Change in direction w/ carburetor

This was supposed to be my "big" downleg option (1.58" venturi w/ Braswell downleg boosters), but it didn't have enough booster signal.

Now it's an annular...

You change out and flow your own booster Brad?

Why?? Too large

... a lot like my OTHER 1.58" venturi annular that's based on a QFT main body. Yeah, that's kind of redundant.

Funny thing is the airflow tests w/ the downleg and annular boosters were virtually indentical. I guess if you got a big enough hole to fill, the booster type doesn't mean as much re airflow potential.

It's been known to happen...

For my application, yes.

A smaller venturi with a decent downleg or stuffing annular boosters in the big venturi will respond better (60-ft., shift recovery).

Example of smaller-venturi downleg (1.50" v w/ Braswell boosters) that flows basically the same as that QFT 1.58" v annular above.

Ever heard the old expression: A man with one watch knows the time. A man with two never does.

In this case, it's probably: A man with one carburetor can find a good tune. A man with (uhhhh... how many do I still own now???) hasn't got a freakin' chance in He11.

I have no clue what you're even talking about, but thems some real pretty and shiny parts you got there, I tell you what

I got a booster shot once so I think I know what he is talking about.

It doesn’t seem so much of a change in direction as, “now I have two of these”.

Ummmm.... yeah... kind of looks that way...

And for some reason I feel like I need to ask my doctor about a booster shot.

Jeez-us, this sh!t is making me nutz.

if you got a big enough hole to fill, the booster type doesn't mean as much re airflow potential

I agree, it's the smaller primary venturis that are significantly obscured (lower CFM per square inch) by annulars, it evens out as the area goes up.
Why doesn't someone make s m a l l e r annulars? The usual stuff is cast, which requires wall thickness and internal strength at the cheapest cost.
Not enough sales volume. 3-D printing?

Shameless self-promotion: I "invented" adapting a Holley 4010 annular secondary booster to the 1933 Harley-Davidson 1 bbl. side-draft carb (Linkert Model M) used for 30 years.

http://www.victorylibrary.com/L-BK.htm

So then I want to ask the question are you better off with a bigger Venturi and a annular booster or keeping the Venturi a reasonable size for application and just use a good down leg?

Based upon everything I've read and heard from some pretty sharp people... it depends. Examples:

Annular boosters promote better atomizing of the air-fuel mixture, but they can work "too well" and result in less power, although improved efficiency. They're also more sensitive to temperature changes in the induction system. In certain applications they're more difficult to tune, such as large c.i. engines trying to run a 4150 annular and going rich early because the annular boosters come onto the main circuit faster.

Downlegs can be problematic when there isn't sufficient signal being made to pull the fuel through the booster and break up against the inside of the booster venturi. You can find some good videos of carburetor operation viewed from above the venturi and under these low-signal conditions the fuel comes out more like it's pouring from the end of a (very small) garden hose, barely touching the booster venturi.

Well, that's what (some of) "the experts" say. And then you look around at moden 4500-type carbs and rarely see anything but annular boosters... and the current lineup of Braswell 4150-type carbs doesn't appear to use anything but Braswell's design of downleg.

I cannot claim anything conclusive. Even if my future planned carb tests show an advantage of one approach over the other, that would only be valid for my specific combination & application.

Yep, that's a really long non-answer, but it's all I can offer at this point. Not having real test results sucks.

Google "mini annular booster" and you should see a link to the mini annulars that CCS has listed on eBarf. However, what I suspect with those is they are going to be fairly limited in fuel flow capability... and they look kind of crude IMO.

Thanks for the explanation. I figured it was going to be a testing deal. I guess my next question would be what led you to believe you didn't have enough booster gain.

I'm asking because I hope by the end of the year I can buy another flow bench (kicking my own ass on a regular basis for selling the last one I had...selling it was short sighted and ignorant but I've never claimed to be smarter than the average bear) and do some testing on my own. I think at this point I'm fighting a booster issue but I want to do a bit more work on my intake manifold before I proclaim I don't have enough booster gain.

The little bit of testing I've done seemed to indicate that annular boosters really help with cold air and/or a cold intake manifold. We saw some pretty impressive power gains on my 470 when running in cold air with an annular booster carb. Not sure that really helps though since most guys aren't racing or driving high perf cars when it is near freezing. Sure makes good power on the dyno though.

