lol I guess I could do that I dont know why that crossed my mind. I just need to buy some more hose. The hose I have hooked up to my current gauge that’s in the truck is larger than the nipple on my “tuning” gauge
Fine Tuning a 360 Magnum with a Brawler "Double Pumper"
- Thread starter jmanhoff
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Alright just went on a drive to work. Engines nice and hot now and the idle (though pig rich still, so not peak vacuum) is 20.5-21”, cruise was hovering around 16-18.
Also go figure, my idle and cruise vacuum seemed stupid high on the other gauge because it’s pegged at 3.5-4” too high. I have it disconnected and swapped it’s place with a different gauge and it’s sitting on my seat reading 4 inches of vacuum not even hooked to anything
Also go figure, my idle and cruise vacuum seemed stupid high on the other gauge because it’s pegged at 3.5-4” too high. I have it disconnected and swapped it’s place with a different gauge and it’s sitting on my seat reading 4 inches of vacuum not even hooked to anything
Get a 10.5 PV in there and if it’s still lean then open the PVCR’s up .010 and test again.
So should I enlarge the TSR first to richen up the transition (if so, how much if I’m already at a rather large .078”) and then also put in a 9.5PV (I know 10.5 was recommended, but a 9.5 I’d imagine will still get me in the ballpark to see if it helps the problem and like I said I have one handy already), and go from there?
I also don’t mean to continue to throw new stuff into the pot but I was also looking at annular boosters, something that came up in some google searches about getting fuel economy down, I currently have straight leg I’m pretty sure, I heard annulars get a stronger signal sooner meaning I can really lean out the idle/transition and still have a good transfer over to the mains without having a lean stumble, but I also heard if you do run annulars, you need to tweak everything because it changes a lot.
I also don’t mean to continue to throw new stuff into the pot but I was also looking at annular boosters, something that came up in some google searches about getting fuel economy down, I currently have straight leg I’m pretty sure, I heard annulars get a stronger signal sooner meaning I can really lean out the idle/transition and still have a good transfer over to the mains without having a lean stumble, but I also heard if you do run annulars, you need to tweak everything because it changes a lot.
Do the PV first. It may not need MORE fuel, it may need the fuel EARLIER.
If you are going to use annular booster, call Mark Whitener and buy his.
Lightning Racing Carbs.
To that end, you will need to change your tune up by a long ways. You can’t or at least you shouldn’t just press them in and send it.
Not all boosters are the same. The size, shape an the number and size of the holes all affect the characteristics of the booster and how it affects the fuel curve and carb tuning.
I’ve never used those but I’ve read other people who have used them and I’ve never read about an issue with them.
I say give them a shot. Just know you will need to make some changes in your carb tune. And depending on how they affect airflow and how much more pressure drop across the booster you get you can end up with some wild or at least some unorthodox tuning in the carb.
So if you need far less emulsion and a really small MAB don’t get married to orthodox bleed numbers. And you’ll most likely end up using much smaller jets than would seem reasonable.
So it’s a lot of back and forth stuff? I’ve heard the annulars are better for daily/low end fueling and suffer in the top end, which doesn’t really matter to me.
I’m just hoping I can run a really lean transition and still keep it safe once I crack open the throttle, that’s my goal. This truck with this cam barely does anything to stay moving down the highway, so I can really get some good mpg if I can run it lean
You do NOT have to sacrifice top end power for driveability. Nor should you.
That was what I was saying above. I have 850 CFM carbs out there with the booster I use that run on primary jets between 66 and 69, PVCR’s in the mid to high 60’s (and thats a touch far but I err on the side of caution there) T slot restricters no bigger than .070 and secondary jets in the high 70’s.
That absolutely drives some guys wild because rather than giving the engine what it wants, they tune to what is considered “orthodox” jetting for any given Venturi and throttle blade size.
They think that if your jetting doesn’t fall into what has been used for decades without regard to booster design then they go off the cliff and run them fat and they didn’t fix anything.
I promise you that you’ll end up with a main air bleed no bigger than .028 and if the booster works very well you may go as small as .024.
