Fine Tuning a 360 Magnum with a Brawler "Double Pumper"

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jmanhoff said:
Alright so forgive me for asking a million questions but I’m trying to see if I’m truly grasping the fuel circuits.

So the idle circuit contains the IFR and idle air bleed, and it controls the idle circuit and the transfer circuit. Low speed, low throttle situations are running on this circuit.

The main circuit includes the main air bleed, emulsions and main jets and isn’t really doing anything until 2500ish rpm when the Venturi is strong enough to pull the fuel through the boosters.

The emulsion ports are mixing air and fuel through the PMJ and air bleed and sending it through the booster, and any ports above the bowl level are mixing air, below the bowl are mixing fuel. So blocking off the middle port which is right at the fuel level will essentially make it a 1:1 mix of air and fuel (I know it’s not literally what’s happening but 1 hole is fuel, one is air so that’s my idea for the 1:1 ratio.)

Is that the correct or at least right track logic?

I’m also planning on just buying some brass set screws most likely, I’m assuming brass is the universally accepted material. Should I go with 1/4 long or 1/8 long?
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It’s absolutely refreshing to hear that you took the excellent advice given by many here to learn how the circuits of a carb work and interact with each other. Good job, keep reading because you’re learning and it will pay off in the long run. You are a little off in the time line of how the air and fuel mix through the main circuit with regards to emulsion and air bleeds and such, but if you look for the info it’s out there. Well done!!
 
TT5.9mag said:
It’s absolutely refreshing to hear that you took the excellent advice given by many here to learn how the circuits of a carb work and interact with each other. Good job, keep reading because you’re learning and it will pay off in the long run. You are a little off in the time line of how the air and fuel mix through the main circuit with regards to emulsion and air bleeds and such, but if you look for the info it’s out there. Well done!!
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The big thing I’ve been looking for is like diagrams and drawings of the circuits and then how they work, though I’m sure all of those manuals and stuff that have been linked have some sort of diagrams for the circuits. That’s how I process things better is with visuals.

I can read and read and probably eventually get it but my mind sucks at visualizing things that I’m reading, but with an explanation and a diagram, I’m golden lol
 
Search the posts @Mattax has put in this thread, as well as many others. If you go to the search function and just put his name in and search for carb tuning, you’ll find lots and lots of diagrams. Also the naca paper that @Newbomb Turk referenced has plenty of drawings with lots of great information. Just google search naca 49. It’s called “metering characteristics of carburetors” and on nasa.gov it’s a free download.
 
TT5.9mag said:
Search the posts @Mattax has put in this thread, as well as many others. If you go to the search function and just put his name in and search for carb tuning, you’ll find lots and lots of diagrams. Also the naca paper that @Newbomb Turk referenced has plenty of drawings with lots of great information. Just google search naca 49. It’s called “metering characteristics of carburetors” and on nasa.gov it’s a free download.
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I think I gotta do that on the computer, seems like the mobile site doesn’t have as many features lol
 

So another quick question, I've seen two different things but are the 6-32 restrictors UNC? I have found 10-32 UNF but no 6-32UNF, only UNC. I've also found a set of blanks that are 6-32UNF but could that just be a typo?
 
The reason they use unf or unc is when you have multiple thread pitches for the same size fastener.
IE 10-32 would be UNF, fine thread.
10-24 would be UNC, coarse thread.
 
TT5.9mag said:
The reason they use unf or unc is when you have multiple thread pitches for the same size fastener.
IE 10-32 would be UNF, fine thread.
10-24 would be UNC, coarse thread.
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Okay that makes a lot more sense.

Update for ya gents, I just ordered some blanks and .028IFRs. Going to tweak one thing at a time. Well I guess two in this case. Blocking the middle emulsion holes, and removing the top .031 IFR and replacing it with a .028 on the bottom as Turk recommended.

I cant get any brass set screws locally and soonest I can ship any is next week, winter storm surely not helping, so t-slot restrictors will come later.

I do have a question that may have been answered but I'm half asleep and wrapping up my thoughts: is the pump shot an entirely independent circuit? As in the changes I'm making won't affect the stumble if the pump shot was an issue?
 
jmanhoff said:
Okay that makes a lot more sense.

