Ok, so in a previous post I asked some questions regarding my carb which came off some unknown Ford product. It has reverse idle screws, and I just wasn't getting it dialed in like I wanted.

Someone on the board (DI?) suggested I swap out the metering plate w/ a stock one, and it might get me what I wanted. Well, after piddling with it this weekend, here's what I found.

The OEM metering plate looks like this:

Note the circled area.

The aftermarket plate looks like this:

Again, note the circled area.

Now, at first, I had hoped I would just be able to swap on the new plate and I would be in business. But then I looked on the carb to see the corresponding mating surface and saw this:



I didn't have a spare gasket, so I didn't pull the old one off and investigate underneath, but I'm willing to bet there's no holes to mate up with it on the carb body. I'll dig deeper into it this week. (I had to count on it to get me back to school today, so I didn't wanna tear too far into it this weekend.)

I figured I didn't have anything to lose if I swapped metering plates anyway, so I went ahead and tried it. It didn't change the behavior of the idle adjustment screws much (although now it likes about 1 full turn out from the seat as opposed to being tight against it), but it no longer "smells" lean. I didn't pull the plugs to check what they looked like, but I'm not sure that's an accurate method when checking idle anyway.

At this point, I guess the question is, what function are these missing holes supposed to accomplish? Argentina, you seem to know these carbs inside and out, so maybe you can shed some light on this.

Finally, in the previous post, I know someone (Joshie?) referred to it as an "Economaster" carb. From what I understand, the Economaster variants usually had better fuel distribution. Here's a shot down the throttle bores (poor photoshop work to remove the shadow is mine; I was in a hurry):




Are these odd venturis an asset or a liability in terms of performance?

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Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

Argentina's the guy to comment on the metering block differences. Those star-booster venturis flow less air than standard ones, but do a better job of atomising the fuel and pick up a stronger vacuum signal. So, maximum flow is less, but unless you're running at or near full throttle all the time, the star-booster setup is good for street driveability and MPGs.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

1st sorry about the first grader kinda drawings.

here we go:



here we have side by side your 2 snaps oriented as the surfaces mates.

that area you've circled there is the air emulsion stages part. Your OEM plate has only 1 air emulsion stages. My custom metering plates have as much as 5 holes lined up in the metering plate. The more air bleeds you have there, the more stable that the mixture gets, so you'll have better atomization, better mixture and less tendency to get rich on one side right on the other (that's a great holley 2300 tendency when those carbs are used on small CI engines such as the slant...) That mates with the yellow circle on the carb body side. That passage leads to the smaller air bleed hole (the ones that are near the accel pump nozzle) The economaster you have there produces better signal (hence more fuel is drawn at the same vac readings compared to a regular 2300 venturi) so the high speed air bleed is larger (to compensate by adding more air)

The red passages are the idle passages, the transfer slot sees the fuel from the main circuit minus the restriction in the idle feed channel but plus the air from the "large" (aka idle air bleed) air bleed and the idle adjusted by the screw circuit sees the main circuit minus the idle feed chanel restriction minus the amount of fuel plus the air from the idle air bleed (mixture)

when your car's at idle, engine is fed by the idle discharge hole below throttle plates plus the amount of fuel that exposition of transfer slots might give if there's any. At idle, your mixture is controlled by the idle adjust screw. Air is controlled by the actuating air bleed (idle) and the amount of air that htrottle plates might let go into the engine (again, if there's any)

As you slowsly accelerate, the transfer slot adds more fuel to "fill in" untill the airflow is enough to be metered by the main circuit. Accel pump also "fills in" till transfer slot kicks in. Since a carb meters the fuel by pressure differentials, the transitional flow from one channel to another isn't always instantly swapped so there's intermediate devices such as accel pumps and transfer slots...

when you accelerate, the fuel bowl changes its level, if you accelerate hard or near wot all the time, the fuel will lower enough to expose those emulsion stage holes, adding more "correction" to the mixture (more air). The higher those holes are, the sooner they start to introduce air into the mixture (so, they lean out the mixture)

Given your configuration, I'd do this:

A) restriction in flow: those 2300 are plenty for a slant. The economaster venturis would give you great power and crisper throttle response compromise. That is to say you'd be better than with a BBD (I hate BBD's, I know 90% of slanters up there love them but I hate them) yet better than with a regular 2300 in terms of throttle response.

B) metering plate: I's use any aftermarket plate with more than 2 emulsion stages and regular idle screw (not reversed) if there's a chance I'd use any metering plate from any mopar application. More than 2 emulsion stages and you might want to go to larger jets to compensate for the extra correction.

