Ported vs. Manifold Vaccum Advance! | Were To Hook It Up And Why | How Are They Different?

junkyard junkyard junkyard you know me and junkyard have been having this you know discussion for you know literal months I think finally it boiled down to well let's make a couple videos right and I you know I was preparing myself you know to really have an actual battle on my hands right I thought he was gonna break out like you know schematics and like you know EV talk and all this and that but you made it way too easy bud let me show you how it's really done all right [Music] so if you're not yet seeing the junkyard Necromancer video none of this is going to make any sense to you so probably go watch that first but if you've watched it you'll notice you know we're gonna just go through it step by step here right a lean mixture Burns slower a rich mixture Burns faster right on his whiteboard there right this I mean this is you know something his core belief that he's you know relying all this information on I guess okay well is that true though well you know okay let's consult Google hi okay yeah no it's it's totally true look at that oh wait oh Motor Trend says it's not true so which is it well you get two conflicting statements from two conflicting sources I guess you know really doesn't matter that much because we're not really talking about lean mixture versus Rich mixture here we're talking about cylinder fill now lean and Rich mixtures you know play a role but not nearly as much as cylinder fill and cylinder fill is really why we have advanced in the first place and unlike junkyard I'm not you know the pseudo scientist person I'm a card guy so you know what I'll I'll just do my demonstration on this Crager box here I wonder Phil is simply how much stuff is in the cylinder now this is not air fuel ratio this air fuel ratio that air fuel ratio exactly the same but you got to remember the cylinder is a vacuum this is not constantly full of air that we're just dumping fuel into air and fuel have to come into it well I guess it technically be on this side but well no it doesn't all right air and fuel have to come into it it doesn't already have air in it so cylinder fill is simply how much air and fuel occupies the volume of the cylinder the less you have the longer it takes because each one of these particles has to jump to the next particle and that takes time in order to fully combust the mixture you have a dense cylinder fill well then it's a chain reaction just you know it all combusts rapidly that is a fast burn this is a Slow Burn so when would these two events occur when would you have a lower density cylinder fill when would you have a higher density cylinder fill well I mean it just stands to reason using Common Sense let's go look at the engine the only way for air and fuel to get inside the engine is through your throttle body whatever type it is and at idle all the butterflies are usually pretty much closed so you could deduce that at idle and on low RPMs when you're not opening the throttle very much you're probably having a lower amount of cylinder fill in your you know engine because simply the air and fuel can't all make it in there depending on what camshaft you're running how big it is will determine where it really makes power that has to do with cylinder fill too oh your heads you know how much your heads flow if there's small ports of big large ports like a Cleveland head well the velocity going through the whole intake system low velocity while you're not getting a whole lot of stuff in there you have high velocity you're getting some stuff in there unless the port's too small High Velocity through a small Port you're still not getting much in there but you know what low velocity through a big Port you might get some in there so it really it all boils down to what kind of engine you have and well you know that boils down to how much ignition timing you need because the lowest density cylinder charge you need to ignite the charge sooner well if this takes a longer time to fully burn because it has to jump from molecule to molecule and there's a big gap in between them all because it's a low density charge you gotta ignite this mixture ahead of time as the Piston's coming up you need this mixture to start burning so by the time it gets to top dead center and just a little bit after it can finally push the Piston down you want Peak cylinder pressures to happen right as the Piston is starting to come down anything before that you're going to be fighting the piston on the way up anything after that well then you're missing it the Piston's already traveled down and the expanding gases cannot expand hard enough to keep pushing it down what happens when you floor that yeah what happens when you fully open the butterflies well you are filling the cylinder more you're getting a denser cylinder charge than when the butterflies were closed so you don't need quite as much not quite as much would be you know the typical timing curve you you know usually have you know 30 something total timing right that's probably all it needs but under light Cruise or at idle or whatever right on not high density feeling situations where you're not fully into the throttle you need more timing I mean you could run up to 40 50 possibly even 60 degrees of timing depending on the combination and it's totally fine under light cruising so that's pretty much what junkyard covered in his video and then he just kind of claims that well manifold vacuum is just the way to go so do it and you'll be happy it doesn't really explain too much further than that well that's leaving a lot of meat on the table there