Funny you mention that. I drive my junk year round and I suspect the Strip Dominator and the down leg booster may be giving me issues. I've never had any icing issues and I've driven when it's been in the low teens.

My pilot training taught me a lot about air and how the weather affects it, cold dry air will make a hoop of power, hot humid air won't
When the first 830 CFM Holley annular double pumper carbs. first came out(mid 1980smaybe) nobody could stop them from going richer and richer above 5000 RPM
Almost every Dominator carb I've seen has annular boosters, some with skirts but most without
EFI doesn't have those issues

It could be helpful if you did some searching on the Racing Fuel Systems web forum, in particular for flow test vs booster signal data that Mark Whitener ('jmarkaudio')has posted there and on other web sites over the years.

Here's a LINK to one of the old posts on SpeedTalk where he provided information such as shown in the graph below:

I don’t think that’s the answer he was looking for

Those are all very nice however you may want to try a BLP main body from Dominic at Thumper carbs. You won't be disappointed. The BLP is the ultimate 4150 main body.

Such is life...

EDIT: Anyone who's willing to pay all my R&D bills can have all my R&D data.

I've asked for before & after test data on like-for-like venturi size & booster config comparing the BLP BX4 main body against the "traditional" HP-type 4150 main body, but have yet to see any.

I've seen the claims by the carb builders using that style of main body. It's pretty simple IMO: if they ET & MPH better than properly-tuned carbs of the same config that use HP-style main bodies, that would tell me there's something to the design.

Do they look cool? Yep.

Do they look like they "should" be an improvement vs the older style designs? Yep

Have I seen anything "real world" to justify making the switch? Still waiting...

David Vizard (first? 40 years ago) suggested that higher atomization (as produced by annular) increases the volume occupied by fuel, which reduces the air volume. High atomization is best in heads with excellent CFM capacity. If the head isn't that efficient, larger droplets (normal booster) means more air volume.
Mixture strength, air:fuel
By weight 14.7:1
By volume (fully vaporized) 9,400:1

An obvious try-out:
Annular for tip-in and part throttle response, and smaller HSAB to reduce the effect at higher RPM?

I'll agree with that.

I'm typically someone who has shared everything. However, for the latest carb "stuff", I'm still trying to figure things out and don't want to go into it publically any more than what I've posted.

No that helps. I forgot about that forum Brad pointed out. When I get some time I'll jump over there and spend some time reading.

Thanks Brad. I never expect anyone to give it all up for nothing.

Eventually, for better or worse, all the juicy (or gory) details will most likely come out.

Right now there are too many variables in play that I won't understood better until I can test the carbs on my car... which isn't running, yet.

I'm stuck with a bunch of hypotheses in the meantime, and my hypothesis "hit rate" might be about 50%, if I'm lucky.

FWIW, here's my baseline, a late-90's BG Gold Claw 1.425" v that's proved to be a nice balance between streetability and on-track performance.

OK... I didn't mention I had it wet-flow te$ted.

Here's one of those things for which I may never have an answer: If the BLP 1.59" v BX4 body on the left was fitted with the same annular boosters as the modified Holley Ultra 1.58" v body on the right, would the difference in the main body design itself result in a quantifiable improvement?

Just looking at them I would have to say yes. There are no interruptions (besides the boosters) in the bores to the left where the Holley looks like a yard sale on the top of it. Left also looks like a smoother transition from the booster to the plate. The throttle plate itself looks to have blind screws.

I have the same BX4 main body with down leg boosters on my pump gas 434 small block and have wondered if annulars would be better for my street/strip use.

My carb started as a Bigs 950HP, if I can come up with a four corner idle 1 3/4" base plate I'm thinking about building the 950 to test at the strip against the BX4.

It should look familiar... that's a picture that you posted which I cropped to show only the BLP body.

What about these two 1.58" v HP-style bodies that both have .600" ID 12-hole annular boosters? Do you see 20 CFM difference in flow between them?

You dog! lol

Throttle plate? Screws? On the left?

It looks more like a main body sitting on a table to me.

I’m sure Summit will happily take your cc number and send you something suitable.

Nice table cloth!

Yeah, ain't nuthin' but a bare body shown for the BLP.

Funny thing... what Bigs calls a "950" uses the 1.40" venturi main body that QFT/Proform call an "850".

The QFT/Proform "950" has a 1.45" venturi, along w/ stepped downleg boosters, rather than non-stepped downlegs their "850" uses.