Update for ya gents, I just ordered some blanks and .028IFRs. Going to tweak one thing at a time. Well I guess two in this case. Blocking the middle emulsion holes, and removing the top .031 IFR and replacing it with a .028 on the bottom as Turk recommended.

I cant get any brass set screws locally and soonest I can ship any is next week, winter storm surely not helping, so t-slot restrictors will come later.

I do have a question that may have been answered but I'm half asleep and wrapping up my thoughts: is the pump shot an entirely independent circuit? As in the changes I'm making won't affect the stumble if the pump shot was an issue?
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Yes it is its own circuit. You probably want to try a bigger shooter for what it's worth before drilling ****. I'm saying this because we're talking about a stock cam engine with a ton of vacuum...
 
jmanhoff said:
Okay that makes a lot more sense.

Update for ya gents, I just ordered some blanks and .028IFRs. Going to tweak one thing at a time. Well I guess two in this case. Blocking the middle emulsion holes, and removing the top .031 IFR and replacing it with a .028 on the bottom as Turk recommended.

I cant get any brass set screws locally and soonest I can ship any is next week, winter storm surely not helping, so t-slot restrictors will come later.

I do have a question that may have been answered but I'm half asleep and wrapping up my thoughts: is the pump shot an entirely independent circuit? As in the changes I'm making won't affect the stumble if the pump shot was an issue?
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What size pump shooter do you have?

Also, one more time for me because I’m old, clue me in again where the stumble is and how much throttle are you into when it happens.

Just an FYI. Having an extra emulsion hole open, or more than you need is a better way to say it or using too big of emulsion holes will cause what is called “slugging”.

You can see it on an A/F ratio graph. You will see a saw tooth pattern where it goes rich and lean because it’s getting a big slug of air. Then a big slug of fuel.

At any rate, slugging is real. Emulsion is to correct the fuel curve, not to emulsify fuel.
 
Newbomb Turk said:
What size pump shooter do you have?

Also, one more time for me because I’m old, clue me in again where the stumble is and how much throttle are you into when it happens.

Just an FYI. Having an extra emulsion hole open, or more than you need is a better way to say it or using too big of emulsion holes will cause what is called “slugging”.

You can see it on an A/F ratio graph. You will see a saw tooth pattern where it goes rich and lean because it’s getting a big slug of air. Then a big slug of fuel.

At any rate, slugging is real. Emulsion is to correct the fuel curve, not to emulsify fuel.
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Right now I have a 35 shooter, went up from a 31 that came stock. Still have the stock white cam.

The stumble happens when I'm off the throttle and quickly get into it. For the most part, if I'm already down on the throttle a tiny bit and I quickly press it, it revs up with a very slight hesitation. If I'm fully off the throttle and I smash the gas it cuts out and then goes.

Doing Dominos, I can get a lot of different scenarios knocked out in a short span of time which I guess is useful to a point lol. If I ease into the throttle it doesn't hiccup at all, it's just anytime I remotely quickly get into the gas.

I think it's difficult to get that pump shot figured out because it's a relatively light truck with a really short first gear, and a bunch of torque so it gets moving quickly. If I was to try to fully open the primaries and try to get moving fast, I guess the best way to describe what the engine sounds like is puh-WAHHHH *shift* puh-WAHHHHH. (The "puh" being a cutout lol, it throws you forward into the wheel and the nose drops, then the other circuits catch up and then it throws you backward into the seat)
 
jmanhoff said:
Right now I have a 35 shooter, went up from a 31 that came stock. Still have the stock white cam.

The stumble happens when I'm off the throttle and quickly get into it. For the most part, if I'm already down on the throttle a tiny bit and I quickly press it, it revs up with a very slight hesitation. If I'm fully off the throttle and I smash the gas it cuts out and then goes.

Doing Dominos, I can get a lot of different scenarios knocked out in a short span of time which I guess is useful to a point lol. If I ease into the throttle it doesn't hiccup at all, it's just anytime I remotely quickly get into the gas.