I how do you even know how much time the engine wants that theory and everything is great and fine but how do you actually apply it right I mean how do I know how much the cylinder is getting filled there's no you know there's no gra there's nothing on the outside of the engine that's going to tell me how good it's doing that's what the gauge is for the vacuum gauge vacuum gauge will tell you exactly how good your engine's doing how much cylinder fill it has whether it's hard or not the vacuum gauge is the lifeblood The crucial you know piece of information you need for these old-timey engines right oh even new engines but you know the vacuum has been replaced by Electronics with new stuff and how do we utilize the vacuum gauge what are we looking for I mean what what what's it going to tell me where do I plug it in right okay well I can show you exactly how this thing works and explain to you the true differences between manifold imported vacuum just so we understand what we're talking about now this is hooked to manifold vacuum at the moment and I'll explain that in a second but as you can see it has a steady cup to vacuum now it's so deported back here and as you can see there's no vacuum at idle well it's because ported vacuum is above the throttle Blades of the carburetor and manifold vacuum is below it since we're taking our vacuum reading from up here the throttle blades are closed therefore there's no vacuum at idle and if we're taking the vacuum reading from down below well now you're getting all the suction from the Pistons and everything so you have constant vacuum manifold versus ported it's a difference at idle you know without the butterflies open what happens when you're you know putting the gas on taking it off you're matting it wide open throttle you're on deceleration what's the difference then they're still on the ported there's nothing but let me come over here [Music] so when you open the throttle with ported vacuum you actually gain vacuum you can see the needle jumps up and it'll jump up according to how much throttle you give it how rapidly you give it you know that kind of thing but just when it's hooked to ported vacuum when you apply gas it will add vacuum well let's try manifold now we got to hook back to manifolds what happens when I mess with the carburetor [Music] oh [Music] as you can see hooked a manifold vacuum it does the exact opposite it will take away timing as soon as you do the throttle and how much throttle you give it again determines how much it takes away so when you want to hammer the thing it takes all your timing away from you that's the way it works now you know the differences between Port of vacuum manifold vacuum now let's talk about vacuum itself how do you gain more vacuum how do you lose vacuum and how does vacuum tell you what's happening inside your cylinders well let me show you now our mission is to use all that's in this side this cylinder everything that we can cram in we want to fully burn it in order to push this piston down but if we don't fully burn it and we have an incomplete burn some stuff's going to be left in here and if there's some stuff left in here we can fit Less in there if we can fit Less in there then we're going to have a drop in a vacuum because the more suction there is this is completely empty that's going to bring more in you're bringing more in your vacuum is up you're bringing Less in your vacuum is down now that's when you're at you know idle or maybe part throttle when the throttle blades are not all the way open when the throttle blades are all the way open if you have a vacuum a significant vacuum a wide open throttle then that means there's a restriction like too small of a carburetor maybe too small of an intake but otherwise an idling like Cruise tells you exactly what you need to know are you using the fuel to its fullest capability that you're fitting inside that cylinder well the way we you know look for that you tune to the highest vacuum we're starting off here and we're wanting to tune our carburetor and we come over here we push onto him and we start messing around [Music] I'm adding fuel and as a result our vacuum has dropped because we're not using the fuel to its fullest capabilities so we lean the mixture back out [Music] we gain vacuum because now we're better using the fuel we're putting in there as a result of higher vacuum usually it equals out to higher RPMs the two are kind of interconnected that way you get higher RPMs because it's able to burn the mixture more completely less faster thus rotating the engine faster and you tune to the highest vacuum what you're doing is you're putting the engine at optimal it its optimal capability but what you're also doing is you're putting it on knife edge any little disturbance you know a little slightly bad fuel you know a little bit bad you know climate you know it gets hot or something like that and you're too cold any kind of disturbance you don't really have margin of error okay that's why if you're tuning to the highest vacuum back it off just a little bit just give it just a nudge more fuel than optimal all that's doing is assuring that even if things kind of get unstable a little bit you're still safe you can use that exact same method on your timing you can tune to the highest vacuum with your timing also and again just once you reach it just it just a little bit that way you're still a little bit safe but that brings us to our vacuum advance and our timing well what's it want well the engine wants whatever it tells you it wants it doesn't give a rat's ass what you think it wants the engine will tell you exactly what it wants