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

-
Newbomb Turk said:
OUTSTANDING!!!! I love progress. Keep chipping away at it and you’ll have EFI drivability and carbureted horsepower.
Click to expand...
Have a lot of very random things to deal with, I do plan to get a different style cable which will probably help.

I replaced my voltage regulator and now my voltage isn’t going crazy and it’s lower on the gauge (granted it’s a mopar so how trustable that is, meh), but my fuel pressure went down to about 5psi which I think I remember someone saying is better for street holleys, I just need to adjust the bowls again.
 
So after my shift, really the only takeaway I have other than the power and responsiveness I finally have out of this carb is it seems like if I barely have my foot on the throttle it falls on its face, but I’m not entirely sure if it’s the carbs fault or if the amount I’m pressing down the throttle is just letting the slack out of the cable and I’m really at idle and it’s stumbling because I’m letting out the clutch without giving any throttle.

Do you guys usually have slack in your cables or do you leave it nice and tight?
 
jmanhoff said:
So after my shift, really the only takeaway I have other than the power and responsiveness I finally have out of this carb is it seems like if I barely have my foot on the throttle it falls on its face, but I’m not entirely sure if it’s the carbs fault or if the amount I’m pressing down the throttle is just letting the slack out of the cable and I’m really at idle and it’s stumbling because I’m letting out the clutch without giving any throttle.

Do you guys usually have slack in your cables or do you leave it nice and tight?
Click to expand...


Engines move around. Quite a bit. So there needs to be SOME slack in the cable or you take the chance of the engine moving and opening the throttle.

I take my finger and push on the cable between the carb and the cable mount. If moves an 1/8 of an inch I send it.

If you have solid engine mounts you can run it a skosh tighter than that but you still need some slack.
 
Newbomb Turk said:
Engines move around. Quite a bit. So there needs to be SOME slack in the cable or you take the chance of the engine moving and opening the throttle.

I take my finger and push on the cable between the carb and the cable mount. If moves an 1/8 of an inch I send it.

If you have solid engine mounts you can run it a skosh tighter than that but you still need some slack.
Click to expand...

Makes sense. I have rubber mounts still I think I would lose my mind with solid mounts in this truck lol. The cable has quite a bit of slack in it, but not a lot of that makes sense. I can take a video if I need to.

I feel like a slightly tighter cable will also let the throttle snap fully shut because the spring has more leverage on the cable
 
I usually set the curb idle where I want it with the cable disconnected, then make sure the cable has enough slack to “fall together” if that makes any sense. Should be tight but not taught. Minimal slack.
 
TT5.9mag said:
I usually set the curb idle where I want it with the cable disconnected, then make sure the cable has enough slack to “fall together” if that makes any sense. Should be tight but not taught. Minimal slack.
Click to expand...

I think the big issue is the bracket that I have now, technically it’s for something like a Sniper but it still works pretty much the same as a carb throttle cable bracket. I did notice that the bracket that holds the tension for the cable is ever so slightly offset from the throttle lever so it’s possible that the cable is sticking because it’s sawing into the plastic for the tensioner and its binding.

I have a new cable with like a through bolt style tensioner instead of the plastic clip as well as an actual carb throttle bracket to order once spring break is over.
 
Try a little stiffer throttle return spring. Keep working on it your getting there. P. S. my 770 VC Brawler already had everything drill and threaded. The one you have must be much older. The only thing I had to fix was the IFR, of course because these manufacturers just insist on the upper position.
 
Carnut68 said:
Try a little stiffer throttle return spring. Keep working on it your getting there. P. S. my 770 VC Brawler already had everything drill and threaded. The one you have must be much older. The only thing I had to fix was the IFR, of course because these manufacturers just insist on the upper position.
Click to expand...

I’m not sure if it’s the return spring but I have tried the dual spring setup, with the two that go inside of each other and the pedal gets so stiff that I basically have to stand on the pedal to get it to move.

I’m currently using one of the dual springs, being the larger one that goes over the skinny one if that makes sense.
 
Couple more questions:

In terms of tuning the t-slot restrictor size/IAB, should I just continue to drive around and check the plugs and log what the plugs look like as well as what the truck feels like driving?

Also, with the choke, I heard that a lot of the "newer" engines that are higher compression than the motors say from the 70s and 80s don't need a choke because they're so "efficient" to begin with, being higher compression. I also know, especially in the case of a modern engine, that the electric choke is way too slow to open. In my case, even with the choke set to open sooner, I think its 3 ticks to the right from the center mark, it seems like it is way too much. 50 degrees outside today, and when I started it cold it starts right up and then it starts to sort of stumble, and if I do literally anything to put a load on the engine (like turning to pull out of a parking spot) it will die, but it doesn't seem like its a lean stumble die, it kind of sputters to death. If I wait awhile and start to drive slowly through the parking lot it sounds like its misfiring and has a very sooty exhaust cloud for a minute then clears up.

