Annular Booster Quandary

[RevTheory]

I can't seem to make a decision fellas so I'm hoping you guys can provide some direction here. 750 vacuum secondary with downlegs or mechanical secondary with annulars? Barry Grant Speed Demon but I'm not committed. I tend to think that most new carbs are over-emulsified with 5 bleeds and the Demon only has 3 but who knows. I could be in left field on that, too.

The engine in question is a 383 SBC:
10.35:1
DART SHP 180 heads. Probably pour somewhere around 185cc when done
Bullet hyd/roller 277/281 adv. 223/227 at .050, .580/.552 lift with 1.6/1.52 rockers, 107 +4
Doug's tri-y headers
Performer RPM Air Gap with a 2-inch Wilson tapered spacer

83 Chevy 4x4 truck
700r4 "Mega Raptor" from transmissioncenter.net with a 2,500 convertor that I can manually lock up from 2nd on.
35x13.5 tires
4.56 gears although I could possibly talk myself into 4.88s. 2,460 rpm locked-up at 75 mph doesn't sound terrible.

The truck will get retro a/c here in a few months and I'm not sure Demon has a fast-idle solenoid so that may change my mind on brand. I'm not real sure how much a compressor will drag the idle down. I'm going to relocate the IFRs to the bottom so please refresh my memory on the bit and tap size. I'm just bouncing back and forth on booster signal and can't seem to land anywhere.

Any thoughts?

[n2omike]

A always like mechanical secondaries. Annular boosters are good, but keep in mind that they need a larger venturi than a down-leg, as they take up more room and are more restrictive. Others may give you more specifics and detail.

[BOOT]

I like annular for a cruiser(Street/Strip)

Just from googling a pic of the demon blocks they remind me of the 3e hole QF blocks and I didn't like them. It's not so much the 5 or 3 holes(you don't gotta use em all) it's more the overall design of the metering blocks that is better in my opinion based on what I've been told & read.

On another note I'd leave the spacer off, again in my opinion Tapered spacers are more of a WOT gain and a 2" is basically 1" of open, that may hurt drive-ability. So depending on your use and from the retro AC sounds more like a street machine. May be fine with the spacer but if it isn't, it would be the first thing I'd take off.

[In-Tech]

Annular every time, changes the fuel curve dramatically. Have good data acquisition(at least 25hz) and expect plenty of hsab. Having 5 emulsions just means more adjustability, don't be afraid to plug a couple.

[1980RS]

I can tell you from experience that the Air Gap will not like the 4 holed tapered spacer as it slowed my car down with it. The 1" open spacer worked great though. As for A/D boosters vs down legs for me it's a toss up as I have run both and have had great results with both. This past year the down legs were better on my pump gas 358 SBC and the winner was my vs FST 850 down leg booster carb. You just have to test them. I know one thing for sure, late in 2020 I tested a BG vs A/D 750 and it was a complete dog and slow as all heck. Turned out the sec side was not opening at all, I fixed that by adding the small pri side tube pick up mod and re-tested it out this spring results, it was a tenth and 1 1/2 mph slower than my 1000 Mighty Demon. Still pretty good compared to what it ran prior.

[HQM383]

Annulars tend to give more low to midrange torque, good for a 4x4.

Tap is a 6-32 for the IFR and emulsion bleeds.

6-32 NC: drill size #35, closest fraction 7/64", decimal inches 0.110, metric drill 2.8mm

If Holley have not changed the metering block from the Barry Grant days then the emulsion is easy to tap for screw in emulsion. Just open up the pre-drilled emulsion hole at the bottom to .050”+ and then run the 6-32 tap down the opening. Using set screws for emulsion then set a depth to tap. Using headed emulsion follow up with a 4mm drill setting the depth the height of the head.

[tuffxf]

G,day,
IMHO which is not worth much, in your application would be very hard to go past an old 3310 or 3310-1, you can still find them, they work very well, they are not messed up like the new stuff.
The emulsion works well, secondary activation works properly and is easily tuned.
They don’t look as flash as the new stuff but!
Cheers

[swampbuggy]

G,day,
IMHO which is not worth much, in your application would be very hard to go past an old 3310 or 3310-1, you can still find them, they work very well, they are not messed up like the new stuff.
The emulsion works well, secondary activation works properly and is easily tuned.
They don’t look as flash as the new stuff but!
Cheers

[Geoff2]

Edel 800 AVS2. Primaries have annular boosters.

[1980RS]

Edel 800 AVS2. Primaries have annular boosters.

I got my hands on one of those dirt cheap last year, the guy I got it form hated the carb and switched to FI. That's ok, $100 is a lot less than what I would have paid for it form Summit.

[RevTheory]

Who builds killer custom carbs for hot, street use where a choke is required? There are too many to choose from based on a website.

[Geoff2]

Edelbrock.

[Walter R. Malik]

The "pullover" point is different and "signal depression" curves are almost exactly opposite from one another.

[408swinger]

This is where I think the new Eddie 4150 will be the hot ticket . If they ever release it ....

[BOOT]

Interesting didn't know eddy had a new 4150 carb, looks like they changed a lot up. https://www.edelbrock.com/catalogsearch ... carburetor