Dual Quad Carburetor Set Up

so i've been asked and asked and asked about this and i've always not been able to do it because i didn't have one available well i do now so what are we talking about today we're talking about dual quad setups so i very rarely get to do these anymore just simply because one the cost of it i mean that's a very expensive setup with the carburetor's intake linkage systems fuel it's just always been very very pricey the look is very cool and certainly it is still a a fun thing for street riders hot rodders muscle car guys it just looks cool it's hard not to argue that point but the problem with it is is the tuning side of things and getting these to run right and that's what typically happens is people will use them for a while they'll get frustrated with it by the amount of tuning that has to occur with it and they end up getting rid of them so today i'm going to give you a few tips and tricks that i've learned over the years on how to tune these how to set up the linkage properly and all the little things that go with it to try to make this thing run as best as we can now it's never going to be perfect it's a carburetor it doesn't matter if it's a single four barrel or if you're working with a six pack or a dual quad setup it doesn't really matter it's analog it's always going to need some adjustment it's always going to need a little bit of your time and attention it's just the way it is especially with today's ethanol fuel it just makes it a little bit more difficult so let's talk about this in order of the things that you really need to consider before you set this up and then as you are working through to get this thing running right and good on your street car now if you've watched any of my carburetor tuning videos in the past you i think you know what we're going to talk about right now and that's fuel system setup if you do not get the fuel system set up properly it really doesn't matter what the tuning side looks like it's going to fight you every step of the way so certainly we need to make sure that we have good filters within the system we have the pump that we need and a pressure regulator for whatever reason that pressure regulator is one of the most forgotten things in a fuel system and it's another adjustment point don't cheat yourself out of it you need it especially when you're talking about now multiple carburetors on one setup go ahead and make sure that you get a fuel pressure regulator because again it'll allow you to set the pressure that the carburetor sees and really help you get it dial in the tuning process now if you haven't seen my video on how to set up a muscle car fuel system that's a good one to take a quick look at it we'll go over this chart in depth and explain all the pieces and parts to it why they will all work together and why you should set up a system this way so i'll leave a link to that up above you can check that out after this video but getting the fuel system right is certainly the basis of everything we're going to do going forward and it really needs to be worked on first before you can jump into the cool stuff now before you get started on this thing one of the most critical pieces to this whole puzzle is ignition timing and i know we don't think of those two together adjusting carburetors and adjusting ignition together but really the two go hand in hand and you can't really adjust one well without doing the other so ignition timing is super super critical on this most engines on the factory and this one happens to be for a big block but small block big block type stuff you usually run a six to eight before top dead center of initial advance on a dual carb setup you're going to need to push that a lot more aggressively and i typically start these on the initial timing at around 14 to 16 degrees reason being it's a little bit more fuel there's a little bit more airflow it's just something that the engine is going to like a lot more timing in it so you can start to get the fuel and air that you're dumping through here burned the way it needs to be burned so always throw a little bit more timing at it now i know that's kind of a moving target that's just a a generalization depending on what engine you're working on but always give yourself a few more degrees of initial timing on the other side of it when you're all in on your timing it's the same thing if you're running around 30 32 of total timing in the thing you're probably going to need to push that up to 34.36 and again reason being more fuel and air you just need a little bit more time to burn it as it gets down into the cylinder so timing is critical i always set the timing first and then as you start to adjust the carburation on this thing it will help work together if you try to adjust the carburetors without touching the timing and want to go back to a second you're going to run into a lot of issues stumbling not idling right just go ahead and set the timing first while the engine is running and warm and then you can go ahead and and start working on carburetion and getting this dialed in now let's talk about linkage setups because i think there's some misunderstanding of what these types of linkages are and when you use them so on this intake manifold there is a progressive setup which means the primary carburetor starts to operate before the secondary carburetor and if you'll watch the linkage here as i pull it back accelerator pump will move and we're moving the throttle back before this block engages the secondary carburetor see how that works so what you're doing is you're adding fuel from one carburetor and then staging in the fuel from the second carburetor and airflow but a lot of people will get that confused and say well progressive must mean it just allows you to control the feeling a little bit better it's better for a street setup and while that's not totally incorrect it doesn't take into the main consideration of why you would use a progressive linkage so let's talk about the other one first and we'll talk about the intake manifold styles this is what we call a one-to-one or a tandem uh straight solid there's a lot of different names for this type of linkage and if you'll notice the bars are moved closer together where in this one they're moved farther apart and it allows that stop before it engages the primary or excuse me the secondary carburetor this one's locked so the carburetors operate together now when would you use a progressive and when would you use a one-to-one style well that largely depends on the type of intake manifold now on a on a dual plane style intake where the runners