Should I just invest in a manual choke so I can have it closed to start and then immediately open it? I know this engine likes the high idle when cold as I'm sure most do, but it seems like the choke is causing more issues. Is the Magnum considered a "high compression" motor when it comes to carbureted applications? I know that its about 9:1 but that's not high in modern standards.
 
Sounds like you need to get in to how to adjust a choke properly. Which includes the air flap adjustment and the high idle adjustment. The black sootyness is overly rich (which is the purpose of a choke) but you need to make sure it turns off at the correct time, and that’s when some heat builds in the intake sufficient enough that the fuel no longer puddles. I hate chokes, no carburetor I have has a choke left on it. But I live in California and have never needed one. With regards to modern stuff, all factory calibrations have “choke like” settings in warm up tables that do exactly the same thing as a choke. It’s not because of efficiency or compression or anything else except modern efi.
 
While you are tuning the circuits of the carb, I would wire the choke wide open, disconnect any wiring and eliminate it completely. Use your right foot to warm the engine up before driving. After your tune is squared away you can add the choke back in.
 
TT5.9mag said:
While you are tuning the circuits of the carb, I would wire the choke wide open, disconnect any wiring and eliminate it completely. Use your right foot to warm the engine up before driving. After your tune is squared away you can add the choke back in.
Click to expand...

Seems like something I should’ve done I think it was mentioned before lol. I know the basic function of the choke but I didn’t know that fuel would pool in a cold intake so that’s new to me. I know this engine will run with the choke open when it’s cold as when it’s stumbling on a cold start I can open the flap and the idle smooths right out even after only running for 20 seconds or so.
 
After awhile of driving it on the current setup, it seems much better. My MPG is slowly creeping higher than it was before (especially since I've stopped romping on it at every red light), still need to play with the mixture and maybe restrictors as when I set the idle to highest vacuum then richen slightly (like 1/8 of a turn) it still smells really rich, even with the cats. The weather has been extremely inconsistent recently, it was 70 yesterday and today its snowing, so I've been leaving it as it is. I'm going to Florida for spring break and I won't be back until next Thursday the 14th so I won't be able to do any monkeying until then. Hopefully the weather stabilizes enough where I can actually tune in a more controlled environment lol.
 
Alright, back from break and back to work and back with potentially stupid questions.

After driving around for awhile, I’m still having a dieseling issue, and if I close the idle screw more the vacuum drops quite a bit and the idle screws need to be almost completely in for it to be happy. Is there a spot the screws are “supposed” to be in relation to your IFR and IAB sizes?

When I close the idle screw a bit to get the dieseling to stop it seems like there’s a slight dead spot on slight throttle coming out from a stop, almost like it’s not getting enough fuel it seems like (engine sounds like it cuts), but the idle smells pig rich.

I want to pull a couple plugs to show pictures, but was curious, what should I do driving wise prior to pulling them? Or does it not really matter

To avoid any scrolling:
IFR: .028
IAB: .070
TSR: .070
Idle mixture: 3/4 turn out

MAB: .028
Timing: 13° @ 750rpm
PMJ: #66

Middle emulsion ports blocked, top and bottom not touched
 
jmanhoff said:
I want to pull a couple plugs to show pictures, but was curious, what should I do driving wise prior to pulling them? Or does it not really matter
Click to expand...
Avoid prolonged periods of idling.
 
Hysteric said:
Avoid prolonged periods of idling.
Click to expand...
So, as I’m currently tuning the idle and transfer circuit, should I drive around normally, not romping on it, more cruising around for a couple of minutes then park, immediately shut it off, then check the plugs?
 
jmanhoff said:
So, as I’m currently tuning the idle and transfer circuit, should I drive around normally, not romping on it, more cruising around for a couple of minutes then park, immediately shut it off, then check the plugs?
Click to expand...
Yes. Take it out for a drive and when you get back don't let it sit idling.
 
jmanhoff said:
Alright, back from break and back to work and back with potentially stupid questions.

After driving around for awhile, I’m still having a dieseling issue, and if I close the idle screw more the vacuum drops quite a bit and the idle screws need to be almost completely in for it to be happy. Is there a spot the screws are “supposed” to be in relation to your IFR and IAB sizes?

