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Author
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Topic: Ported vacuum vs constant vacuum question
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wilit
Mustang Messiah
Member # 3367
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posted
 
 
Rather than hijack norcalfiddy's thread, I figure I'd start my own. Here's my question:
quote:
Originally posted by wilit:
Not to thread hijack, but what is the vac advance supposed to be hooked to, constant or ported? I tried constant on my '68 and it ran like crap. I've read it should be on constant, but smog rules made it more efficient on ported. Not sure if that's true, but just what I've read.
And turbo50's responses
quote:
Originally posted by turbo50:
It depends on your preference and your engine combination.
Remember "VACUUM" advance is not going to work under full throttle in a MANIFOLD activated source scenario because, well there should be NO vacuum. If there is, your carb is too small.
Anyway, manifold source will have constant vacuum on it and ported wont.
What manifold vacuum source allows is at part throttle (light engine vacuum) and idle it allows more timing without being RPM based (springs and weights).
This allows the burn to be leaner at idle, which cleans it up and makes it idle better (closer to stoich). It also allows part throttle timing to advance (with no or light load). At full throttle or heavy throttle the advance goes away and you return to your initial timing setting and your weights,springs the MECHANICAL parts of your dizzy come into play.
The reason your car ran like shit with it setup is because you didnt spend enough time or werent fully educated with its function, IMHO.
It allows you to get better fuel economy. Lets your car idle without your eyes watering and allows for snappier throttle response when transitioning from part to full throttle.
Scenario:
Your engine likes to idle best at say 22 degrees of initial timing, you have NO vacuum advance (manifold) hooked up. So then you have to set your initial timing to 22 degrees to make the engine idle best with best air fuel ratio. Well, during hot starts this is less than ideal if its your INITIAL timing. Also, your motor may only like a total of 28 degrees of TOTAL timing...well only 6 degrees of advnace from 0 to say 3000 rpm? Not gonna happen unless you use heavy heavy heavy springs and then your carb will NOT responed well. So you set your initial to around 10 degrees with a total of 28 degrees all fully advanced at 3000 rpm for a timing spread of 18 degrees over 0-3000 rpm. Great. Carb will like that too! Well at part throttle that timing base is LOCKED in because it is mechanical. Same as at idle. Well you have to get an understanding of burns in the cylinder at idle and part throttle. They are WAY different than when under full throttle or a load. But they CANT change because you have set your spread in STONE with weights and springs, bushings etc in your dizzy. So it takes time after time to get it to run perfect and even then it suffers idle and MPG.
Now that same scenario but with VACUUM advance will allow this:
Set timing to 10 degrees base with vacuum advance OFF, unplugged. Set TOTAL timing to be 28 degrees (using, dyno, trap speed or wideband to see your specific engine combinations best performance). This STILL allows 18 degree timing spread from 0-3000 rpm when at FULL throttle. BUT you then hook up your vacuum and walla 22 degrees of INITIAL and it idles WAY better. Yet when cranking, especially hot there is negligable vacuum so your engine fires at 10 degrees base, then immediately sees 22 degrees base (the vacuum advance amount will vary depending on, vacuum canister, engine camshaft design,altitude and you can even buy adj vacuum canisters, using plus 12 as my example, put timing light on to verify) and your engine idles better. Gets better burn at light throttle (going down freeway) and burns more efficient causing better burn and using less fuel.
Ported, well there is several write up and debates but basically ported was a smog effort and is not present at idle, typically used in smog era vehicles that ran well and had egr and junk carbs that idles well and clean at very very very low initial timing settings and had dizzys that didnt see full advance, which with cam and compression in the toilet could be like 44 degrees and not at full advance until 4,100rpm....
PLUS then even had timing chain and gear sets from the factory (ford Modifieds as an example) that were designed with advance or retard in them.
I can go on and on
quote:
Originally posted by turbo50:
Think of it like this:
Its a prehistoric way, lol, of doing what the EEC functions do, on the spark side only.
i.e. you pull your spout to set timing.....set to say 14 degrees base. This allows for ( I believe but shaun or someone would know for sure) a total of 34 degrees of timing. Set base to 12, total timing is 32...the consant is 20 but instead of weights and springs and centrifugals, its the eec that controls it in conjunction with tfi etc.
