Just for clarity. The only difference between ported and manifold vacuum is that manifold vacuum gives you vacuum at idle and therefore, timing advance at idle. If you’re hooked to ported vacuum you will not have any vacuum at idle. Therefore you will have no timing advance at idle. Only when you begin to step on the throttle will vacuum come in and timing will begin to advance. So if you set your initial timing while hooked up to manifold vacuum and you want to switch to ported vacuum you will have to increase your initial timing because when you disconnect from manifold vacuum you’re taking away some advance timing the canister added at idle. If you’re driving a vehicle with a stock to mild cam I would suggest using ported vacuum advance. A more radical engine with a big cam will benefit from manifold vacuum advance. There are lots of videos and articles on vacuum advance out there and most are very vague. Hope this helps.
Vacuum advance at idle gives a more efficient idle, which is important in traffic jams, and reduces plug fouling at idle, so I use manifold vacuum with my stock cam, though my worn engine has reduced compression at idle.
I agree with your statement: "There are lots of videos and articles on vacuum advance out there and most are very vague" I have found NONE that adequately discuss the issue as you have here. My big issue is I see the signals being 180 degrees different : With Ported vacuum your signal is zero at idle and goes to vacuum with throttle opening. With manifold vacuum you start with a vacuum signal and it goes even lower with throttle opening. I think I just identified my reasoning problem here........ I'll get back to you. Thank you for posting I believe I just learned something.
@@28704joe One could just keep bumping it up every week or so until you get a sign that something is too hot, like hearing spark knock or seeing a really hot spark plug, but one can do the same with base timing too, except I can't because my engine has lost so much compression with wear that it still runs cool with the base timing so far advanced that it tries to start backwards, straining the starter motor, so that leaves me with vacuum and centrifugal advance, but even without natural disasters, I idle enough to want an efficient idle and so use manifold vacuum. I also don't want the plugs to foul while idling.
Great video. But I too agree with Craig. If using ported vac there will be no pull on the distributor until you begin adding throttle. So, if someone wants to keep attached to ported vac (as a lot of people feel is appropriate), do I set my initial timing to the manufacturer's specs? Or do I need to add additional timing as Craig suggests. This is in a Ford 460 that has been rebuilt. Pretty much stock. And, I can't seem to dial the vac canister below 15. Are some vac cans made to require more vac than others? I would think it would be able to dial it down to 10 or so ......at least.
Thanks for this. I have been fine adjusting the idle vacuum advance on my crate 350. And you just accidentally reminded me that my actual condition needs to be set while in gear. My car has an automatic transmission, with a pretty sturdy converter.
Incredibly helpful video, thank you for recording it! When adjusting these canisters with an allen key, in your experience does the screw/adjustment "lock out" at some point (i.e it cannot be turned any further)? Like another commenter, no matter what allen key I use I'm either unable to get a bite on it or the screw/adjuster is just spinning in place.
Great video. Very simple & quick. Do you remember what adjustable vacuum can is reliable (Brand / Part #)? I also read that if the can is not fully working this can affect your mpg? How so? Thanks
@@28704joe You want vacuum advance at idle to have a clean and efficient idle, since there is little danger of spark knock at idle. Without it, you run the risk of running out of gas in huge traffic jams associated with disasters like Katrina.
My 350 chevy small block is hooked to only manifold vaccum. I tuned it to 12 degrees tdc. When I place vaccum gauge the best I could get to tune is at 14 gh vac. Any suggestions? And if I open timed vaccum from distributor will that increase that number?
This is a great way to explain how this vac advance works. I purchased an 87 Starion that has Vac Ad and it has a misfire under wot. It pops and leans out on my af as my foot goes down. It was making over 18lbs of boost and suddenly, can't get past 5 or 6 without a band and pop. Could my vac ad be out of whack? Haven't changed the plugs nor the distributor yet. I plan on checking the vac ad to see if it holds pressure... At idle, I feel no suction on that line and it goes right to the throttle body. Any suggestions would be great!
