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

[Mattax]

Lol I’m also just a really stubborn traditionalist because my dad grew up with mopars and holleys so I’m kind of just following the same road.

To be frank you're throwing darts blindly. Pin the tail on the donkey without seeing the donkey.
The first thing you need to do to seperate wheat from chaff is know the difference.

Go read the booklets from Chrysler on carburetor fundementals.
Its free at available at your electronic fingertips. Urich and Fisher will have to be found or ordered from ebay or 'zon so you won't get it for a week. Its not that its a great book, but the explainations in the front are some of the best I've seen. Written by guys who were engineers as opposed to enthusiatic magazine writers.

If the idle isn't right, then all of the adjustments you make from off idle on will not be right, and will have to get readjusted if you care to really tune it in. There's exception but you're driving a street truck, not a dedicated drag race car - and even there can't get away with stuff that people used to in amateur races.

really basic stuff has been skipped. timing at ______, fuel level, transfer slot exposure, idle mix adjustment, choke pull off; never mind number of e-holes and so forth.

You've been given lots of information because you keep asking questions and making assumptions. I'm not typing any more. Its pretty much all there in the various links and searches. You'll have to assemble it.

One more to help your understanding

Purpose of Timing

Mechanical or Centrifical Advance:
Compensates for the reduced amount of time (miliseconds) available for the burn as rpm increases. But because increased engine efficiency decreases burn time as rpms climb, the rate of advance is not always propertional to rpm. A 'low performance' 318 usually has good lower rpm efficiency, but does not gain as much efficiency with increasing rpm. A 'high performance engine' is usually the opossite.

Purpose of Vacuum Advance

pretty much right from Chrysler's booklets for their techs.

 

[Newbomb Turk]

So obviously in order to get all the actual nozzle and jet sizes I'd need a pin gauge set. Would a 0.011-0.060 set be suffice? Theres really two that I can see, the M0 which seems to be as mentioned, then a M1 which is 0.061-.250. Or could I use the numbers stamped on any of the parts that have holes larger than 0.060"? I'd imagine since they setup the carbs to flow XYZ they would just use a different part and not drill it in the factory so the part numbers should be accurate?

I'd get the M0 set and then for the bigger stuff like idle air bleeds and T slot restrictors you can use drill bits to check sizes.

You'll need the drill bits anyway to make up the bleeds/jets.

 

[Newbomb Turk]

So I've been reading the threads that were posted earlier and came across this post and wanted to verify that I was understanding this correctly in terms of the PV.

So theoretically, say I go down to the 64 PMJs, and run a 10.5PV, or even a 12.5PV if I ran the alcohol ones? If the motor runs fine at light throttle (T-slot to booster) on the 64s and when I need a little more power and I put my foot down, would the sooner opening PV help with the lean surging or do I need to just stick with the 66s?

Basically, the 64s, at least how the carb sits right now without messing with anything else internally, are the smallest jets I can run before I'd imagine I'd see the plugs too lean. (I believe I posted the plugs with 66s in this forum way back when, and someone said I could probably go a touch leaner), so would a numerically higher PV potentially fill this lack of fuel?

That's pretty close. You can tune the power valve circuit two ways. One is when it opens relative to engine load (vacuum) and the other is by the size of the hole in the power valve fuel feed.

If you remove the power valve you'll see two holes. If your carb isn't already threaded you can drill and tap that feed to 8-32 or maybe 10-32 I'll have to look at what size I use there. I know it's 10-32 for the T slot restrictors so think it's 8-32 for the power valve.

Anyway, putting brass in those holes (if there isn't already brass in there, depends on the carb) allows you to change how much fuel you add to the main circuit when the power valve opens.

A bigger number on the power valve opens it sooner and a lower number opens it later.

A bigger or smaller jet behind the power valve makes it richer or leaner.

In your example above you might open the PV sooner if it needs more fuel sooner or if you figure out if its opening at the correct time you change the jet behind the power valve to adjust for that.

It's called power valve channel restrictors. I just hate typing all that out multiple times.

 

[jmanhoff]

Alright. I think I’m done blabbing too and I’ll start actually looking at the important stuff. Time to stop being lazy lol, my whole reason for essentially ignoring what the real problem is and looking for a bandaid is because I didn’t feel like tearing the carb apart and being nitpicky.

I have the pin gauge kit in my amazon cart and will hopefully be able to order it soon just depends how much my exhaust ends up costing me.