by increasing the vacuum and increasing the RPM so all you do is you come over here you turn it on right at idle or at Cruise or whatever increase the timing until it stops building vacuum if you increase the timing and it builds vacuum builds vacuum and it stops you give it a little more it doesn't move that means you've used everything you can inside the combustion chamber it will be a period in time a slim one where the amount of timing you have won't really change anything very much because you've already fully combusted this mixture starting it sooner won't combust it anymore if you've already used it all there won't be anything left to you know use up so doing it a little bit more doesn't help you it doesn't raise the RPM which signifies better burning it doesn't rain raid the raised vacuum which also signifies complete burning then it's not doing any good to have that extra timing all that's doing is making it more prone to detonation or you know misfiring and stuff like that and you want to tune to just almost optimal you want to leave just a little bit room because this is a dynamic environment right we're tuning a static you know thing for a dynamic environment you know everything changes you want to build in margins of error into your tune now this is just a little vacuum pump and I got a hook to the man or the vacuum advance so clearly we're adding timing and it likes it [Music] hasn't changed our little demonstration however much Advance we had when the vacuum stopped building that would be optimal you back it off a few degrees in this demonstration we just simply maxed out the capabilities of a vacuum pod dissolve so this you want to truly just be doing it with the actual distributor itself and then use this for fine adjustments like out cruising and Andy Wood uni Motorsports garage and David vizard you know the legend himself have a video all about how to do that just showing you that that's kind of the way to do it look at their video for a more detail-oriented explanation I don't want to steal it from them go watch their stuff now that we've completely dissected vacuum in its entirety right now comes down to the ultimate question ported versus manifold which one to use for your vacuum advance distributor well very simple manifold vacuum and ported vacuum are only different once you hit the throttle when you introduce more air into the system once it becomes a steady state once you have opened this as much as you're opening it you know very small you know increments just cruising down the road the top side and the bottom side equalize they become exactly the same so manifold versus ported well at a light Cruise doesn't matter it's the exact same regardless the only difference is that Idol there's no vacuum and when you crack the throttle open manifold will take vacuum away where ported will add vacuum so which do you want question's not really about manifold versus boarded vacuum the question is when you hit the gas do you want more timing or less timing on the launch or when you're accelerating because the mechanical the mechanical timing we can adjust to suit our needs we can set initial timing to 22 degrees if we want to we can set it to 36 degrees if we want to and just completely lock out the distributor we can inset our mechanical to whatever we want it's just the vacuum that we cannot set to what we want it does its own thing based on throttle response mechanical we have full control over so if I want 22 degrees of initial timing just throw in the number out there as an example not necessarily that you do or don't 22 degrees initial advance I can either set this initial timing mechanical timing to let's say eight degrees and just use manifold vacuum to bring me up the extra you know 12 degrees 14 degrees and when I hit the gas when I really want to get going all my vacuum drops and I go back down to eight degrees initial timing as I'm trying to get the thing to motor away or I can set the initial to 22 mechanical not have any vacuum and when I hit it it will actually give me more timing so what do you think you want to leave the starting line on eight degrees initial timing or do you want to leave the starting line at 22. even if you have your mechanical Advance coming in quick right you know let's say you got it coming in at you know 16 18 you know 100 RPM hey you got the thing coming in quick it still takes more time to go all the way from eight up to the 36 34 32 you know whatever number you have as you told the timing right off the hit when it matters the most manifold timing will completely take away all of your timing take away all of your grunt off the line and mechanical timing if you just do mechanical and use ported you can have all your initial timing and it'll actually give you a little bit more if when you need it like you've seen when we flip the throttle it spiked and then it came right back down that initial hit it gives you more timing right when you need it the most right then you have the timing you need to get off the line if you've ever bumped up initial timing to try to get more yeah if you've never experienced it go ahead try it if you have you know 10 degrees in there right now bring it up to 14 and just give it a shot you will feel the difference I mean that's not debatable there you go you make your own decisions I'm not telling the engine what it wants the engine tells me what it wants but how it reacts so that's all I got for this episode I'll catch you next time

Channel: New Guys Garage

Views: 18,850

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Id: wfzXmBKkxVQ

Length: 21min 7sec (1267 seconds)

Published: Sun Jul 02 2023