Well when you put this plug BACK in, watch your timing light. That fucker will go up to 19-22 degrees of initial timing, while sitting there idling.
quote:
Originally posted by turbo50:
quote:
Originally posted by wilit:
I tried constant on my '68 and it ran like crap. I've read it should be on constant, but smog rules made it more efficient on ported. Not sure if that's true, but just what I've read.
Lets touch on this. Hopefully this post gets moved to tech section. Sorry to hijack, CODY.
Most vacuum advance canisters arent deployed until about 15hg of vacuum or so. What this does in a cammed or modified engine is cause the can to deploy and undeploy or not deploy or deploy too early etc etc.
So it ran like shit, idled like shit, you took it off.
Well now you are stuck with a "tune" essentially that is like locking your timing out with a stock eec (no spout in) this works great under ONE condition. WIDE OPEN throttle.
Thats it. Sucks at idle, part throttle suffers cooling effects in chamber, suffers MPG makes your eyes water. Just sux.
The fix? Would have been, probably will BE because I know Willits and your tech abilities. Put a dizzy back on that has vacuum advance and buy and adjustable canister AFTER you put a vacuum gauge on and get a rough idea of idle vacuum and part throttle vacuum values.
Here is an example. DONT spend $58 bucks on one but you see:
http://www.ebay.com/itm/Crane-Cams-Distributor-Advance-Vacuum-Adjustable-Ford-Electronic-Ignition-Kit-/390483981453?forcev4exp=true&forceRpt=true#vi-content
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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Duncan Motors
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Member # 7045
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posted
theres a better artical to read this info on but hell if i know where. many different factors for many different advantages. to narrow them down a bit, i could help u better if i knew the application, motor specs and whats your agenda?
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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Duncan Motors
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Member # 7045
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the vacuum questions is telling me that u have a vac distributor? well ported vacuum is closed at idle due to the vac source is above the throttle plates on the carb, so no vac till the throttle opens. then full vacuum is normally below the throttle plates where vac is all the time. now are u wondering if u want full vacuum or ported?
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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wilit
Mustang Messiah
Member # 3367
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posted
quote:
Originally posted by turbo50:
The reason your car ran like shit with it setup is because you didnt spend enough time or werent fully educated with its function, IMHO.
Exactly both. I read a bunch of articles about it, tried it, didn't work and swapped it back. Having a timing light with the advance knob on it so I could figure out total timing would have helped. Pretty sure a recurve of the distributor would be in order.
quote:
Originally posted by turbo50:
The fix? Would have been, probably will BE because I know Willits and your tech abilities. Put a dizzy back on that has vacuum advance and buy and adjustable canister AFTER you put a vacuum gauge on and get a rough idea of idle vacuum and part throttle vacuum values
Thanks. I have enough ability to assemble stuff. Tuning and getting it to run correctly is a whole nuther dark art I'm working on.
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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turbo50
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Member # 6700
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posted
quote:
Originally posted by Duncan Motors:
the vacuum questions is telling me that u have a vac distributor? well ported vacuum is closed at idle due to the vac source is above the throttle plates on the carb, so no vac till the throttle opens. then full vacuum is normally below the throttle plates where vac is all the time. now are u wondering if u want full vacuum or ported?
I love you Jon.
He had just posted a pic of his motor and I noticed a dizzy with no vacuum hose to the advance unit.
I suggested, cuz I like the kid and want to see him get the best out of his combo, which is low buck and he has put a lot of blood,sweat and tears into along with some dollars.
Having been in his shoes once, I suggested he run vacuum to it, constant and then I got off on a tangent.
There are TONS of better articles out there written by pros and engineers. This was just my ooog ooog fred flinstone style cave man approach to it.
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.........when was the last time YOU built something with YOUR own hands?