I have work at 2 today so don’t have a lot of time to mess with things but for a start what I’ll do in the next hour or so is pull the metering blocks off and snap some pictures so we can see what holes are plugged, where what bleeds/jets are, etc. I’ll also pull the carb off and see where the t-slot currently is (also lets me get a count for how many turns from fully out the idle screw needs to make the t slot a square)

 

[jmanhoff]

Got some pictures will post them in just a minute but I just stopped at work after setting the t slot to be a square, and timing is still the same at about 18. My idle is super high, was at 1200 when I was driving and it dieseled like crazy when I shut it off. Should I back off the timing slightly? If I close the idle it won’t show any t slot anymore, and it’s backed off basically all the way. To show the t slot it’s half a turn once the screw contacts the arm

 

[TT5.9mag]

Got some pictures will post them in just a minute but I just stopped at work after setting the t slot to be a square, and timing is still the same at about 18. My idle is super high, was at 1200 when I was driving and it dieseled like crazy when I shut it off. Should I back off the timing slightly? If I close the idle it won’t show any t slot anymore, and it’s backed off basically all the way. To show the t slot it’s half a turn once the screw contacts the arm

How “closed” are the secondary butterflies? If they’re open at all I’d close them to lower the idle. Then I’d retard timing. You can move the primary blades around a little but you want to keep the T slots fairly square.
Edited to add;
The secondary idle stop screw is almost always buried under the baseplate and not easy to get to. But it is there.

 

[jmanhoff]

How “closed” are the secondary butterflies? If they’re open at all I’d close them to lower the idle. Then I’d retard timing. You can move the primary blades around a little but you want to keep the T slots fairly square.

They’re closed completely if I see correctly. I’ll post pictures in a second you can see both sides

 

[jmanhoff]

This is the primary metering block.

Secondary block.

Current T-slot exposure (half turn out)

Secondary side.

 

[Newbomb Turk]

View attachment 1716363373View attachment 1716363374View attachment 1716363375
This is the primary metering block.

View attachment 1716363376
View attachment 1716363377
View attachment 1716363378

Secondary block.

View attachment 1716363379
Current T-slot exposure (half turn out)

View attachment 1716363380
Secondary side.

I can’t see well enough in the pictures but if the T slots are square on both sides secondaries are open too far.

Or there’s an air leak because square T slots isn’t much opening.

Figure that out first.

Second, you will NOT go to hell and burn forever if your T slots aren’t square. I don’t know when it became the do all, be all, end all but it’s not.

Start with them square and tune it from there. If you get them open too far you’ll figure that out.

Second, stop listening to the internet about some spectacularly high initial timing. That’s bullshit.

I forget if you posted your idle vacuum but if you have 20 at a cruise you probably have enough at idle that you don’t need some mega high initial.

You need that when your engine builder misses on compression ratio and cam timing and you have to crutch his mistake.

Or, there are times where you need more cam and you can’t tolerate more compression . Then you can get into more initial timing.

IMO if you have to add manifold vacuum to the vacuum advance to make the engine idle you’ve missed somewhere.

Third, look and see if all three of the emulsion holes are drilled out and measure them. Regardless of size (for now) block that middle emulsion hole.

Then lower the idle feed restricters. They stick out like a turd in a punch bowl and they need to go down.

If you search the web for NACA paper number 49 you should download and read it. The stuff in that paper is still correct today and IIRC is nearly or already is 100 years old.

Once you lower the IFR’s you can install T slot restricters.

 

[TT5.9mag]

I can’t see well enough in the pictures but if the T slots are square on both sides secondaries are open too far.

Or there’s an air leak because square T slots isn’t much opening.

Figure that out first.

Second, you will NOT go to hell and burn forever if your T slots aren’t square. I don’t know when it became the do all, be all, end all but it’s not.

Start with them square and tune it from there. If you get them open too far you’ll figure that out.

Second, stop listening to the internet about some spectacularly high initial timing. That’s bullshit.

I forget if you posted your idle vacuum but if you have 20 at a cruise you probably have enough at idle that you don’t need some mega high initial.

You need that when your engine builder misses on compression ratio and cam timing and you have to crutch his mistake.

Or, there are times where you need more cam and you can’t tolerate more compression . Then you can get into more initial timing.

IMO if you have to add manifold vacuum to the vacuum advance to make the engine idle you’ve missed somewhere.

Third, look and see if all three of the emulsion holes are drilled out and measure them. Regardless of size (for now) block that middle emulsion hole.

Then lower the idle feed restricters. They stick out like a turd in a punch bowl and they need to go down.

If you search the web for NACA paper number 49 you should download and read it. The stuff in that paper is still correct today and IIRC is nearly or already is 100 years old.

Once you lower the IFR’s you can install T slot restricters.

Another great post.

 

[TT5.9mag]

The pics are hard to see where the throttle shafts are at. Op, don’t be afraid to take the carb off the engine and get good pics. Lol

 

[TT5.9mag]

I’ve never seen blocks with that emulsion set up.

 

[Hysteric]

Once you lower the IFR’s you can install T slot restricters.

Why bother dicking around with Tslot restrictors when you can just put on a standard holley base plate on and go.

 

[TT5.9mag]

@jmanhoff circled in red is your emulsion stack. Measure those.
Circled in blue is the idle feed restrictor
Circled in green is where the idle feed restriction should be in every carb ever built.

