[dmorris1200]

No! My way is right...

No! My way is right....

No! My way is right.....

No! My way is right.......

Blah blah, blah blah...........................too funny.

[underdog305]

Gotcha, by the end of this weekend i'll be a pro.. The new carb is on the way and the article from gofastforless.com completely answered everything.

[red65mustang]

I suspect the "go fast" article is (excellent) for a Ford, it parallels what I wrote, he doesn't say.

As 454c10 wrote:

The key thing is the Chevy and Ford spring/diaphram arrangements are opposite.... one is diaphram/spring the other is spring/diaphram.

Based on that, Fords like manifold, Chevy's like ported.

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Thanks again 454c10, been wondering for many years why a second 0 at idle port.

[dmorris1200]

You guys just keep reading all your DIY books and Internet blogs and you'll figure it out eventually...yeah right.

Also as already mentioned this has been discussed to death. Ford used ported vacuum for years on their carbed engines. I have been using ported for over twenty years in almost every engine I've built (mostly Fords), with few exceptions. In the seventies Ford actually used a dual-diaphragm vacuum canister that had two vacuum lines going to it. One connected to manifold vacuum but retarded the timing at idle to lower emissions, the second one was connected to ported vacuum and pulled the diaphragm in the opposite direction to advance the timing as soon as the throttle was depressed.

The best thing in that gofastforless link was this line "THEY ARE THE SAME THING! Except ported is shut off at idle." This has also been repeated here in older threads too many times. Depending on how much initial timing, engine set-up, centrifugal advance, etc. these things can all play a role in what will work best for any given engine. Oh, but then again, this has also been hashed through a million times over the last couple of years here at hotrodders.

[red65mustang]

thanks for confirming what I suspected about Ford "how the hell can we burn unleaded 87 octane" dual diaphram advance units

nah, we're gona beat it to death again.....wana see if 454c10 is right....suggest you delete the link

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underdog, your motor is fairly close to my street car(600cfm/214-214/9.0/10 and 36 timing),.... once you get the Demon on it,.... do try it both ways....my car sucks on ported, yours should work better than manifold

let me know

[underdog305]

Hey Red,
Summit has a sale on Speed Demon 575's now. I just got $20 back on mine. I'll definately keep ya posted on the carb/timing crisis. Aparently this issue has gone around the track a few times, but I have to say I learned a lot. Thank's guy's.

[Offy Dave]

I think one thing that may make this more clear is to think of the vacuum device as a retarder, not an advancer. It advances during idle when vacuum is high, but when you "nail it", it retards back to the initial timing to get the engine going. It retards because there is a big carburetor-sized hole in the manifold! And with all that fuel and low rpm, you need to retard the ignition, not advance it! As the rpm increases, the mechanical advance comes in until full mechanical advance rpm is reached. when you let off to cruse, the vacuum advance comes in again, on top of the mechanical. You know, in the good ol' days, a vacuum meter was an engine tuners tool of choice. hook up a vacuum gage to your manifold and drive around-see what happens at idle, wide open, and crusing, and you will see what that vacuum advance on the distributor sees!

[dmorris1200]

I would absolutely not think of the vacuum advance as a "retarder" instead of an advancer. If you forget to hook it up will it leave your timing advanced or retarded? If the vacuum line breaks will your timing be fully advanced all the time or retarded? The job of the vacuum advance is to do exactly what it is called... advance the ignition timing. How much additional advance it provides depends on how it is set. Also the statement "It advances during idle when vacuum is high" is false if it connected to ported vacuum as many are. This has been gone over sooo many times. A simple search with the boards search engine entering 'vacuum advance' brings up a ton of threads. This is just one fairly recent but I have probably reposted on this topic dozens of times, not to mention all our other members as well.

Ignition timing advance question.

There are sooo many different ways of setting up your ignition depending on how skilled/educated you are, how your engine is built, etc. No one way will make everyone happy.

[Offy Dave]

All I was saying , Dmorris, was that a simple vacuum unit, hooked straight to the manifold, (were talkin' old chevy here, ok) can only advance the ignition when there is vacuum. the "job" of a vacuum advance is to advance under high vacuum conditions, like at idle. but also to retard the ignition at low vacuum conditions, like low rpm-full throttle. when you are driving the car, the only way you can make the vacuum advance "advance" is if you took your foot OFF the throttle! like I said before, just drive a car with a vacuum gage and see for yourself.

I don't want to rub anyone the wrong way, it just seems like this is a mis-understood area.

[70bird]

"a simple vacuum unit, hooked straight to the manifold, (were talkin' old chevy here, ok) can only advance the ignition when there is vacuum. the "job" of a vacuum advance is to advance under high vacuum conditions, like at idle. but also to retard the ignition at low vacuum conditions, like low rpm-full throttle."

The way I understand it, from what I've read here, is that the vacuum advance canister does not retard the timing during low vacuum conditions but rather quits advancing it. I don't think it will retard it past your initial timing.
Just my $0.02.

[dmorris1200]

Originally posted by 70bird
the vacuum advance canister does not retard the timing during low vacuum conditions but rather quits advancing it.

Very well put 70bird. Dave I'm not looking for a fight over a play on words. But as 70 stated it is not a retarder because when energized it advances the timing. When you step on the gas the engine loses vacuum de-energizing the vacuum can causing it to stop advancing the timing. Either way it's job is to advance the timing either under light load conditions or under light load and at idle depending on how you hook it up. No matter how it is hooked up when energized it will advance your timing.

[Offy Dave]

yeah, guys. I give up! I read your post, dmorris, and you hit the nail on the head with that explanation. I guess what I call "retard" you all are calling "less advance".
this all came about when I was deciding on a distributor for my chevy 348 "w" motor. I don't have a stock distributor. mallory makes one....but with no vacuum advance. most people said I don't need it, but this is a mild street motor, and after some research, I think it will run better with the vacuum advance. turns out msd makes one with vacuum advance and it drops right in.
I came here to learn, and somtimes I forget that!

thanks, guys.

[dmorris1200]

Like I said Dave, a play on words. Actually I would say it was 70bird that hit the nail with that great line he wrote. Simple and to the point. Doing this for over twenty years professionally I am just a stickler for proper wording of things. Ex. : I hate it when guys say 'voltage is flowing' when I know that technically it is 'current' that is flowing and that voltage is just a measurement of the 'force' of the flow. You can have voltage without current flow but you cannot have current flow without some amount of voltage. Word play Dave, that's all.

[red65mustang]

dmorris,

about your last post in this thread

wrong!
Volts=electrons
Current=force=amps

It is how many electrons are flowing= how many volts are flowing.

The current is the force demanded by the load at a given amount of volts

But there is new (quantum physics) proof that an electron is both a physical entity and a wave at the same time but not a force.

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underdog, any answer yet, if 454c10 was right, spring/diaphram or diaphram spring for ported/manifold?

[dmorris1200]

What the heck are you taliking about ??? Volts don't flow, current flows. Ask any electrical engineer. Could you at least make sense when you post.

Volts=electrons
Current=force=amps

That is so wrong it is not even funny.

Volts= measurement of force
amps=measurment of current
current= movement of electrons
ohms= measurement of the resistence of that movement.

My statement is 100% correct. You can have Voltage in a circuit without any current flow or amperage, but you cannot have current flow without any voltage or pushing force.