vaccum advance on hei not connected
#1
vaccum advance on hei not connected
Search around for a while now and couldn't really find any situation similar so any help would be appreciated.
Just purchased a 1970 Cutlass with 350 olds motor. Always wanted one of these so pretty excited to finally have one.
The setup on the 350 is a bit modified, has a performer 350 intake headers and a 750 holley. hei has also been installed. Upon close inspection I noticed that the vacuum advance on the hei is not connected anywhere and there is no available hose. Was wondering if anyone could recommend the best place to share vaccum. I was leaning towards sharing off the carb.
could this be causing a loss in power?
Just purchased a 1970 Cutlass with 350 olds motor. Always wanted one of these so pretty excited to finally have one.
The setup on the 350 is a bit modified, has a performer 350 intake headers and a 750 holley. hei has also been installed. Upon close inspection I noticed that the vacuum advance on the hei is not connected anywhere and there is no available hose. Was wondering if anyone could recommend the best place to share vaccum. I was leaning towards sharing off the carb.
could this be causing a loss in power?
#2
could this be causing a loss in power?
I believe manifold vacuum was used in 1970 for the distributor.
#4
Advance uses "ported" vacuum, as shown in the following image:
Everything else uses direct manifold vacuum.
No.
Olds never used manifold vacuum for ignition advance.
Norm
Everything else uses direct manifold vacuum.
No.
Norm
#6
Olds never used manifold vacuum for ignition advance.
http://static.summitracing.com/globa...s/edl-1411.pdf
#7
OLds64 is correct, manifold was original. The change to ported vacuum from manifold vacuum was for emissions reasons.
Remember this??
Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.
If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.
What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.
Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.
Remember this??
Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.
If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.
What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.
Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.
#9
NOT an internet myth. Read yet another article:
The second method used to advance the ignition timing is called vacuum timing advance. This method is almost always used in addition to mechanical timing advance. It generally increases fuel economy and driveability, particularly at lean mixtures. Vacuum advance works by using a manifold vacuum source to advance the timing at low to mid engine load conditions by rotating the position sensor (contact points, hall effect or optical sensor, reluctor stator, etc) mounting plate in the distributor with respect to the distributor shaft. Vacuum advance is diminished at wide open throttle (WOT), causing the timing advance to return to the base advance in addition to the mechanical advance.
One source for vacuum advance is a small opening located in the wall of the throttle body or carburetor adjacent to but slightly upstream of the edge of the throttle plate. This is called a ported vacuum. The effect of having the opening here is that there is little or no vacuum at idle. Other vehicles use vacuum directly from the intake manifold. This provides full engine vacuum (and hence, full vacuum advance) at idle.
On some vehicles, a temperature sensing switch will apply manifold vacuum to the vacuum advance system when the engine is hot or cold, and ported vacuum at normal operating temperature. This is a version of emissions control; the ported vacuum allowed carburetor adjustments for a leaner idle mixture. At high engine temperature, the increased advance raised engine speed to allow the cooling system to operate more efficiently. At low temperature the advance allowed the enriched warm-up mixture to burn more completely, providing better cold-engine running.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum.
This is a well working reality for my Olds.
The second method used to advance the ignition timing is called vacuum timing advance. This method is almost always used in addition to mechanical timing advance. It generally increases fuel economy and driveability, particularly at lean mixtures. Vacuum advance works by using a manifold vacuum source to advance the timing at low to mid engine load conditions by rotating the position sensor (contact points, hall effect or optical sensor, reluctor stator, etc) mounting plate in the distributor with respect to the distributor shaft. Vacuum advance is diminished at wide open throttle (WOT), causing the timing advance to return to the base advance in addition to the mechanical advance.
One source for vacuum advance is a small opening located in the wall of the throttle body or carburetor adjacent to but slightly upstream of the edge of the throttle plate. This is called a ported vacuum. The effect of having the opening here is that there is little or no vacuum at idle. Other vehicles use vacuum directly from the intake manifold. This provides full engine vacuum (and hence, full vacuum advance) at idle.