 

[jmanhoff]

I can’t see well enough in the pictures but if the T slots are square on both sides secondaries are open too far.

Or there’s an air leak because square T slots isn’t much opening.

Figure that out first.

Second, you will NOT go to hell and burn forever if your T slots aren’t square. I don’t know when it became the do all, be all, end all but it’s not.

Start with them square and tune it from there. If you get them open too far you’ll figure that out.

Second, stop listening to the internet about some spectacularly high initial timing. That’s bullshit.

I forget if you posted your idle vacuum but if you have 20 at a cruise you probably have enough at idle that you don’t need some mega high initial.

You need that when your engine builder misses on compression ratio and cam timing and you have to crutch his mistake.

Or, there are times where you need more cam and you can’t tolerate more compression . Then you can get into more initial timing.

IMO if you have to add manifold vacuum to the vacuum advance to make the engine idle you’ve missed somewhere.

Third, look and see if all three of the emulsion holes are drilled out and measure them. Regardless of size (for now) block that middle emulsion hole.

Then lower the idle feed restricters. They stick out like a turd in a punch bowl and they need to go down.

If you search the web for NACA paper number 49 you should download and read it. The stuff in that paper is still correct today and IIRC is nearly or already is 100 years old.

Once you lower the IFR’s you can install T slot restricters.

I did lower the timing to 16 degrees, idle went back down a touch to under 900 which is closer to where I would want it. As it sits right now, slow throttle input is super smooth. No bucking, no hesitation, smooth immediate response, but sharp throttle and it cuts. It also looks like I’m not getting a strong squirt from the shooters so maybe it burst the diaphragm? Or would I have basically no squirt at all if that were the case.

In terms of the secondaries, should I close them to the point where it covers their t slot?

I don’t think there’s a vacuum leak because I still have the same amount of vacuum as before and there are no drivability concerns. I’ll have to squirt some brake clean around the carb to see if there is somewhere.

 

[Mattax]

OK. I'll add this because its not going to come up otherwise.
Four corner idle. On this engine, shut them off (turn all the way in) and then just crack 'em.
You can seach four corner idle and poor man's four corner idle for what they do, and you'll understand why I'm saying to basically shut the secondaries to a trickle.

 

[jmanhoff]

@jmanhoff circled in red is your emulsion stack. Measure those.
Circled in blue is the idle feed restrictor
Circled in green is where the idle feed restriction should be in every carb ever built.

View attachment 1716363412

Yeah I saw that on one of the forums posted earlier in this thread. Seems to be a universally disagreed on thing why they were moved to the top lol.

 

[TT5.9mag]

In terms of the secondaries, should I close them to the point where it covers their t slot?

Yes. And turn the needles in for now.

 

[jmanhoff]

OK. I'll add this because its not going to come up otherwise.
Four corner idle. On this engine, shut them off (turn all the way in) and then just crack 'em.
You can seach four corner idle and poor man's four corner idle for what they do, and you'll understand why I'm saying to basically shut the secondaries to a trickle.

Yeah mine are barely open as it sits right now. I’ve read that the brawlers are super sensitive with the 4 corner idle, Holley says to start at a turn and a half out when tuning the idle and if I did that on this carb it would barely run. I start at a half turn out and usually have to go in a quarter turn

 

[jmanhoff]

Yes. And turn the needles in for now.

Okay so closed just until the t slot is covered, then fully close the idle? Or seat then back off a hair

 

[TT5.9mag]

Okay so closed just until the t slot is covered, then fully close the idle? Or seat then back off a hair

Close the secondary butterflies until they are tight in the bores, then barely crack em. Like barely, just so they don’t stick. Then lightly bottom the idle adjustment screws in the secondary block and back them out 1/8 turn. Like @Mattax said. This should be your starting point for a baseline. Tune the primary.

 

[Mattax]

I suppose an 1/8 out fot the secondaries might be OK. Be prepared for the primary mix screws to be a little more shut than typical. I'd prefere a little less on the secondary side since there is so little airflow there, but with high intake vacuum it probably makes no difference.

 

[TT5.9mag]

I said 1/8 just to give a number to it. Rather than say just barely open them.
Also @jmanhoff I had to edit my photo above because I jacked up the first time. It’s correct now.

 

[jmanhoff]

Close the secondary butterflies until they are tight in the bores, then barely crack em. Like barely, just so they don’t stick. Then lightly bottom the idle adjustment screws in the secondary block and back them out 1/8 turn. Like @Mattax said. This should be your starting point for a baseline. Tune the primary.

So I’m basically treating it like a carb that only has primary idle screws in a sense?

 

[TT5.9mag]

So I’m basically treating it like a carb that only has primary idle screws in a sense?

Yes. Your engine has a ton of idle vacuum and as a result will have a very large signal to the carb.