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Discussion Starter · #1 ·
Or, should the subject be how does not having vac adv. hurt me. The cap on the emissions cansister is broken, so there is no vacuum going to the distributor. So is this bad??? Does it hurt performace??? Should I not worry too much about it??? Thanks.
 

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Discussion Starter · #2 ·
> Or, should the subject be how does not
> having vac adv. hurt me. The cap on the
> emissions cansister is broken, so there is
> no vacuum going to the distributor. So is
> this bad??? Does it hurt performace???
> Should I not worry too much about it???
> Thanks.

Yes you should worry about it, and it does hurt performance. Without vacuum advance, your car will lack the crisp, or quick responce off idle.
Otherwords, your cars throttle responce will be sluggish if your distributor is not vacuum advanced.
But simply hooking it up to a vacuum source does not gurauntee advance in actual timing. Simplist way to check for vacuum advance is with a timing light. Time the engine with and without vacuum to disdributor. If you have sufficient vacuum, there should be at least 4-5 degrees advance.
 

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Discussion Starter · #3 ·
Re: Vacuum is very good for you

Take your distributor cap off, and hook a vacuum line up to the advance unit. Put some suction on it with a vacuum pump or just suck on it...the breaker plate should move. Many times, if the VA has been disconnected for a while the breaker plate rusts or the Vacuum chamber's diaphram leaks, I'm not sure how your vacuum is routed but the advance vacuum usually comes from a carb port or a ported vacuum switch. It will make a big difference when you get it working, if you need a VA unit, bend over -they are hard to find and expensive. try to find one at a Junk yard that works.
 

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Both suggestions above are excellent. Only thing I might add regards the year of your car. If it's a fuel injected car ('75 or later), vacuum plays a huge role in how good the car runs, accelerates, etc. because any air leak anywhere in the engine will throw off the air metering. A trick I saw on a Zcar tuneup video is to get an injected engine running at normal temperature, then take off the oil filler cap. If the engine starts missing and running bad, it means the vacuum system (with the cap on and tight) is okay. If there's no noticeable change in the way the engine runs, there's a leak somewhere in the vacuum system.
 

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Discussion Starter · #5 ·
Re: Vacuum is very good for you

Vacuum advance is extremely important for Z cars, but what should be correct is a matter of trial and error. Nissan did not set the advance correctly on the 280z distributors, but at least the advance is adjustable by chipping off the epoxy on the back of the advance mechanism. Oh, BTW, the vacuum advance does not really advance ignition timing, it pulls back on the breaker plate to retard ignition timing so there won't be any detonation upon full acceleration. If there is detonation, you lose power and economy. Now if your vac. advance is bad, don't buy just the part from the dealer, buy a whole distributor from your local parts guy for around $100.
 
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