On some vehicles, a temperature sensing switch will apply manifold vacuum to the vacuum advance system when the engine is hot or cold, and ported vacuum at normal operating temperature. This is a version of emissions control; the ported vacuum allowed carburetor adjustments for a leaner idle mixture. At high engine temperature, the increased advance raised engine speed to allow the cooling system to operate more efficiently. At low temperature the advance allowed the enriched warm-up mixture to burn more completely, providing better cold-engine running.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum.
This is a well working reality for my Olds.
#10
[B]NOT [/B]an internet myth. Read yet another article:
The second method used to advance the ignition timing is called vacuum timing advance. This method is almost always used in addition to mechanical timing advance. It generally increases fuel economy and driveability, particularly at lean mixtures. Vacuum advance works by using a [URL="https://classicoldsmobile.com/wiki/Manifold_vacuum"][COLOR=#0645ad]manifold vacuum[/COLOR][/URL] source to advance the timing at low to mid engine load conditions by rotating the position sensor (contact points, hall effect or optical sensor, reluctor stator, etc) mounting plate in the distributor with respect to the distributor shaft. Vacuum advance is diminished at [URL="https://classicoldsmobile.com/wiki/Wide_open_throttle"][COLOR=#0645ad]wide open throttle[/COLOR][/URL] (WOT), causing the timing advance to return to the base advance in addition to the mechanical advance.
One source for vacuum advance is a small opening located in the wall of the [URL="https://classicoldsmobile.com/wiki/Throttle_body"][COLOR=#0645ad]throttle body[/COLOR][/URL] or [URL="https://classicoldsmobile.com/wiki/Carburetor"][COLOR=#0645ad]carburetor[/COLOR][/URL] adjacent to but slightly upstream of the edge of the [URL="https://classicoldsmobile.com/wiki/Throttle_plate"][COLOR=#0645ad]throttle plate[/COLOR][/URL]. This is called a [URL="https://classicoldsmobile.com/w/index.php?title=Ported_vacuum&action=edit&redlink= 1"][COLOR=#ba0000]ported vacuum[/COLOR][/URL]. The effect of having the opening here is that there is little or no vacuum at idle. Other vehicles use vacuum directly from the intake manifold. This provides full engine vacuum (and hence, full vacuum advance) at idle.
On some vehicles, a temperature sensing switch will apply manifold vacuum to the vacuum advance system when the engine is hot or cold, [B]and ported vacuum at normal [/B][URL="https://classicoldsmobile.com/wiki/Operating_temperature"][COLOR=#0645ad][B]operating temperature[/B][/COLOR][/URL][B]. This is a version of emissions control;[/B] the ported vacuum allowed carburetor adjustments for a leaner idle mixture. At high engine temperature, the increased advance raised engine speed to allow the cooling system to operate more efficiently. At low temperature the advance allowed the enriched warm-up mixture to burn more completely, providing better cold-engine running.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum.
This is a well working [B]reality[/B] for my Olds.
The second method used to advance the ignition timing is called vacuum timing advance. This method is almost always used in addition to mechanical timing advance. It generally increases fuel economy and driveability, particularly at lean mixtures. Vacuum advance works by using a [URL="https://classicoldsmobile.com/wiki/Manifold_vacuum"][COLOR=#0645ad]manifold vacuum[/COLOR][/URL] source to advance the timing at low to mid engine load conditions by rotating the position sensor (contact points, hall effect or optical sensor, reluctor stator, etc) mounting plate in the distributor with respect to the distributor shaft. Vacuum advance is diminished at [URL="https://classicoldsmobile.com/wiki/Wide_open_throttle"][COLOR=#0645ad]wide open throttle[/COLOR][/URL] (WOT), causing the timing advance to return to the base advance in addition to the mechanical advance.
One source for vacuum advance is a small opening located in the wall of the [URL="https://classicoldsmobile.com/wiki/Throttle_body"][COLOR=#0645ad]throttle body[/COLOR][/URL] or [URL="https://classicoldsmobile.com/wiki/Carburetor"][COLOR=#0645ad]carburetor[/COLOR][/URL] adjacent to but slightly upstream of the edge of the [URL="https://classicoldsmobile.com/wiki/Throttle_plate"][COLOR=#0645ad]throttle plate[/COLOR][/URL]. This is called a [URL="https://classicoldsmobile.com/w/index.php?title=Ported_vacuum&action=edit&redlink= 1"][COLOR=#ba0000]ported vacuum[/COLOR][/URL]. The effect of having the opening here is that there is little or no vacuum at idle. Other vehicles use vacuum directly from the intake manifold. This provides full engine vacuum (and hence, full vacuum advance) at idle.