I'm really curious I have my vacuum advance coming off my distributor on the side of my carburetor. Should I be hooked up to the manifold vacuum for this to work correctly
I hook mine to the baseplate on the carb but it's a manifold vacuum port. some carb ports will not give you full engine vacuum and I set all my vacuum advance cannisters to manifold vacuum you want the same vacuum you measure with a vacuum gauge . to set your cannister.
I'm pretty sure if you match the vacuum advance to the max vacuum of the engine, you will get pre-detonation (pinging). The vacuum advance canister only comes into play at idle. It should be set to 8 degrees max. Maybe someone more experienced can chime in.
unported manifold vacuum at the base of the carb but sometimes I will use ported carb vacuum on certain situations. A lot of factory muscle cars had ported vacuum at the carb for the distributor vacuum advance. As described in the video you can check these parameters in ported or unported situation’s and adjust the vacuum advance accordingly.
@@pyleup I tried both and fine ported worked the best, no vacuum advance at idle and vacuum advance at part throttle. Manifold vacuum did the opposite which seem to defeat the purpose.
My 1977 Camaro (250 inline 6 automatic) has a dead spot / hesitation just off idle when I hit the gas pedal from stopped and when I hit the gas pedal from cruising. I’ll hit the accelerator and it momentarily feels like it’s going to stall before the car springs into action and then it runs fine Sometimes it causes the car to stall completely when I accelerate around a sharp corner or bend unless I coast it and accelerate gently. Could the vacuum advance cause this ? I’ve already had a carb rebuild , accelerator pump and new fuel pump.
Sounds more like a Carb problem. Check the vacuum advance canister to see if it's holding a vacuum and that it's plugged into a manifold vacuum port. Also check your base timing and make sure it's set between 10 and 12 degrees. Make sure the vacuum canister is unplugged when you check the timing.
The carb may have been rebuilt, but I'm wondering if it was properly adjusted - idle mixture settings and accelerator pump adjustments. What you are describing, the bog, sounds like a temporary lean fuel condition before the main jets are flowing enough gas for the engine to stabilize.
U forgot the No1 point . Vacuum advance occurs at light throttle steady state cruise ie between 27mph ---- 55mph . U set the xtra advance between these vacuum /road speed points . If u still have a very basic distributor u may need xtra advance pending your setup so either manifold or ported setup might be better for you . When u have standalone programmable timing idle timing and cruise advance can be what ever u want
Yes and that's the point of the video, if you have low vacuum at idle or the canister is bad it may not pull in at all or only half way, big cams can cause this .
@@pyleup So we want to adjust that canister screw so that there's barely any advance timing while idling because if there is none then there will be a flat spot or delay after hitting throttle.
No that’s not it , you want Full vacuum advance timing at idle not part or none of it ,the moment you hit the throttle vacuum will drop and vacuum advance timing will drop out then you will be running on centrifugal advance of the distributor and what ever that timing curve is up to it’s max like 30 to 35 degrees at 3000 rpms. Vacuum advance is only for idle it will make it easier to start and idle better off idle throttle will be better street running. So you want to adjust it so you have full vacuum advance timing at idle.
If you can,t adjust it a least you should be able to test it to see if it is working and at what vacuum it comes in at and test your vacuum on your 300 I6 . If it,s stock the only thing you need to worry about is if it works or not. The cannister can be bad. you need to pull a vacuum on it to see if it works.
Were you using an aftermarket distributor? I have a 300 i6 but am using an aftermarket HEI from Summit (SUM-850033). Same issue you had. The vacuum canister is supposedly adjustable but it seems I'm unable to get a bite on the allen key.
Every distributor will be different. If you test it with a vacuum tool you will know which way to turn it . But you have to be watching it with the distributor cap off, otherwise you will never know if you're doing it right or not. You can't just turn it cw or ccw without testing it. Some stock distributors can't be adjusted, but you can still verify that the advance is working by testing.