It seems the number is marketing hoo-ha?

Hijack: Would you happen to know of any reason I can't put Proform or QFT metering blocks on my old "1000" (?) Race Demon? The way the bowl sort of wraps around the stock metering blocks makes me question it some. I'd like to get a better tune happening on it as soon as I get some more test time with the QFT Brawler 950.

Haha! I looked at it at least twice too!

If I had to guess the right one flows better. I know nothing about it (obviously) so I have to go with my eye which sees invisible throttle plates!

I'm just gonna say now my bet is the 1.425" v is gonna perform at the track.

Looks like you have already made a MASSAVE investment in cast 4150 carbs and parts. At this point why wait for someone to post results on the capabilities of a BLP main body when you can simply buy one and try it out???

The ol' Gold Claw has worked well, once the original (horrible) BG tune was corrected. But I've seen it give up 10 HP and comparable torque to Dwayne's old-school CFS-modified Holley 850 annular. I'm hoping that somewhere in this pile of shiny sh!t there's another carb that will do better, which is why the GC is still the baseline.

It would be nice if someone else had spent the $$$ already for the parts & tuning time, instead of leaving me to do it only to find out that looks ain't everything!

I had a old 850 annular that drove great around the pits and I thought ran pretty good on the track. Put a small 950hp on it and went a tenth quicker. Mostly due to shift recovery.
Both were out of the box though so I'm kinda interested in your results.

What kind of $$$ are we talking for one of those BLP bodies?

Bare uncoated BX4 body $208 (no boosters)
Coated version for $226
+ cost of boosters... maybe $40 for banjos & $50 for billet inserts
+ cost of installation (requires some special adapter that the standard booster installation tool doesn't come with, IIRC)

I dunno... maybe $350+ ?

Okay....... so not crazy money.

So is the Challenger running again?

Still ...

No, but not a priority, either. I have other things to spend the $ on at this time.

I wasn’t suggesting you buy one....... I was really just curious about the cost.

Just buy a BLP main body and get er done!! Sell one of those dinosaur carbs on Craigslist to recoop your $$$$. This will end the debate and you finally be able to sleep. I really like mine!!!!!!!!

$256 uncoated with boosters, air bleeds and squirters.

https://blp.com/cart/index.php?main_page=product_info&cPath=65_397&products_id=1601

The BLP BX4 and Bigs HP bodies.

If someone is considering the BLP BX4 main body be aware that Holley air bleeds won't work in them unless they are turned down. I made a fixture to use in my lathe out of a piece of 3/4" aluminum round stock.

When I bought my body there was nothing in the description about the difference in the bleeds. When I received mine I was somewhat pi$$ed that my bleeds wouldn't work. The guys BLP stepped up and sent me what I needed and now there is a note at the bottom of the web page noting that BLP bleeds are needed.

Have you ever back-to-backed the two, either on the dyno or at the track?

Shiny or not, all carbs are dinosaurs compared to a good EFI system.

Like The Haze?

No, I used the base plate, metering blocks and bowls off the 950 on the new BLP main body. I have everything but the base plate to build the 950 and I think I still have my notes from the dyno to set it up by. If I come up with a base plate I'll do back to back test at the drag strip. I'm thinking of selling my car so it may not happen.

When you dynoed the motor which carb body did you use?

Selling the car?
Going late model?

Not hardly. We were told that lie about PS. A good carb is hard to beat.

Naaaahhhh... Last I heard, The Haze was sleeping in darkness, or something like that. The MoPig's in a perfectly well-lit garage gathering dust between infrequent wrenching sessions.

I really like my BG Gold Claw, too. And Dwayne's not-a-spec-of-billet CFS-modified original 4781 850 dp made 10 HP more and better torque across the RPM range than the BG when we tested both of them. That's not even using an HP-style main body.

Like I said previously, the BX4 bodies LOOK like they should work better, but that's no guaranty it'll show up on my ET slip. Therefore, trying a billet main body is a wait & see thing and may not ever happen.

It was dynoed with the 950HP.

I'm thinking about selling the Dart and buying a newish Challenger, low mile Hellcats can be had in the 48-50K range around here.

Or sell the Dart and build my 65 Dart to run some street car stuff that's popular around here. The 69 is not going to get cut up but it wouldn't bother me to strip/cut the 65. It would be ugly, but it would also be light and light cars are easier to make fast.