On some vehicles, a temperature sensing switch will apply manifold vacuum to the vacuum advance system when the engine is hot or cold, [B]and ported vacuum at normal [/B][URL="https://classicoldsmobile.com/wiki/Operating_temperature"][COLOR=#0645ad][B]operating temperature[/B][/COLOR][/URL][B]. This is a version of emissions control;[/B] the ported vacuum allowed carburetor adjustments for a leaner idle mixture. At high engine temperature, the increased advance raised engine speed to allow the cooling system to operate more efficiently. At low temperature the advance allowed the enriched warm-up mixture to burn more completely, providing better cold-engine running.
For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum.
This is a well working [B]reality[/B] for my Olds.
Link to the webpage, then quote the part you wish me to respond to.
Norm
#12
Norm,
I have read the posts you referred me to. Sounded like two people simply going around in circles.
The post I have written above was to show that the "Emissions" point regarding the switch from manifold vacuum to ported vacuum was not a myth as you think. There was a change in gasoline (leaded vs unleaded, as well as stricter EPA standards on cars)--that was the "emissions" part of the post above referring to why ported vacuum was being used and not manifold vacuum, which had been used previously.I thought this was general knowledge, so for me to repeat it, I'm assuming you will just deny it, no matter how many tech articles I post, and no matter who they are written by. So, to avoid more "Circular" arguementation I'm going to let the words I've posted stand on their own merit and let the individual who began this post research the validity of my statements and do some more research on the web if they so choose. Otherwise, I sense that we will just post back and forth with the typical "yes it is", "no it isn't" which in the end goes nowhere.
I have read the posts you referred me to. Sounded like two people simply going around in circles.
The post I have written above was to show that the "Emissions" point regarding the switch from manifold vacuum to ported vacuum was not a myth as you think. There was a change in gasoline (leaded vs unleaded, as well as stricter EPA standards on cars)--that was the "emissions" part of the post above referring to why ported vacuum was being used and not manifold vacuum, which had been used previously.I thought this was general knowledge, so for me to repeat it, I'm assuming you will just deny it, no matter how many tech articles I post, and no matter who they are written by. So, to avoid more "Circular" arguementation I'm going to let the words I've posted stand on their own merit and let the individual who began this post research the validity of my statements and do some more research on the web if they so choose. Otherwise, I sense that we will just post back and forth with the typical "yes it is", "no it isn't" which in the end goes nowhere.
#13
Then, when challenged, I backed it up with the following:
To clarify:
Originally Posted by 1949 Olds Shop Manual
The vacuum controlled advance mechanism consists of a spring loaded diaphragm linked to the distributor breaker plate which is mounted on three ball bearings. Vacuum for operating this advance mechanism is taken from the carburetor riser just above the throttle valve, preventing spark advance while the engine is idling.
I am also well aware that it is. If it was not "common knowledge" it would not be a myth.
If you have anything of substance, show it. If you do not, just say so.
Norm
#14
Norm,
Why go in circles? First off, you DO NOT own factory manuals for every make and model of Olds from 1935 so you do not know the actual answer by using manuals as you suggest. Second, the gasoline/EPA regulations has EVERYTHING to do with the emissions change, and vacuum change-- you just don't understand it. It's obvious you believe every tech person on earth is wrong and that only you have credible things to say. As I posted, this is how you operate and I cannot change your mind no matter how many articles and technicians disprove your thoughts. You refer to professional tech articles as "Assumptions" or "baseless"...I'm sure Smokey Yunick will find that amusing. It's a wonder you're not known throughout the country or a millionaire from the knowledge you claim to possess.
I know it's a waste of time but here's another tech article explaining the change I've already described 3 times. I'm even posting a you tube link where the tech repeats again the change from manifold vacuum to ported vacuum on EMISSIONS cars (from 38 seconds to 58 seconds, he clearly states that early muscle cars used Manifold vacuum, and only when emissions came into play did the switch to ported take place). I know, I know, you'll read the article below, watch the youtube video with the older gentleman and tell me you're smarter than these techs too...