I have a '67 Cad deville w/429. Im having what feels like missing at acceleration 35 mph to 55 mph. Been told to replace dist but dont believe that is necessary? Im afraid its just a keep replacing parts to fix mindset. Im wondering about the vac advance? I got new part and when I pulled off old vac advance and found oil inside of it? Any idea why??
The vacuum advance canister may be leaking. The vacuum leak would pull in any oil from the surrounding area in the engine. If the vacuum advance canister doesn't hold a vacuum, it is bad.
The problem with having it hooked up to a manifold vacuum is that it pulls on the diaphragm all of the time thus shortening the life of the vacuum advance unit... If it was hooked to ported vacuum it would not pull 100% of the time.. just saying
Best video on RUclips on vacuum advance and I’ve been searching forever. Thank you.
Glad it was helpful!
Old video, but the best one on vaccuum advance. Thanks so much
Just for clarity. The only difference between ported and manifold vacuum is that manifold vacuum gives you vacuum at idle and therefore, timing advance at idle. If you’re hooked to ported vacuum you will not have any vacuum at idle. Therefore you will have no timing advance at idle. Only when you begin to step on the throttle will vacuum come in and timing will begin to advance. So if you set your initial timing while hooked up to manifold vacuum and you want to switch to ported vacuum you will have to increase your initial timing because when you disconnect from manifold vacuum you’re taking away some advance timing the canister added at idle. If you’re driving a vehicle with a stock to mild cam I would suggest using ported vacuum advance. A more radical engine with a big cam will benefit from manifold vacuum advance.
There are lots of videos and articles on vacuum advance out there and most are very vague. Hope this helps.
I agree with your statement.
Vacuum advance at idle gives a more efficient idle, which is important in traffic jams, and reduces plug fouling at idle, so I use manifold vacuum with my stock cam, though my worn engine has reduced compression at idle.
I agree with your statement:
"There are lots of videos and articles on vacuum advance out there and most are very vague"
I have found NONE that adequately discuss the issue as you have here.
My big issue is I see the signals being 180 degrees different :
With Ported vacuum your signal is zero at idle and goes to vacuum with throttle opening.
With manifold vacuum you start with a vacuum signal and it goes even lower with throttle opening.
I think I just identified my reasoning problem here........
I'll get back to you.
Thank you for posting I believe I just learned something.
@@28704joe One could just keep bumping it up every week or so until you get a sign that something is too hot, like hearing spark knock or seeing a really hot spark plug, but one can do the same with base timing too, except I can't because my engine has lost so much compression with wear that it still runs cool with the base timing so far advanced that it tries to start backwards, straining the starter motor, so that leaves me with vacuum and centrifugal advance, but even without natural disasters, I idle enough to want an efficient idle and so use manifold vacuum. I also don't want the plugs to foul while idling.
Great video. But I too agree with Craig. If using ported vac there will be no pull on the distributor until you begin adding throttle. So, if someone wants to keep attached to ported vac (as a lot of people feel is appropriate), do I set my initial timing to the manufacturer's specs? Or do I need to add additional timing as Craig suggests. This is in a Ford 460 that has been rebuilt. Pretty much stock. And, I can't seem to dial the vac canister below 15. Are some vac cans made to require more vac than others? I would think it would be able to dial it down to 10 or so ......at least.
Thanks for this. I have been fine adjusting the idle vacuum advance on my crate 350. And you just accidentally reminded me that my actual condition needs to be set while in gear. My car has an automatic transmission, with a pretty sturdy converter.
Great to hear!
Short and to the point love it
Thank you for your explanation. I enjoyed your explanation.
Glad you enjoyed it!
Incredibly helpful video, thank you for recording it! When adjusting these canisters with an allen key, in your experience does the screw/adjustment "lock out" at some point (i.e it cannot be turned any further)? Like another commenter, no matter what allen key I use I'm either unable to get a bite on it or the screw/adjuster is just spinning in place.