I think it's difficult to get that pump shot figured out because it's a relatively light truck with a really short first gear, and a bunch of torque so it gets moving quickly. If I was to try to fully open the primaries and try to get moving fast, I guess the best way to describe what the engine sounds like is puh-WAHHHH *shift* puh-WAHHHHH. (The "puh" being a cutout lol, it throws you forward into the wheel and the nose drops, then the other circuits catch up and then it throws you backward into the seat)
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I don’t use 35’s on anything that isn’t a tunnel ram or a carb that’s far too big and poorly tuned.

I’m still trying to figure out if it’s going lean on tip in or if it’s fat. I’m leaning towards it’s going rich but I’m not sold on it yet. I’m still thinking.

One issue is if you are cruising and you just lean into the throttle and it stumbles is different from cruising along and sticking your foot through the floorboards and it stumbles.

The former will never get cleaned up from pump shot. You can test this by holding the engine at cruise rpm and then just ease into the throttle and you’ll see the fuel just pee out of the squirter.

The less aggressive the pump cam and/or bigger nozzle will make it worse.

I’m talking about with the car parked and you running the throttle by hand to see that.

The other thing is main air bleed size. The main air bleed controls when the booster starts. A bigger main air bleed starts the booster sooner so it will be richer sooner. There is overlap between the T slots and the mains. Start the booster too early and they get rich.
 
So the right tap I would need is one for a through hole right? I bought a kit that said it was good for through and blind holes though it has a point, every other blind tap I’ve seen is flat at the tip, but I’d imagine if I’m drilling and tapping passages they would be through holes
 
Newbomb Turk said:
I don’t use 35’s on anything that isn’t a tunnel ram or a carb that’s far too big and poorly tuned.

I’m still trying to figure out if it’s going lean on tip in or if it’s fat. I’m leaning towards it’s going rich but I’m not sold on it yet. I’m still thinking.

One issue is if you are cruising and you just lean into the throttle and it stumbles is different from cruising along and sticking your foot through the floorboards and it stumbles.

The former will never get cleaned up from pump shot. You can test this by holding the engine at cruise rpm and then just ease into the throttle and you’ll see the fuel just pee out of the squirter.

The less aggressive the pump cam and/or bigger nozzle will make it worse.

I’m talking about with the car parked and you running the throttle by hand to see that.

The other thing is main air bleed size. The main air bleed controls when the booster starts. A bigger main air bleed starts the booster sooner so it will be richer sooner. There is overlap between the T slots and the mains. Start the booster too early and they get rich.
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Would a video of what it sounds like be helpful? I have one when I was getting a video of the new exhaust where you hear the exhaust cutting out, but I can also take one of the carb with the throttle movement
 
jmanhoff said:
Would a video of what it sounds like be helpful? I have one when I was getting a video of the new exhaust where you hear the exhaust cutting out, but I can also take one of the carb with the throttle movement
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Yes.

Also I forgot to mention I am using spiral flute taps to do all my carb work any more.

They do a way better job than a straight flute tap.
 
Newbomb Turk said:
Yes.

Also I forgot to mention I am using spiral flute taps to do all my carb work any more.

They do a way better job than a straight flute tap.
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The current taps I have aren’t spiral tap but they are through taps so I guess I can start with those and see how it goes. I’m not going to be tapping a million holes anytime soon so I think I can suffice for now.

Here is a video of the exhaust, I would take a video of the carb side but it’s currently snowing and 25 degrees so it would take a year for the engine to warm up lol

 
I use bottoming taps on just about everything. They’re a little harder to start but that’s the only real downside. Spiral flute taps are fancy. Too good for me and the girls I date.
:lol:
 
TT5.9mag said:
I use bottoming taps on just about everything. They’re a little harder to start but that’s the only real downside. Spiral flute taps are fancy. Too good for me and the girls I date.
:lol:
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Me too but I just don’t tell my wife about the taps or the girls I date lol
 
jmanhoff said:
The current taps I have aren’t spiral tap but they are through taps so I guess I can start with those and see how it goes. I’m not going to be tapping a million holes anytime soon so I think I can suffice for now.

Here is a video of the exhaust, I would take a video of the carb side but it’s currently snowing and 25 degrees so it would take a year for the engine to warm up lol

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Did you measure the main air bleed yet?
 
Do I have this backward or the right idea?

Bigger main air bleed makes the boosters come in sooner but it’s richer down low, leaner up high.

Smaller main makes booster come in later and leaner, richer up high?
 
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