are all connected to a common plenum up top you can use a progressive style linkage because as you are feeding fuel from this carburetor in the rear it will still feed some fuel and air into these front cylinders what you're trying not to do is to lean these out and that's what happens if you run like a ton of ram style intake or a dedicated split intake where this carburetor only feeds the back four cylinders of the engine and this carburetor only feeds the front four in that case you have to use a one-to-one style linkage because if you don't it will starve the front cylinders or the rear cylinders depending on which one is your primary carburetor so it's a it's a big consideration it's all based on the intake manifold not by drivability or fuel economy or anything else now certainly a lot of people will tell you that they feel like that the one-to-one style gives them better throttle response it's better for drag racing and i don't disagree with that when you are feeding more fuel and air from both carburetors at the same time you are going to get a bigger surge of fuel and air obviously it gets down into the engine you create more horsepower so yes there is some little differences between the two but like i said the biggest biggest consideration is not anything else other than intake manifold once you determine what style of intake manifold you have then you can determine what type of linkage you use this is a dual plane that they're connected by a common plenum means that carburetor will feed the front and you can use a progressive style linkage now i like using progressive linkages they are certainly um very easy to adjust and kind of dial in where you want everything to to come in and timing as far as when the the secondary carburetor actuates but in all reality the one to one is my favorite style of linkage it just it's a little bit different on the tuning side but i like it because it just applies power a little bit quicker but again that is more situational in that style but it really depends on the intake manifold now you have the linkage out of the way we need to talk about how we're going to tune these carburetors now we're going to reference back to the tuning chart that edelbrock has given us to determine how to richen or how to lean these carburetors up now they are situational if you are using a one-to-one style linkage you're going to tune these carburetors differently than you are with a progressive in a progressive style i usually like to go a little fatter on the primary because it is feeding both sides and you do need a little bit more fuel and air to feed these front cylinders because of the way that the fuel and air has to route itself the rear four cylinders get a lot of air and a lot of fuel this one is a little bit more difficult and you do get into some situations where you could possibly lean out the fronts so i've always gone a little bit richer on the the primary carburetor and typically a little leaner on the secondary when you are doing a one-to-one then again it all depends on camshaft and compression ratio and all the little details of what the engine is so i'll usually go lean lean on both of these because you are feeding it a lot of fuel and air you can tend to lean this down a little bit again depends on the application we're talking more of a street application here i'm not talking drag racing it is totally different on how you fuel that type of application so we're just going to think of this in street terms so that's really again we're back to the linkage and that's it's such a key pivot point in what we're talking about here because they're all going to be fueled differently so now to the tuning chart if we're running a progressive setup and we want this one the the primary carburetor just a little bit richer then you just follow the tuning chart you follow it based on how you want it if you want a little bit more richer in the power mode then you know which steps you need to take if you want a little leaner in the cruise mode then you know which steps that you have to take and then you just reference over to the chart grab the rods and jets that you need make the changes that you need in the carburetor and then you're back to tuning and seeing how it worked out so i'm not going to get too in depth into the actual tuning of this setup here again everything's a little bit different but those are some general guidelines as far as how to tune depending on the linkage setup that you have i go tend to go usually a little richer on the on the primary carburetor and certainly a little leaner on the secondary it just all depends on the application though and everything's a little bit different now lastly i want to talk about just some other things that you're going to need certainly within the process you're going to need to have your your handbook that has the tuning charts in it it is a good reference and you're certainly going to reference that back when you're adjusting the carburetor side of things the other thing is you're going to need a couple of calibration kits and i know these are a little expensive so depending on how much tuning you're doing it may be a little bit more cost effective to try to piece together some other kits from friends or maybe you've got some rods and jets laying around that you can kind of reference back to but realistically buying the calibration kit for the part number carburetor is probably the easiest thing to do the last thing is very expensive and that's a afr gauge now i say very expensive because i tend to want to use in this type of setup a dual o2 sensor meaning there is an o2 sensor in the pri or this the driver side header and there's one in the passenger side header or just a little downstream of the collector now the reason why a dual o2 sensor works so well is because you can give get a better indication of how your tuning is going if you are a little lean on one side then you know that the adjustment that you made maybe isn't rich enough for what you're working with and that you need to kind of re-look at how much rod or jet that you're putting into it so i you can probably get away with a single o2 sensor and it really doesn't matter which side it goes on but it is certainly a good afr gauge for this type of setup is is invaluable now the old school guys will go well we didn't have afr gauge back in my day we just did it by seat of the pants and i don't disagree but the tools are available today use what you got let's talk about size of carburetor because really when we talk about how to get the right size carburetor on any muscle car or any carbureted