The smaller the main air bleed, the later the booster starts so you are leaner at low throttle opening.
And at WOT that small air bleed doesn’t bleed off as much signal so the fuel curve goes pig rich up there. That’s where the much smaller main jet comes in.
All the emulsion bleeds and air bleeds and booster design all affect each other. The trick is figuring out how the trim the fuel curve when it goes fat or lean.
PRH
Well-Known Member
The easy button for trying out some annular boosters…….without it messing up your current configuration:
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TT5.9mag
Two atmospheres are better than one
I’ll just say this, you can make awesome fuel mileage with any kind of booster when you have the kind of signal you’re going to have with a 208@050 cam on 360 inches. I vote leave the booster alone for now, tune what you have. Get the ignition system dialed in tits (which is where a LOT of the fuel economy will come from) and then change the booster if you desire to.
TT5.9mag
Two atmospheres are better than one
We need a “love” button. The “like” button doesn’t do this comment justice.
okay everything seems to be clicking now. That was my main selling point with the annulars was I could run leaner jets because of the way they get their signal, and I could tweak WOT with the PVCR. Right now I have 28 MABs and the current wot is pretty rich so I would think I would go with smaller jets regardless of what booster I use. I also like the idea of staying on the slightly richer side, because being too rich at big load doesn’t break things like lean does.
Even though I have a cheap Chinese HEI clone, it seems pretty strong ignition wise. I have 20 degrees initial (I haven’t really messed with the timing since putting the new cam in, but I don’t get any pinging at all), and I have ported vacuum. I want to get an adjustable can so I can tweak when the vacuum comes in, and I also need to start messing with the mechanical curve. From what I’ve read it’s basically give it as much advance as you can when cruising but balance it out with the mechanical advance so it doesn’t ping anywhere in the rpm curve.
Even though I have a cheap Chinese HEI clone, it seems pretty strong ignition wise. I have 20 degrees initial (I haven’t really messed with the timing since putting the new cam in, but I don’t get any pinging at all), and I have ported vacuum. I want to get an adjustable can so I can tweak when the vacuum comes in, and I also need to start messing with the mechanical curve. From what I’ve read it’s basically give it as much advance as you can when cruising but balance it out with the mechanical advance so it doesn’t ping anywhere in the rpm curve.
As TT5.9 says you have so much vacuum you’ll have no issue with signal.
You should be able to make what you have get fuel mileage that will make a Honda blush.
You just have to keep tuning on it.
That said, if you do change boosters you have to remember one other thing I always forget to mention.
If your manifold has heat under it and you increase booster signal and atomization you can end up with too much vapor in the runners and cylinder. That displaces air and drops your VE and power.
You can over atomize the fuel and drop power. If your manifold has aren’t concerned about power then thats not an issue.
It’s an RPM air gap if that helps anything. I’m prioritizing torque over horsepower, it’s a truck not a hot rod of course lol. I like learning about how all this stuff works too, experimenting is fun. It’s funny how before I thought carbs were more simple than EFI, but boy was I wrong.
When I did this test on the dyno the main circuit started at the same rpm no matter what size bleed I put in it. I even took the bleed clear out and it didn't change when the booster started flowing. It was an easy test to do. Try it sometime on your dyno and report back the results. My test may have been a fluke
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As others have said this sounds like the power valve is not kicking in soon enough. If this is your main concern try a bigger number powervalve and see if that changes for the better and go from there. Also I might have missed the reason, but why are you running your idle mixture rich?
TT5.9mag
Two atmospheres are better than one
Seems like you have as much ignition timing tuning to do as you’ve had carb tuning.
Very much so, I’ve been on the fence for awhile about messing with the HEI clone or just buying an actual MSD box or all in one and balancing the time is hard too because the truck is currently my only vehicle.
TT5.9mag
Two atmospheres are better than one
If you’re driving it, you need to get the timing sorted out. Timing can break stuff. Get the total advance set to 34 degrees and disconnect the vacuum advance for now. It’ll be safe there.
Is it pinging or hesitating or surging when running on transition with the idle mixture set properly?
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