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Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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Duncan Motors
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Member # 7045
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posted
hmmm general rule of thumb for me is, gotta know and love your timing light for this stuff. but bottom rules are. u gota have base timing, and the timing advance, either weighted, or vac assisted, can not exceed your full max timing u desire.
most motors do not exceed 35 degrees total. so if your vac advance if on a ported set up is 15 degrees fully open, then the internal weights advance another 15, but your base timing is 10, total timing u will have 40, 5 to much. so they make kits that can adjust the vac pod on the distributor, and they make a adjust weights and springs for the internal advance set up.
so first u gotta figure out where u want your timing to be <base, advance at what rpm,then total>. then check to see what u got on your set up, then choose which way u wanna adjust with your set up.
to check get a timing light, one that reads rpm is a more desirable one. start it up with no vac hooked up on the dis, whats your base timing? <mark that in the memory banks, lets say it ten. then start to rev your motor slowly up as u watch your timing mark, lets say at 2500 your timing starts to advance <mark that in the memory banks>. continue to to increase the rpm of the motor till the timing stops advancing, how much has the timing increased? <write that in the memory banks> but lets say it advanced another ten. now let the motor idle down. when its idling watch the timing pointer as u hook up the vacuum advance to a full time vac source, it should advance immediately, and how much did timing advance then? < write that down in the memory banks>.
now with that set up we had base timing was at ten, internal advance started at 2500 to advance another ten, and the vacuum ported or not is another ten, for a total of 30 degrees at wide open throttle. and the internal kit or vac is to change those where u want them to advance at what rpm, and how much.
some guys dont run a vac, or internal , and just run full max timing full time, but it gets hard on your starter. or they switch that around in any order to achieve want they want. i normally make sure full timing right before the power curve of the cam has started.
again your parts, motor, and specs for what i listed would help me help u a bit more.
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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Duncan Motors
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Member # 7045
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i didnt know what was going on but willit has helped me many times, beside just being generally help full. hope something i wrote can help as well.
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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BIGBALLFACTOR
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Member # 7277
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posted
Only i have to say dont use a dial timing light to check total timing if dont have a stock ignition system becuase if do your not going to like how things end
Posts: 6908 | From: okc | Registered: Dec 2006
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turbo50
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Member # 6700
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posted
quote:
Originally posted by Duncan Motors:
hmmm general rule of thumb for me is, gotta know and love your timing light for this stuff. but bottom rules are. u gota have base timing, and the timing advance, either weighted, or vac assisted, can not exceed your full max timing u desire.
most motors do not exceed 35 degrees total. so if your vac advance if on a ported set up is 15 degrees fully open, then the internal weights advance another 15, but your base timing is 10, total timing u will have 40, 5 to much. so they make kits that can adjust the vac pod on the distributor, and they make a adjust weights and springs for the internal advance set up.
so first u gotta figure out where u want your timing to be <base, advance at what rpm,then total>. then check to see what u got on your set up, then choose which way u wanna adjust with your set up.
to check get a timing light, one that reads rpm is a more desirable one. start it up with no vac hooked up on the dis, whats your base timing? <mark that in the memory banks, lets say it ten. then start to rev your motor slowly up as u watch your timing mark, lets say at 2500 your timing starts to advance <mark that in the memory banks>. continue to to increase the rpm of the motor till the timing stops advancing, how much has the timing increased? <write that in the memory banks> but lets say it advanced another ten. now let the motor idle down. when its idling watch the timing pointer as u hook up the vacuum advance to a full time vac source, it should advance immediately, and how much did timing advance then? < write that down in the memory banks>.
now with that set up we had base timing was at ten, internal advance started at 2500 to advance another ten, and the vacuum ported or not is another ten, for a total of 30 degrees at wide open throttle. and the internal kit or vac is to change those where u want them to advance at what rpm, and how much.
some guys dont run a vac, or internal , and just run full max timing full time, but it gets hard on your starter. or they switch that around in any order to achieve want they want. i normally make sure full timing right before the power curve of the cam has started.
again your parts, motor, and specs for what i listed would help me help u a bit more.