application certainly getting it very close to the size that you need is very very important when you're talking about a 2-4 setup it's even more important but not for the reasons that you may be thinking intake manifolds really are the key to how a carburetor fuels a system how the the plenums are divided what the runner length are what the signal is coming up from the intake manifold to tell the booster and the main metering circuit how much fuel to give the engine so if you get the sizing right on on it this good 2-4 setup you're going to have a much easier time tuning it now this is for an oval port big block chevy these are 500 cfm edelbrock carburetors now a lot of folks will go that's too small you probably should at least run the the 650 if you're gonna run the avs2 and i don't disagree the 650 might be a little bit better if this had a little bit bigger camshaft a little bit more compression where it could operate at that range but in this instance it was a very mild setup and the 500s worked even better for it now these are also the avs2 carburetor so it has the annular boosters which certainly make it a lot easier i do believe on tuning because i believe the atomization of the fuel and air is a little bit better and i think it just makes it a bit easier especially when you're talking about a progressive style linkage like this one is and how it fuels from the primary carburetor into the front four cylinders so anything you can do to take change that liquid into more of an atomized mixture helps to flow that fuel and air into the primary side of the or the front four cylinders of the engine now is there a common formula you can follow like we do on a single force setup like we talked about in how to choose the right size carburetor video and i think the answer to that is no a lot of this i think is really dependent on very much seat of the pants or experience really is what it boils down to where i knew i could run 500s on this setup and still be able to tune it and do a good job of getting the right amount of fuel and air to the engine now this setup has had 650s on it before and it did run fine but it was a camshaft change to a smaller cam that dictated that we go to a smaller carburetor and i felt like they could be tuned just fine and they were but again it's i think it's just more dependent on where we get very very hyper sensitive to all the other little details of driving style and what the intake manifold you're using what the camshaft is all the little engine details those are become even more hyper sensitive to what size carburetors you're going to choose now certainly on a race application it becomes a lot easier because carburetor size is so much easier at that point because you're typically almost always on a one-to-one style linkage and you can't you can't overfuel them that's for sure but the the mistakes become a little bit less at that point as long as you're not down around you know 10 to 1 on an afr where you're really really over fueling it it's it's a little more forgiving on the racing side of it the street side it can be as forgiving but it's just going to be stinky and foul plugs a lot and you know stink up your garage and all the things that over carbureted setups do so i'd love to be able to give you a nice simple formula of really how to do it but honestly i think in that aspect if you're going to run a 2-4 setup whether it's a tunnel ram or a low-rise style intake you're better off just contacting a manufacturer carburetor or intake manifold manufacturer and telling them about your setup and let them suggest the right cfm carburetor for your application so that's really the basics of it you know it i've said this a hundred times on this channel everything is situational there's not one camshaft that's better for a big block chevy there's not one carburetor size that fits everything that's best for everything there's certainly not one brand of carburetor manifold crankshaft rotating assembly cylinder head that's the best for the best everything is situational and certainly in this application it takes everything to another level because certainly you want to get things as dialed in as possible and every little change that you make is hypersensitive when you're talking about two different carburetors now on a single manifold thingy feeding a single engine so it's super critical to get all the little details right when we talk about fuel system i know we've beat that to like a dead horse but that is absolutely a critical piece to the whole puzzle ignition timing if you don't get the timing right and start to operate it based on what you're working with none of the tuning is going to be very easy if you use the wrong linkage setup and you're a little lean on those front four cylinders it doesn't matter what other timing or whatever adjustments you make in the carburetor are it's just not going to you'll always continue to fight it and then you'll just assume well the the this the carburetor is your junk or a dual setup is a is junk it's too difficult to tune it's difficult to tune but it's not impossible and you have to follow the steps in the process and if you do that these can be very very fun to drive they certainly look very cool when you pop open the hood or have them sticking through the hood depending on what you're working on so yeah don't don't get frustrated with it but just understand that every little problem is compounded by two when you're talking about a dual quad setup so just be patient with it you're gonna need a lot of that for sure some other tools to help you out with the dfr gauge and certainly with a good calibration kit and everything should work out just fine so hopefully some of those tips will help you get your setup dialed in and again if you've got any questions don't hesitate please leave them down below i'll try to answer them the best i can and hopefully you'll have some good long service life and a lot of fun out of your 2-4 setup we will catch you guys on the next one see ya

Channel: Muscle Car Solutions

Views: 35,120

Keywords: dual quads, dual quad tuning, big block dual quad set up, chevy, edelbrock, edelbrock carburetor, holley, holley carburetor, low rise dual quad, edelbrock dual quad setup, edelbrock 2 four set up, edelbrock dual-quad manifold, edelbrock RPM air gap, performer RPM, RPM Air-Gap Dual-Quad, Edelbrock RPM, Dual-Quad Kit, edelbrock 7520, edelbrock AVS2, edelbrock endurashine, edelbrock endurashine carburetor, tunnel ram, big block chevy, big block tunnel ram, big block dual quad

Id: OYylACoMd4M

Length: 19min 50sec (1190 seconds)

Published: Sun Jul 25 2021