C)accel pump nozzle (if you were fine before I wouldn't touch that untill I fine tuned all the metering plate chnge part)


Remember that you should be able to kill the engine if you close only one idle screw, if that doesn't happen you're way too rich at idle, you might want to use smaller jets or if you're happy with the compromise between fuel economy and power, you want to drill small holes on the throttle blades on the opposite side of the transfer slot. Holley says that the hole should be drilled on the same side, I drill them on the other side because that has yielded better results in my experience...

any other thing that I'm not being clear about (it's 1 am down here) I'm sure that DI can chime in and correct me if I'm wrong or lighten my explanation even more. Anyway Ill be checking this topic tomorrow.

BTW I found an OLD reply to your clarinet e-mail stuked in my unsent drafts folder... I thought I had answered that! sorry!

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Alright, I finally had the time to do a thorough examination, and found some interesting stuff. (i.e. I need help figuring out what the heck is going on.) It would appear that aside from calibration, the only differences in the OEM 2300 I'm messing w/ the idle circuit on an aftermarket 4-barrel are the things pictured below:



Yes, aside from calibration, the metering plates appear to be functionally identical. I'm sure that those reading (Argentina ) can tell immediatly what's going on in these photos, but I'll try to explain. The only difference I could find is that the hole I have labeled "b" goes straight through into the throat of the carb on the OEM carb, whereas on the aftermarket carb it goes down through "d" on the body and finally enters the throttle bore at "d" on the throttle body. (Aftermarket plate is on the left, OEM on the right)

The best I could figure out, gas comes in through port "a" on the metering plate and is mixed w/ air from port "b" before the whole mixture enters the bore through "c" on the throttle body. If this is the case, I don't understand how simply changing where the air intake is located will cause the idle screws to behave in a reversed fashion (i.e. rich is tight against the seat, and it gets leaner as you back it out). It looks like it would be possible to modify the OEM carb to be routed the same as the aftermarket, but I don't want to do that without knowing /why/ I'm doing it. Ya know? Any thoughts?

Edit: After googling for a while, I know understand that "b" and "d' are both idle feeds, while "c" is the transfer slot. Now my question becomes, does moving the idle feed to "b" cause the idle adj. screw to behave in a reverse fashion, or am I still missing something relatively major here?

Edit 2: After thinking about the situation more, it's beginning to make sense. W/ the standard arrangment, the idle orifice and transfer slot see approximately the same vacuum; therefore air/fuel mixture flows through the idle until the transfer slot is uncovered. With my smog carb, the "idle" port on the metering plate acts instead as an air bleed, since there is much stronger vacuum below the throttle blades than above. As a result, the closer to the seat the needle is, the less air there is drawn through it. On my carb all idle functions are actually handled by the transfer slot and the small orifice below it, which recieve the same mixture. That means plugging the "air bleed" (the port inside the throttle bores) and drilling out the passage for idle in the standard location will basically convert it to a standard carb in function, calibration issues not whithstanding. Sound right?

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

Since the Holley tech support was of little help (big surprise), I just wanted to check again w/ you guys. Does my final edit on the last post make sense?

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

hey cstriker

yes, your 2 edits are right on the money

I was writing a draft (have it saved) but you basically nailed it. Plug the B hole (the portion that taps into the barrels) and drill a small balance hole (1 mm) right on the bottom of the barrel on the carb's main body. Anyway, I wouldn't use the economaster metering plate...

will get back to you soon (tomorrow night or sunday morning)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Hate to resurrect a dead thread here, but I finally got the modifications done and installed. Initial impressions are that it worked great; tightening the idle screws all the way results in a stalled engine. It does have a bit of bog when you punch it that wasn't there with the old carb, but I'm tentatively blaming that on the accelerator pump.

The holes I drilled are a tad bigger than 1 mm though; the smallest drill bit I could find locally was 1/16, and even then they are drilled at a slight angle which makes the opening even larger. I'm guessing that's why I only need about 1.5 turns out on the adjustment to get max vacuum. (I thought it was usually supposed to be closer to 2.5?) All of this is using the metering plate from the 4-barrel.

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

yesterday I was thinking of this thread.