G77rvd--since you posted this thread to begin with,, I hope you're getting all this info, so you can make your decision.
Early, pre-emission vacuum advance units were typically linked to a manifold vacuum source. This meant that the vacuum was most often taken from a location below the carburetor throttle body. During idle and part throttle operation, manifold vacuum is high. This advances the ignition timing under those conditions and improves fuel economy. When the engine is operated at wide-open throttle, manifold vacuum is low. This means the vacuum mechanism does not advance ignition timing. As a result, there is no chance of detonation (or pinging). In the mid-'60s, vacuum advance mechanisms changed to suit emission requirements. The vacuum source was changed from the manifold to the carburetor venturi. This is called "spark ported vacuum." Spark ported vacuum is lowest at idle, and then increases as the throttle is opened. This is completely opposite to manifold vacuum.
http://www.youtube.com/watch?v=Gj2utt1oSQE&feature=related
Why go in circles? First off, you DO NOT own factory manuals for every make and model of Olds from 1935 so you do not know the actual answer by using manuals as you suggest. Second, the gasoline/EPA regulations has EVERYTHING to do with the emissions change, and vacuum change-- you just don't understand it. It's obvious you believe every tech person on earth is wrong and that only you have credible things to say. As I posted, this is how you operate and I cannot change your mind no matter how many articles and technicians disprove your thoughts. You refer to professional tech articles as "Assumptions" or "baseless"...I'm sure Smokey Yunick will find that amusing. It's a wonder you're not known throughout the country or a millionaire from the knowledge you claim to possess.
I know it's a waste of time but here's another tech article explaining the change I've already described 3 times. I'm even posting a you tube link where the tech repeats again the change from manifold vacuum to ported vacuum on EMISSIONS cars (from 38 seconds to 58 seconds, he clearly states that early muscle cars used Manifold vacuum, and only when emissions came into play did the switch to ported take place). I know, I know, you'll read the article below, watch the youtube video with the older gentleman and tell me you're smarter than these techs too...
G77rvd--since you posted this thread to begin with,, I hope you're getting all this info, so you can make your decision.
Early, pre-emission vacuum advance units were typically linked to a manifold vacuum source. This meant that the vacuum was most often taken from a location below the carburetor throttle body. During idle and part throttle operation, manifold vacuum is high. This advances the ignition timing under those conditions and improves fuel economy. When the engine is operated at wide-open throttle, manifold vacuum is low. This means the vacuum mechanism does not advance ignition timing. As a result, there is no chance of detonation (or pinging). In the mid-'60s, vacuum advance mechanisms changed to suit emission requirements. The vacuum source was changed from the manifold to the carburetor venturi. This is called "spark ported vacuum." Spark ported vacuum is lowest at idle, and then increases as the throttle is opened. This is completely opposite to manifold vacuum.
http://www.youtube.com/watch?v=Gj2utt1oSQE&feature=related
Last edited by 71 Cutlass; August 14th, 2010 at 10:18 PM.
#15
Repeating my statement,
your challenge,
and your most recent "defense".
You have not shown a link to any "tech article". Instead, you have been copying opinions from forum discussions.
Good choice. For the most accurate information, YouTube is second only to Wikipedia.
Continuing the actual discussion:
Norm
Good choice. For the most accurate information, YouTube is second only to Wikipedia.
Continuing the actual discussion:
- Manifold vacuum was only added via TVS, which has been discussed elsewhere.
- If "ported vacuum" was not used until 1966, how is it that it was used in 1949?
Norm
Last edited by 88 coupe; August 15th, 2010 at 12:43 PM.
#16
Can I predict exactly or what...Norm ignored everything no matter how clear and obvious. And these are tech articles Norm not opinions from boards...again you're flat out wrong. So in honor of this discussion, may I direct you to "Will it go round in circles" a live video by Eric Clapton and Billy Preston, performing that 70s top 10 hit. It's actually pretty good. click the link http://www.youtube.com/watch?v=6NYIfUY-Gvs
Last edited by 71 Cutlass; August 15th, 2010 at 07:22 PM.
#17
http://www.nizkor.org/features/falla...d-herring.html
It is a simple question. If you cannot answer it, just say so.
Norm
Norm
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