You are in correct.
The ignition timing added by a vaccun advance system, ported or manifold has nothing to do with total timing as at wide open throttle, under load reading and ANY ignition advance added to base will be pulled when the motor sees no vacuum, ie under load or wide open....
Read my example again.
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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turbo50
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Member # 6700
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posted
quote:
Originally posted by Duncan Motors:
most motors do not exceed 35 degrees total. so if your vac advance if on a ported set up is 15 degrees fully open, then the internal weights advance another 15, but your base timing is 10, total timing u will have 40, 5 to much. so they make kits that can adjust the vac pod on the distributor, and they make a adjust weights and springs for the internal advance set up.
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You been tunin wrong then. Once you have enough rpm to get the weights out, under laod or wot the timing (15 as an example) provided by any ported or manifold source will GO AWAY there will be NO vacuum provided by the motor at this time. So u then have base say 10 and your weights say 15 for a total of 25 at load and wide open and then at part throttle or idle you have up to 40, JUST like an eec typically does.
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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Duncan Motors
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Member # 7045
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posted
10 base, with the weights another ten, would only be 20 full open, then the vac at ten would be another 30 im thinking. your saying the vac goes away at high rpm where the timing would be back at 20 full open? i understand in theory of the vac would go away on a gauge, but i don't believe it works that way at the carb main throat, i could be wrong? this was how i was always taught, and has always added up in the final number of all three in the end of my checks at wide throttle, or high enough for the weights to fully open. i check them when they aren't loaded or under load, but vac shouldn't change under load if i read correctly? but i do get the final number i desire of total timing in the end doing it this way? lol hope im not to tired after my long day and im extremly missing sumthing lo. gd night ill prob dream about this now
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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norcalfiddy
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Member # 11207
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posted
quote:
Originally posted by turbo50:
quote:
Originally posted by Duncan Motors:
the vacuum questions is telling me that u have a vac distributor? well ported vacuum is closed at idle due to the vac source is above the throttle plates on the carb, so no vac till the throttle opens. then full vacuum is normally below the throttle plates where vac is all the time. now are u wondering if u want full vacuum or ported?
I love you Jon.
He had just posted a pic of his motor and I noticed a dizzy with no vacuum hose to the advance unit.
I suggested, cuz I like the kid and want to see him get the best out of his combo, which is low buck and he has put a lot of blood,sweat and tears into along with some dollars.
Having been in his shoes once, I suggested he run vacuum to it, constant and then I got off on a tangent.
There are TONS of better articles out there written by pros and engineers. This was just my ooog ooog fred flinstone style cave man approach to it.
So dan, you recommend me to run constant vac source? Where would I find a constant source? The carb?
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600HP 1996 7.3L powerstroke single cab short bed race truck
Posts: 3393 | From: Brentwood | Registered: Aug 2011
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turbo50
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Member # 6700
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posted
quote:
Originally posted by 4IDFOX:
Read this.
http://classicinlines.com/VacAdvance.asp
And this
http://vb.foureyedpride.com/showthread.php?t=22229
Ya thanks, they support my statement.
Also support my preference for manifold vacuum because ported source not gonna be there at idle.....
Cody, constant vacuum is right off the manifold or on the carb anywhere below the butterflies
--------------------
.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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Duncan Motors
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Member # 7045
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posted
this a trip, theres been a lot of cars where if i had the vacuum advance hooked up the car would ping on acceleration, and if i just unhooked it, it would take the timing out and not ping no more, been proven on the timing light under inspection many a time as well. ive always hooked the vac to the ported side of the carb. im gona do some reading
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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turbo50
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Member # 6700
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posted
quote:
Originally posted by Duncan Motors:
this a trip, theres been a lot of cars where if i had the vacuum advance hooked up the car would ping on acceleration, and if i just unhooked it, it would take the timing out and not ping no more, been proven on the timing light under inspection many a time as well. ive always hooked the vac to the ported side of the carb. im gona do some reading
will still make a small amount of vacuum under light acceleration in a handful of situations and if you have wrong or improper adjusted vacuum canister then yes I see this could happen
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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wilit
Mustang Messiah
Member # 3367
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posted
OMG, Turbo50, I can't thank you enough. It's like I'm driving a completely different car. It's incredible. I wish I had posted this question a long time ago.