Not all can be adjusted.
Yours may not be adjustable.
Great video. Very simple & quick. Do you remember what adjustable vacuum can is reliable (Brand / Part #)? I also read that if the can is not fully working this can affect your mpg? How so? Thanks
Great video thanks.👍
No problem 👍
So, do you want it to be equal to the vacuum your engine is pulling at idle? Thank you for this video!
yes
which way do you turn the wrench to lesson the amount of vacuum that it takes to advance the timing?
clockwise worked on mine but I recommend retesting it with a meter to verify
@@pyleup ok thanks
@@pyleup So just to be sure,, the vacuum advance canister should be pulled in to the max at idle?
yes
@@28704joe You want vacuum advance at idle to have a clean and efficient idle, since there is little danger of spark knock at idle. Without it, you run the risk of running out of gas in huge traffic jams associated with disasters like Katrina.
you explained that great nice job
Thanks!
My 350 chevy small block is hooked to only manifold vaccum. I tuned it to 12 degrees tdc. When I place vaccum gauge the best I could get to tune is at 14 gh vac. Any suggestions? And if I open timed vaccum from distributor will that increase that number?
This is a great way to explain how this vac advance works. I purchased an 87 Starion that has Vac Ad and it has a misfire under wot. It pops and leans out on my af as my foot goes down. It was making over 18lbs of boost and suddenly, can't get past 5 or 6 without a band and pop. Could my vac ad be out of whack? Haven't changed the plugs nor the distributor yet.
I plan on checking the vac ad to see if it holds pressure... At idle, I feel no suction on that line and it goes right to the throttle body. Any suggestions would be great!
Vacuum advance should play no part when in boost . it's only at idle it has an effect.
@@pyleup OK... That's good to know.
So, your vacuum @ idle was 12-14. YOU set your vacuum canister to 10?
Yes, you want your canister to be pulled in before you reach your max vacuum that your engine produces
At idle, of course
iv seen a lot of vids and out of all of them this is the best one i seen on how to set your adj vacuume canister very well explained
Thanks
I'm really curious I have my vacuum advance coming off my distributor on the side of my carburetor. Should I be hooked up to the manifold vacuum for this to work correctly
I hook mine to the baseplate on the carb but it's a manifold vacuum port. some carb ports will not give you full engine vacuum and I set all my vacuum advance cannisters to manifold vacuum you want the same vacuum you measure with a vacuum gauge . to set your cannister.
I'm pretty sure if you match the vacuum advance to the max vacuum of the engine, you will get pre-detonation (pinging). The vacuum advance canister only comes into play at idle. It should be set to 8 degrees max. Maybe someone more experienced can chime in.
This number 13 is that the amount of vacuum in drive or park?
Park
Do you use the ported or unported for the vacuum advance?
unported manifold vacuum at the base of the carb but sometimes I will use ported carb vacuum on certain situations. A lot of factory muscle cars had ported vacuum at the carb for the distributor vacuum advance. As described in the video you can check these parameters in ported or unported situation’s and adjust the vacuum advance accordingly.
@@pyleup I tried both and fine ported worked the best, no vacuum advance at idle and vacuum advance at part throttle. Manifold vacuum did the opposite which seem to defeat the purpose.
My 1977 Camaro (250 inline 6 automatic) has a dead spot / hesitation just off idle when I hit the gas pedal from stopped and when I hit the gas pedal from cruising.
I’ll hit the accelerator and it momentarily feels like it’s going to stall before the car springs into action and then it runs fine
Sometimes it causes the car to stall completely when I accelerate around a sharp corner or bend unless I coast it and accelerate gently.
Could the vacuum advance cause this ?
I’ve already had a carb rebuild , accelerator pump and new fuel pump.
Sounds more like a Carb problem. Check the vacuum advance canister to see if it's holding a vacuum and that it's plugged into a manifold vacuum port. Also check your base timing and make sure it's set between 10 and 12 degrees. Make sure the vacuum canister is unplugged when you check the timing.