When I close the idle screw a bit to get the dieseling to stop it seems like there’s a slight dead spot on slight throttle coming out from a stop, almost like it’s not getting enough fuel it seems like (engine sounds like it cuts), but the idle smells pig rich.

I want to pull a couple plugs to show pictures, but was curious, what should I do driving wise prior to pulling them? Or does it not really matter

To avoid any scrolling:
IFR: .028
IAB: .070
TSR: .070
Idle mixture: 3/4 turn out

MAB: .028
Timing: 13° @ 750rpm
PMJ: #66

Middle emulsion ports blocked, top and bottom not touched
Click to expand...

Don’t touch the carb. Take it off (yes you can touch it while taking it off…I should have said that first and typed less) flip it over and look at how much T slot exposure you have.

If over 50% of the slot is open, you need to drill some SMALL holes in each butterfly.

This takes time and patience because you need to sneak up on it. If you make them too big the engine will idle high with the butterflies shut.

Drill the holes in line with the curb idle discharge port. Stay about 3/16 away from the edge of the butterfly so you can start small and sneak up on it. If you start out too close to the edge and you need to go bigger on the hole you can’t because you’ll blow through the edge of the butterfly.

SNEAK UP ON IT.

If the butterflies are showing less than 50% of the T slot you have too hot of a plug, engine coolant too hot, not enough octane for the fuel you are using or some or all of them.

I forget if you know the compression ratio or not.
 
Alright I’ll check the t slot tomorrow, hopefully going to get in my new throttle cable and bracket before I leave for work.

The compression ratio shouldn’t be notably higher than stock, stock replacement heads, stock replacement pistons but .020 over. The block was decked, potentially the amount is on the receipt somewhere. I think the magnums float around 9:1?

I don’t believe this engine is a hot runner, I’ve lasered the tanks on the rad and it read about 160 so probably 180 inside, the dummy gauge doesn’t even go to half on the dash, it sits around a quarter.

I’m currently running autolite plugs, not entirely sure what they are I bought them at advance auto, they are supposedly a direct replacement to RC12YC? Whatever the champion stock plugs were.

I’m running 87 octane currently.
 
Another interesting thing that just came up, I’m going to check my fuel bowl level again but when idling for a couple of minutes (delivering pizza leaving the engine running) it starts to idle lower and lower. I left the truck with it idling at 700, now it’s idling down to 400 and vacuum dropped from 20 to 15, but if I give it gas everything is back to normal.

I am also getting slight bucking when around 1500rpm and barely on the throttle (cruising), it’s not horrible but it’s enough to move me back and forth in the seat.
 
jmanhoff said:
Alright I’ll check the t slot tomorrow, hopefully going to get in my new throttle cable and bracket before I leave for work.

The compression ratio shouldn’t be notably higher than stock, stock replacement heads, stock replacement pistons but .020 over. The block was decked, potentially the amount is on the receipt somewhere. I think the magnums float around 9:1?

I don’t believe this engine is a hot runner, I’ve lasered the tanks on the rad and it read about 160 so probably 180 inside, the dummy gauge doesn’t even go to half on the dash, it sits around a quarter.

I’m currently running autolite plugs, not entirely sure what they are I bought them at advance auto, they are supposedly a direct replacement to RC12YC? Whatever the champion stock plugs were.

I’m running 87 octane currently.
Click to expand...


You need to NOT use 87 ever in a car like yours.

87 octane is mostly fillers and junk. The Regulations regarding what can and can’t used in it.

Premium pump fuel has way tighter control over its formulation. It has far less fillers and whatever other junk they use on 87 octane fuel.
 
To follow up on the lowering idle, the secondary float got gummed up and stuck open, flooding the secondary throat. I’m not sure why this would happen twice within a short period of time unless my filter isn’t doing anything, but I do have technically 3 filters on this truck.
 
Newbomb Turk said:
You need to NOT use 87 ever in a car like yours.

87 octane is mostly fillers and junk. The Regulations regarding what can and can’t used in it.

Premium pump fuel has way tighter control over its formulation. It has far less fillers and whatever other junk they use on 87 octane fuel.
Click to expand...
How do you feel about 89 or 91? Those are more readily available than 93 around me.
 
Newbomb Turk said:
91. Always use the highest grade they have.

Regardless of the octane rating the highest grade is the most regulated.
Click to expand...

I’m currently at Walmart where they have 93 for $2.99 a gallon, how they get it that low is beyond me. Probably will start coming here from now on to full this thing up. The gas station I go to that has cheap 87 has 3.69/gal 93
 
You must log in or register to reply here.
-

Back
Top