Also, in case anyone is curious, if you have a stock Ford distributor with a vacuum advance can that has a hex shape on the end, it has an adjustable diaphragm. No need to use the Crane one. Ford distributors also have an advance cam that is semi-adjustable. There are several different cams out there with id's like 13L on one end and 15L on the other. This is the total advance limit. So if you have a 13L, that's 13x2=26° total advance. 15L would be 30°. Here's a pic of what it looks like.
You can remove the cam and swap it between the two to limit the amount of total advance. Pretty awesome Ford included these features from the factory.
[ November 04, 2012, 08:09 PM: Message edited by: wilit ]
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"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
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turbo50
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Member # 6700
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posted
quote:
Originally posted by wilit:
OMG, Turbo50, I can't thank you enough. It's like I'm driving a completely different car. It's incredible. I wish I had posted this question a long time ago.
Also, in case anyone is curious, if you have a stock Ford distributor with a vacuum advance can that has a hex shape on the end, it has an adjustable diaphragm. No need to use the Crane one. Ford distributors also have an advance cam that is semi-adjustable. There are several different cams out there with id's like 13L on one end and 15L on the other. This is the total advance limit. So if you have a 13L, that's 13x2=26° total advance. 15L would be 30°. Here's a pic of what it looks like.
You can remove the cam and swap it between the two to limit the amount of total advance. Pretty awesome Ford included these features from the factory.
Dude, just helpin another enthusiast out and you sayin thanks and weedin thru the bullshit is enuff for me!
Yes, the arms and diaprahm I also knew about but didn't want to add to any confusion.
Hopefully Cody sees this cuz he is like you and very mechanically inclined.
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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4IDFOX
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Member # 9921
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posted
quote:
Originally posted by Duncan Motors:
this a trip, theres been a lot of cars where if i had the vacuum advance hooked up the car would ping on acceleration, and if i just unhooked it, it would take the timing out and not ping no more, been proven on the timing light under inspection many a time as well. ive always hooked the vac to the ported side of the carb. im gona do some reading
Just hooking up to ported vacuum and not getting the results you wanted does not mean it does not work. You halve to tune it.
I have a 11-1 460 in my truck that I run on 91 octaine. With a tuned duraspark that does not ping while towing 7000#
Wilit has figured this out
Read the foureyed link that I posted. Read all of it. It will walk you through tuning a dizzy.
[ November 04, 2012, 10:01 PM: Message edited by: 4IDFOX ]
Posts: 375 | From: Redding CA | Registered: Apr 2010
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norcalfiddy
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Member # 11207
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posted
quote:
Originally posted by turbo50:
quote:
Originally posted by wilit:
OMG, Turbo50, I can't thank you enough. It's like I'm driving a completely different car. It's incredible. I wish I had posted this question a long time ago.
Also, in case anyone is curious, if you have a stock Ford distributor with a vacuum advance can that has a hex shape on the end, it has an adjustable diaphragm. No need to use the Crane one. Ford distributors also have an advance cam that is semi-adjustable. There are several different cams out there with id's like 13L on one end and 15L on the other. This is the total advance limit. So if you have a 13L, that's 13x2=26° total advance. 15L would be 30°. Here's a pic of what it looks like.
You can remove the cam and swap it between the two to limit the amount of total advance. Pretty awesome Ford included these features from the factory.
Dude, just helpin another enthusiast out and you sayin thanks and weedin thru the bullshit is enuff for me!
Yes, the arms and diaprahm I also knew about but didn't want to add to any confusion.
Hopefully Cody sees this cuz he is like you and very mechanically inclined.
Sweet ill have to check mine out and see what works best
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600HP 1996 7.3L powerstroke single cab short bed race truck
Posts: 3393 | From: Brentwood | Registered: Aug 2011
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