The carb may have been rebuilt, but I'm wondering if it was properly adjusted - idle mixture settings and accelerator pump adjustments. What you are describing, the bog, sounds like a temporary lean fuel condition before the main jets are flowing enough gas for the engine to stabilize.
U forgot the No1 point . Vacuum advance occurs at light throttle steady state cruise ie between 27mph ---- 55mph . U set the xtra advance between these vacuum /road speed points .
If u still have a very basic distributor u may need xtra advance pending your setup so either manifold or ported setup might be better for you .
When u have standalone programmable timing idle timing and cruise advance can be what ever u want
So just for the record, the vacuum advance canister should be pulled in to the max at idle?
Yes and that's the point of the video, if you have low vacuum at idle or the canister is bad it may not pull in at all or only half way, big cams can cause this .
@@pyleup So we want to adjust that canister screw so that there's barely any advance timing while idling because if there is none then there will be a flat spot or delay after hitting throttle.
No that’s not it , you want Full vacuum advance timing at idle not part or none of it ,the moment you hit the throttle vacuum will drop and vacuum advance timing will drop out then you will be running on centrifugal advance of the distributor and what ever that timing curve is up to it’s max like 30 to 35 degrees at 3000 rpms. Vacuum advance is only for idle it will make it easier to start and idle better off idle throttle will be better street running. So you want to adjust it so you have full vacuum advance timing at idle.
what size allen? counter clockwise to be all in sooner?
Sorry, I don’t know the exact size of the Allen, but turning it clockwise reduce the amount of vacuum it takes to pull in sooner
Can the vaccume advance keep a older car from starting
It will make it harder to start but it won’t stop the car from starting itself it’ll just run rougher without the vacuum advance hooked up
I cant figure out how to tune/set up the advance on my 300 i6, I stuck all size allens in there and couldnt find anything to bite.
If you can,t adjust it a least you should be able to test it to see if it is working and at what vacuum it comes in at and test your vacuum on your 300 I6 . If it,s stock the only thing you need to worry about is if it works or not. The cannister can be bad. you need to pull a vacuum on it to see if it works.
Not ALL cans are adjustable! The only ones that I know of that ARE adjustable have the hex shaped nose like in the video.
Were you using an aftermarket distributor? I have a 300 i6 but am using an aftermarket HEI from Summit (SUM-850033). Same issue you had. The vacuum canister is supposedly adjustable but it seems I'm unable to get a bite on the allen key.
If I loosen advance is that less.tighten is more you did not mention
Every distributor will be different. If you test it with a vacuum tool you will know which way to turn it . But you have to be watching it with the distributor cap off, otherwise you will never know if you're doing it right or not. You can't just turn it cw or ccw without testing it. Some stock distributors can't be adjusted, but you can still verify that the advance is working by testing.
I have a '67 Cad deville w/429. Im having what feels like missing at acceleration 35 mph to 55 mph. Been told to replace dist but dont believe that is necessary? Im afraid its just a keep replacing parts to fix mindset. Im wondering about the vac advance? I got new part and when I pulled off old vac advance and found oil inside of it? Any idea why??
The vacuum advance canister may be leaking. The vacuum leak would pull in any oil from the surrounding area in the engine. If the vacuum advance canister doesn't hold a vacuum, it is bad.
The problem with having it hooked up to a manifold vacuum is that it pulls on the diaphragm all of the time thus shortening the life of the vacuum advance unit... If it was hooked to ported vacuum it would not pull 100% of the time.. just saying
Where has this video been hiding. How to adjust vacuum advance advice.
Hope you found it helpful
Where do I hook up the vacuum Guage to? Thx!
Intake manifold port or carb baseplate below thottle plate must be intake vacuum.
But make sure to hook the vacuum advance hose up to ported vacuum, not manifold vacuum when driving the car.
mistaken not oil but gasoline
Ford yes...GM no.