Annular Booster Quandary

[289nate]

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

750 version says it’s out of stock. Wonder how long it would take to get one. Hope it’s not anything like the intake manifolds.

[RevTheory]

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.

What booster style were you running when you did your open vs. tapered spacer test?

[skinny z]

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.

Interesting to know. One racer I've chatted with has these designs on the Air Gap.

Air Gap Mods.jpg

Quoted. "When I modify those Intake Manifolds...
I TIG weld the HVH Spacer to the Manifold, and re-shape, contour, port, and blend the Plenum opening and Spacer into one uniform opening.
The material/ areas that have Black Lines outlined, are removed and re-shaped to be more like a Single Plain opening."

ported HVH Spacer.jpg

The taller Manifold/ larger Plenum area, with the transition from the ported HVH Spacer into the ported shared Plenum space...
along with some Runner transition porting, and Port-Matching... really improve the already great performance of the Intake Manifold.


I'll undoubtedly start a new thread to discuss this further when I'm at that point.

[skinny z]

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.

Also interesting to know.
I've a Barry Grant 1402020VE which has been an excellent all round carb for the street and strip. The goofy choke mechanism not withstanding.
Easy to tune on a worn out 355 with 71 degrees of overlap and about 10.2:1 CR.

Spec sheet.docx

That said, I was going through a high speed lean out at the top end and never got the opportunity to investigate what the issue was. I was dealing with a myriad of problems getting the car dialed in generally speaking.
I'd like to know more about the small primary side tube pick up mod.

[C.A.R.E.]

408swinger : they now say first of March ! I’ve heard that before.

[skinny z]

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

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

750 version says it’s out of stock. Wonder how long it would take to get one. Hope it’s not anything like the intake manifolds.

408swinger : they now say first of March ! I’ve heard that before.

None of what I've read in their spec blurbs refers to the booster style.

[RevTheory]

Wilson Manifolds was pushing their tapered spacers on Facecrook so I asked them if I'd made a mistake buying a 2-incher for my 5,500 peak hp rpm 383 with an RPM Air Gap and a 750 with annular boosters and the reply was "most people buy all three sizes and test them at the track"

I reached out to Mark Whitener (sp?) and he said most-definitely annular boosters with the right body but he's two months out to build anything for me. I asked The Carb Shop about building one and they don't recommend annular boosters; "too much signal."

This is turning into a much bigger pain in the ass than I'd anticipated as I simply do not have $2,500+ for a carb with downlegs, one with annulars, three expensive spacers and the dyno time required to just sort out that one part of the deal.

I know at some point, it is what it is but I'd really like to tighten up the window a little bit.

[skinny z]

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?

Does it have to be one or the other? As in a vacuum secondary with annular boosters? That would be the BG I have.
And the question begs to be asked: What does DV have to say? I'll bet annular booster all the way too.

...a carb with downlegs, one with annulars, three expensive spacers and the dyno time required to just sort out that one part of the deal.

It seems to me that some dyno shops would have those items on hand for testing. The time to do the testing is another matter.

[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?

Does it have to be one or the other? As in a vacuum secondary with annular boosters? That would be the BG I have.
And the question begs to be asked: What does DV have to say? I'll bet annular booster all the way too.

...a carb with downlegs, one with annulars, three expensive spacers and the dyno time required to just sort out that one part of the deal.

It seems to me that some dyno shops would have those items on hand for testing. The time to do the testing is another matter.

BG apparently dropped that line; vs with annulars. After doing some research, it doesn't appear that Holley tech (ha!) even knows much about Demon carbs anyway so I've likely opted out of that line.

I've probably made too much out of this. Unless I'm all fuggered up, the "problem" with increasing plenum volume is booster signal. I can't see booster signal being a problem with a tapered spacer and annulars. None of the tests I've seen have touched booster style when doing a shootout on 1-inch vs 1.5-inch vs 2-inch. That just says "inconclusive" to me.

And I'd certainly like to think that the dyno shop has his favorite carb and a rack of spacers. Maybe I can get out of my own way long enough to call Pro Systems or someone similar and asking their thoughts rather than getting frustrated and just ordering a QF 750 from Summit and then spending countless hours questioning myself

[skinny z]

....spending countless hours questioning myself

Yep. I'm familiar with the feeling.
The flip side to that has been described to me as analysis paralysis.
Then again, the virtual engine building I've been doing while waiting for the COVID rebound to fully kick in allows me to do just that. But there's no substitute for the real thing. Can't wait for some dyno and track time myself.

[1972ho]

I also had the carb shop tell me and then modified my annular booster to down leg.But I bought another one a 850 and had the same problem with its rich condition so I bought a set BLP metering blocks for it and started tuning it and got to lean out and run like it should.You can do it you just have to make it work.Plus the carburetor shop modifications made my carburetor lean after they made changes to it.

[ChopperScott]

Wilson Manifolds was pushing their tapered spacers on Facecrook so I asked them if I'd made a mistake buying a 2-incher for my 5,500 peak hp rpm 383 with an RPM Air Gap and a 750 with annular boosters and the reply was "most people buy all three sizes and test them at the track"

Without real world testing on your combination, it's just a guess. Even a dyno proven combo may not be optimal for the track.

[GARY C]

Would annular be the best choice for a heat soaked street intake?

[ClassAct]

Would annular be the best choice for a heat soaked street intake?

No. But of you can keep the engine temp between 160-170 and use a cold air intake you can easily run AB’s. Or get a big enough carb so it needs them.

[RevTheory]

Would annular be the best choice for a heat soaked street intake?

No. But of you can keep the engine temp between 160-170 and use a cold air intake you can easily run AB’s. Or get a big enough carb so it needs them.

I'm hoping for no more than 180* in the summer with a ram air box and cowl-induction hood.

No drier vents this time around, lol

Blazer 1.jpg