Newbomb Turk
Well-Known Member
Yes. It’s so far you can take almost all the fuel from the idle circuit to make it idle.
So either it’s just that fat or the throttle is open far enough that you’re getting fuel from the T slots or both.
Fine Tuning a 360 Magnum with a Brawler "Double Pumper"
- Thread starter jmanhoff
- Start date
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Yes. It’s so far you can take almost all the fuel from the idle circuit to make it idle.
So either it’s just that fat or the throttle is open far enough that you’re getting fuel from the T slots or both.
I think even with the t slot completely covered I can still turn the screws almost all the way in and it runs lol. One and a half turns out it barely runs
Newbomb Turk
Well-Known Member
If I'm trying to determine how far off I am I'll throw a HUGE idle air bleed in it and see what happens. Like .088 or something like that.
If the screws come out to where they should be then I know it's THAT fat and I go back in and drop the idle feed restriction down and put the correct size idle air bleed in it and then tune some more.
That makes sense, I’m probably just going to put in a .028 IFR anyway just because I feel like it’s more likely the IFR would be larger than stamped not smaller than stamped, feel like that wouldn’t make any sense lol.
TT5.9mag
Two atmospheres are better than one
There’s really no need to buy a pv block off for initial tuning of the main, the best way to tune the main jets is just to steady cruise and keep peeling jet out of it until it surges on cruise then add one or two sizes back and be done. You don’t load the engine hard enough to get in to PV when trying to set the main jet.
Newbomb Turk
Well-Known Member
This is true. You really need a vacuum gauge in the car with you so you can watch vacuum too while your doing this.
So once I get to this point, should I go down in jets until it won't CRUISE without surging or until it won't load up without surging? Or am I going down until it surges, up two, then looking at what vacuum reading it surges while loading and then getting a PV for that reading?
TT5.9mag
Two atmospheres are better than one
Once you get it to surge cruising, go up a jet size or two, and leave it there. You then tune wot fuel with the power valve channel restrictors. You set the TIME when you want the PV to come in with the number on the PV. Your combo with so much vacuum will probably want a 10.5 PV or so.
Okay that clicked. I may try a 65 jet because it surged EVER so slightly on 64s, granted that was also with the carb backward so it could’ve just been starving for fuel
TT5.9mag
Two atmospheres are better than one
That’s what the surging is, the engine starving for fuel. Won’t matter if the carb is backwards or not as long as it was sealed up. Once it surges that’s as lean (cruise) as the engine will tolerate, and usually that’s around 15.5:1 AFR. I try to get mild stuff to cruise in the 14.8-15.0 range. So one or two jet sizes. And that will get you some fuel mileage, if you use ported vacuum advance it will get even better.
Yeah ive been sticking to ported, keeps my idle significantly lower lol. Doing dominos my mpg has been about 8.5-9 which is what I would expect as I’m in a college town so I’m constantly stopping and doing a lot of idling. I’m sure once I get the idle and t slot restrictors and bleeds figured out that will go up, I don’t think I’m really getting into the main jets at least for longer than a couple of seconds because I keep the rpm’s low.
Cruising down the highway though I’m sure if I can tune the main bleed and emulsion right and drop down the main jet even slightly I can get better mpg. The best I got on the setup as it stands right now was 16mpg which is almost what the v6 got, so I’m sure there’s some more I can milk out. Maybe once I get the carb tuned I can play with timing/plug gap. I have the stock .035 gap right now which is what the older trucks wanted, newer did .040 but I’ve read .045 is doable with HEI which I have.
TT5.9mag
Two atmospheres are better than one
You can run the gap up to .050 but it won’t make much difference. Mileage will come from cruise timing. Once you get the carb sorted out we’ll guide you through pulling in 45-50 degrees of timing at cruise and the fuel mileage will come.
Sounds like a plan, I still don’t really understand how those vacuum canisters work lol. I currently have one on that I think is for a small block Chevy, granted it is Chevy style HEI, but it’s not the original canister that came with the distributor. I somehow blew the original out, no idea how, so I have no idea what the timing curve for it looks lol.
TT5.9mag
Two atmospheres are better than one
They’re just a diaphragm inside a can. When vacuum is applied to one side it creates movement. There is an arm attached to the non vacuum side and that arm pulls on the reluctor plate inside the distributor, advancing the timing. Very very simple and effective device.
Isn’t there some like Allen key adjustment inside of the vacuum port that you can adjust when the advance comes in or something
Newbomb Turk
Well-Known Member
If it’s a Chrysler distributor and it has a hex on the vacuum can it’s adjustable.
Most of the Mallory distributors I have and have done had adjustable vacuum cans.
I’m pretty sure @Mattax has posted some templates for working out your timing curve in the car. It can be done and really should be done.
I can say it’s way way easier and 10 times faster if you have a distributor test bench.
It’s even easier if you have it on a dyno and you have a distributor test bench right there.
FWIW I’ll most likely be the only guy running tunnel ram and vacuum advance on my engine. I’m pretty sure I can make it work.
I gotta do some research to see if there’s even a dyno shop around me. I would love to get this thing on the dyno to see what it makes
TT5.9mag
Two atmospheres are better than one
Yea the Allen adjustment will add or subtract preload on the spring in the diaphragm and change when the advance starts to come in. Kinda like a power valve.
Yeah that’s the thing I gotta learn to understand lol. Oh well, we’ll build that bridge when we get there. I need to map my timing curve out first too obviously.
So while I have the carb off when I change the IFRs and stuff, I wanted to take a peak at the accelerator pump circuit. Not tuning wise, just trying to figure out the squirt issue.
Even though I swapped diaphragms I still have a weak shot until about halfway into the primaries, at that point it’s strong. Clogged passages?
I know there’s a check valve so should I get some carb cleaner with the red straw and spray it though the bowl side of the passage then pull the nozzle off, clean that, and spray from the top?
Even though I swapped diaphragms I still have a weak shot until about halfway into the primaries, at that point it’s strong. Clogged passages?
I know there’s a check valve so should I get some carb cleaner with the red straw and spray it though the bowl side of the passage then pull the nozzle off, clean that, and spray from the top?
TT5.9mag
Two atmospheres are better than one
The timing and duration of the pump shot is all in the adjustment of the arm and the shape of the cam. What pump shot cam is on it? Color? Make sure the nozzles in the shooter are clear and open
It’s currently the white one? I dont know I’m colorblind so it could be pink. Stock cam with 3 holes.
I know the cam dictates basically everything but when I articulate the throttle linkage I can see the linkage move the arm. If I slowly move it I have barely any pump shot until halfway, quickly moving it it is there, just weak
Newbomb Turk
Well-Known Member
If it has 3 holes it’s the pink cam.
I pretty much use the blue cam on everything anymore.
But you have to bend the pump arm where it rides on the cam so it lays flat on the cam like it should.
Yeah I’ll be buying the cam kit next, just want to get everything sorted out bleed and restrictor wise first.
Just trying to figure out why it’s not spraying, hopefully it’s just some build up or something
If you install the pink cam upside down, it will act very much like the blue cam. You may have to bend the pump arm. I have done this several times and it has worked well. I can't remember which hole to use when you flip it upside down, but remember it was pretty obvious. I know you said you don't like reading, but here is a thread that explains it.
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