IRISH RT
Well-Known Member
Anyone ever done this with an Edelbrock and got good results ?????
Reverse Jetting
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OldmanRick
Well-Known Member
I suppose you're talking about leaning one out? I've done it a few times with Holley's, but in general, anything more then a "step" leaned them too far. If we're on the same page, we are talking about the primary side here? The factory setup on most street carbs is about as lean as they like to run, from what I've seen.
If you're trying to lean a "big" carb to run on a mild combo, while worthy of trying, I'd look to step down to a smaller unit at some point.
If you're trying to lean a "big" carb to run on a mild combo, while worthy of trying, I'd look to step down to a smaller unit at some point.
IRISH RT
Well-Known Member
Exactly Eddy carbs work sort of oposite to holley Jet wise I know there are also power valve and needle differences,
Took My Street strip trip on a Long trip last decided to get it lean as possible for some economy So had 107 in the primaries and 104 in the secondaries and 65 /37 needles i went real well a tad to lean But strong Screamed when pushed now first drag meeting of the season here for me new combo 360 ,727 3500 stall 3.9 rear
So I need to fatten it up so I went 110 Primary and 107 Secondaries
, And It has not the Same Crisp Response , Yes Reverse To Standard Eddy Jetting , Back to front some would say
IRISH RT
Well-Known Member
Yes But On The Street You Not out of the Primaries Very Often unless your over half throttle or WOT, So Why do the Primaries Have To be Rich , Its The Secondaries that Matter At Full Noise ,
hotstuff1
Well-Known Member
I have had better luck tuning , by changing the step-up springs . If that fails , I change the jets and metering rods
bobtile
Well-Known Member
The smaller Eddy carbs are the opposite. Up to 600 cfm I believe the primaries are smaller than the secondaries.
TrailBeast
AKA Mopars4us on Youtube
They are physically the same size (will interchange) on my 600, but smaller ID by a few steps in the secondaries out of the box .
360duster
Well-Known Member
tony was talking about the jets. And he´s right ;-))
bobtile
Well-Known Member
I was talking about jetting, not physical size. Sorry for not wording that correctly.
TrailBeast
AKA Mopars4us on Youtube
TrailBeast
AKA Mopars4us on Youtube
That's what I meant also.
The primary jets were smaller than the secondaries.
I just mentioned physical size as a side note.
How the heck did I double post.
The jet/orfice size should be for the correct A/F ranges throughout the RPM band. If that means it's done while upside down in a trash can to get right, so be it.
At full thottle, provided same size throttle bores, you would like as close to a 50/50 distribution from primary and secondary bores. Putting smaller jets up front with a rod stuck in it may cause distribution to become unbalanced. Having the front feed 40% or less and the rear 60% or more will not be a good set up and cause rich back cylinders, lean front, even though it all drop into the same mixing hole and be a 100% number.
As Tony stated:
The metering rod is the reason the primary jet is larger. If someone told you that was wrong, you need to do some math to calculate surface area of the opening. The amount/area a rod takes away from the opening is a big factor in why you usually have a larger jet up front. The rod is down in the jet all the time, even at WOT. That's how it meters for LESS fuel when you aren't on it.
Grab a book on how carter or AVS style carbs work, it will help explain the design/methodology.
At full thottle, provided same size throttle bores, you would like as close to a 50/50 distribution from primary and secondary bores. Putting smaller jets up front with a rod stuck in it may cause distribution to become unbalanced. Having the front feed 40% or less and the rear 60% or more will not be a good set up and cause rich back cylinders, lean front, even though it all drop into the same mixing hole and be a 100% number.
As Tony stated:
The metering rod is the reason the primary jet is larger. If someone told you that was wrong, you need to do some math to calculate surface area of the opening. The amount/area a rod takes away from the opening is a big factor in why you usually have a larger jet up front. The rod is down in the jet all the time, even at WOT. That's how it meters for LESS fuel when you aren't on it.
Grab a book on how carter or AVS style carbs work, it will help explain the design/methodology.
TrailBeast
AKA Mopars4us on Youtube
The jet/orfice size should be for the correct A/F ranges throughout the RPM band. If that means it's done while upside down in a trash can to get right, so be it.
At full thottle, provided same size throttle bores, you would like as close to a 50/50 distribution from primary and secondary bores. Putting smaller jets up front with a rod stuck in it may cause distribution to become unbalanced. Having the front feed 40% or less and the rear 60% or more will not be a good set up and cause rich back cylinders, lean front, even though it all drop into the same mixing hole and be a 100% number.
As Tony stated:
The metering rod is the reason the primary jet is larger. If someone told you that was wrong, you need to do some math to calculate surface area of the opening. The amount/area a rod takes away from the opening is a big factor in why you usually have a larger jet up front. The rod is down in the jet all the time, even at WOT. That's how it meters for LESS fuel when you aren't on it.
Grab a book on how carter or AVS style carbs work, it will help explain the design/methodology.
And that is why I run .098 all around but plan to drop the secondaries down a size or two. (the needles in the primaries)
I run about 14 to 1 or so in all ranges exept my WOT is a bit fat, so .094 in the secondaries should get it pretty close to good A/F ratio as well as a decent balance. (square bore carb)
IRISH RT
Well-Known Member
So what engine are you running 98s on , I need a mininium of 104 on a worked 360, its so hard to read plugs these days with all the additives in current fuels, so trying to tune by the seat of my pants my first jet combo yielded more more power through the range ,have done a couple of thousand miles on the street with my first combo , just dont know if its a little lean for the 1/4,
Can you use a carter strip kit on edelbrock carbs???
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Yes. If you can find an original Carter AFB tuning kit grab it as it has a few things extra the edelbrock kit doesnt.
I dont understand it when people say that new fuels dont colour plugs. Carbon is the by product of combustion that colours the plug. IF your plugs are white its lean so add jet till you get some colour and go from there.
Hysteric
TrailBeast
AKA Mopars4us on Youtube
My car is a daily driver so that would make a difference because I tune for fuel economy.
I have a stock block 318 with 1 5/8 tubes, 3" collectors and 2.5 pipe through flowmasters.
I do know the car feels a little stronger if it's a hair richer. 13-13.5 or so.
The thing I don't like about plug color tuning is that you pretty much have to have a wide open area of road to do do it right, because it throws your readings off if you run the engine in any range other than the range you are testing for.
Since I have an A/F guage I use that for getting it dialed in and then use seat of the pants and plugs to get it where I want it.
For example, if I try to run 14 to 1 or higher on the idle it gets kind of squeemish feeling and misses a little (until it is FULLY warmed up)
At about 12.5 or 13 it idles nice and smooth as soon as the choke releases all the way.
I personally don't know about the Carter kit.
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