OK, you've done great so far. Try opening the needles to about 2 turns, don't worry if your vacuum reads lower, is kinda normal when you drill them blades... if your car really idles better with 1.5 turns and doesn't bog with 2 or 2.5 turns I'd place a restriction inside the idle discharge hole passage on the carb's main body, by means of tapping that hole and then use a small headless allen screw, drilled in the center to create a double idle restriction for the idle discharge hole and still be able to give extra fuel to the idle transfer slot by turning the needles over 2 turns open.

in your pictures, it would be the "B" hole on the carb main body, hat one needs to be tapped (4NF48? whatever you can find easily) and a corresponding size allen headless screw placed there after drilling the center off (be careful to leave the hex wrench socket intact) if you need the hole to be bigger than the hex wrench socket you might use a plain slotted headless screw (or be safe and use the slotted screw right from the beggining)

OR--

maybe you can jet down the carb and open the idle needles farther, if it doesn't affect power.

what size are you running now (jets?)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Right now I'm running 58 jets, iirc, which are probably a little bit large. This weekend I need to go out and do some cruising to get a good read on the plugs. I'll also try opening up the idle screws a bit like you suggested. I think I might also need to step down a bit on the power valve; it's currently an 8.5, and I'm pulling ~16 inches at idle.

Currently I get a good idle ~700rpm and don't have any problems other than this very slight bog. If anything, I think it's just getting a little bit too much fuel too fast from the accel pump (currently an orange cam in the #1 hole, iirc). You speak of drilling the throttle blades; currently, mine are solid. I have heard of people drilling them to get better idle with larger cams, but are there other reasons as well? I think I'm about to break down and go get some good reading material on Holley carbs. I understand the basics and can figure things out through trial and error, but this project is getting to the point that I can see myself getting in over my head unless I do some research.

Of course there's some other issues that need to be addressed before I go too gung-ho tuning on the carb. I really need to play with the advance curve, as I get slight pinging around 2000-3000 rpm. I'm also concerned I may have burned a few valves, as my vacuum reading constantly flutters about 2 or 3 inches (which it didn't used to do right after the engine was new). I need to get around to doing a compression check to see if that's gonna be an issue.

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

I did drill the throttle blades so I can open up the needles and have a very "wet", easy flowing transfer slot and yet keep the ability to kill the engine closing one needle. My slant is large cammed too (290º ballpark duration, stock lift, I get less vacuum at idle, 14-15"hg)

If you can kill the engine closing one needle I wouldn't drill them blades for now... also if you have a great accel pump shoot on the hi strenght signaled economaster, I can see a potential issue there... also is a matter of how much and when that extra gas streams shoots inside the venturis.

what kinda bog are we talking about? bog when accelerating hard off the line, bog when trying to inrease speed dramatically (hard acceleration when running low rpms to go high rpms fast? ) ??

maybe I'd go with 54 jets and still have that 8.5 power valve. What size of accel pump nozzle are you using? I run a custom #20 (small, but keeps the stream over a longer period of throttle opening) #56 jets and 8.5 power valve, I have drilled my blades 1/16" on each side and needles are opened 1.75 turns

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

the fluctuating vac rading can be due to some misadjusted valves too. let's hope you're good with them valves. Also, remember that big cams would render reduced comp check numbers... especially if you played around tightening the lash. I'd be satisfied with 120 lbs/sq inch (don't recall if I know your comp ratio, this would be with 8.something close to 9:1)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Yeah, the valves were adjusted at the last oil change (<500 miles ago). Didn't get around to doing anything serious with it this weekend, but I'm afraid I do have a few toasty valves. I had the manifolds off a while back and a few of the stems had a brownish tan look to them, whereas most of them were shiny silver.

The bog is hardly noticable, especially after things are warmed up. It's also only off the line, not when I'm already moving and try to accelerate. I'm running whatever shooter came stock on this carb (32, I believe?), but I think I've got a 25 I can swap in for experimental purposes.

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

Shooter size is fine at 31, I'll bet your pump cam is small and you have a 'short' shot...Some 2300's only come with a "red" cam...you might want to move up to something slightly bigger and see if it works better (orange)


-D.Idiot

DI, have you ever tried small shooters? like 20-22-25? I started to use them after I did the modification on the boosters (annular boosters, there are plenty of pics here) because of the better signal I got. No bogs and MPG went up a lot, and the smaller nozzle extends the shoot time and I think helps tu build pressure in less time when the arm hit the lever, so the shoot is strong even if you step on throttle lightly.

I'm just asking because the economaster boosters have way more signal than the original ones.

_________________
Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

After I do a cruise to check the main jets out, I'll probably step down to that 25 shooter. I believe the cam on there now used to be orange at one point in it's life (it's a little old). Unfortunately, progress over the next couple weeks is gonna be kinda slow, so don't expect any updates soon. (See my "It hates me" thread in "other" for details.)

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion