in case anything goes wrong.

But the secret to having a healthy distributor is routine maintenance and cleanliness. Your old breaker-point vacuum-advance distributor is not hard to understand or work on. If you pay them the respect of opening them up once a month and cleaning them with a Qtip and pipecleaner, and lubricating the vacuum advance plates and replacing the points and condenser (capacitor) every 5,000 miles or so, your dizzy should last until the bearings wear out. The cap and rotor can be cleaned up and filed with an emory board to keep them running until they're just too worn to work. You get to know your Z better that way and to recogniZe the little idiosyncrasies it shows when the points need attention. After the 2nd or 3rd time you clean it, your distributor becomes like a woman you know well ~ when it sounds odd or acts differently, you know it needs attention.

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1970 240Z

Frank what's pipe cleaner also what lube you use.

Pipe cleaners are soft cotton "cleaning sticks" made to clean tobacco smoking pipes. They are flexible and twistable so they fit into small places and kids use them to make things out of in craft classes. I use them to clean tiny places on my Z and to clean firearms or clocks or anything a QTip won't fit into. Pipe cleaners are absorbent so they are very good at cleaning out moisture from delicate machinery. They are cheap, usually costing only $2 for a bundle of 70. You can buy them in any tobacco shop.

LubriPlate used to be an excellent lubricant for the Z distributor, but I haven't seen it in about 30 years. I have used white motorcycle grease (what they used for motorcycle chains, back before every motorcycle became belt-driven) and that worked pretty well too, if you used the light weight stuff instead of the thick stuff.

When you buy a new set of ignition breaker points, the box usually has a little balloon of lubricant in it. That is supposed to get smeared around the cam to keep the point cam follower from wearing out too quickly, but it also makes an excellent lubricant for the breaker plate.

There isn't much surface area bwtn the plates which need to be lubricated; only a few raised surfaces actually touch the other plate, and that's where you should lube it. Vaseline even works better than nothing, but it doesn't last as long as other lubricants. Just don't put too much on there ~ you're only trying to make the two plates slide against each other easily, and that doesn't take much lube.

http://en.wikipedia.org/wiki/Pipe_cleaner

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1970 240Z

I currently have no vacuum advance since in the process of installing the carbs I broke the vacuum advance port off the carb.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Some people claim better performance by re-routing the vacuum hose from the distributor dashpot to a designated nipple on the intake manifold, rather than onto the front SU. I've never tried it.
Either way, you'll want to cover that carburetor hole somehow.
Your Z won't be happy until you have a good working vacuum advance.

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1970 240Z

Actually super glued it shut. Ill try the intake but was told that wouldn't work. Ill see if I see any difference.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Frank Ive learned alote in the pass weeks about the Z cause of you thank you. this vacuum advance is important to the zcar .. So getting ready cause im leaviing tomorrow to NH just in case i have problem. I think ill have a smooth drive .

The value of belonging to this Club is having others to help you when you have questions or problems. These cars are fairly simple and easy to work on. It's easy to learn about them.

Your car is in such excellent condition I don't think you will have any problems at all. It's just a 4hr trip for you if traffic is light.
Take it easy and stop to rest along the way and let the car cool down a little. You will certainly meet people along the way who have questions and comments about your beautiful 240.
Have a safe trip and I'll zee you up there Monday.

You're about to have a wonderful experience at ZCon!!!

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1970 240Z

Thank you again this is my first time. i can't wait to learn what it is to have a Z. see you Monday and all week .

Related to the topic: anyone used vacuum advance with triple carburators? I have SK/OER carbs and they have vacuum advance port, wich im going to use. Will it be enough to use only 1 or should i take the vacuum from all of them?

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