Jay's dyno testing with carbs (question for Jay)

[Falcon67]

I don't know that you need to get that fancy with the annuals.  I have a lot of gear and converter, but I'd expect the 600s to be just as good with a 3000+ and 3.73~4.11 type gearing.  On the tunnel ram, you could figure you're running 4 cylinders with a 300 CFM two barrel, which seems way less exotic than 1200 CFM of carbs, when you break it down.  My 351C makes around 450ish HP in the current configuration. 

When I put the tunnel ram and dual Edelbrock 1406s on the 302, the drag strip 60' only dropped maybe .05~.1, if that.  It still hit the tires hard enough to pop the fronts up a couple of inches.  I might have brought that back with a bit more pump shot.  Maybe not, the primaries on the Eds are very efficient but don't flow so much IMHO - they are a bit like a mini-spreadbore carb.  I also ran that same engine with a 600DP, 650DP and even tested a "750DP" with a ProForm body and QFT blocks - all on an Air Gap and all performed about the same.  MPH always within a buck or so.

[FElony]

Not sure what your Cleveland race car has to do with my question. Anyone else care to ponder outside the box?

[Falcon67]

Not sure what your Cleveland race car has to do with my question. Anyone else care to ponder outside the box?

>What about, at 400-450 street hp, a pair of 4180 annulars for manners?
Carbs don't car which motor is under them.  Smokey always said an engine doesn't know what name is on the valve cover.  Annulars tend to go fat at higher RPM.  They do help at low RPM with tall gears, tight converter, heavy car because the will atomize fuel better than the standard dog leg Holley booster.  Whether it matters depends on the whole combination.  Also, the T-ram on the 302 using dual 600 Eds made maybe 300 HP in good air, so HP of the combo may not be the primary deciding factor.  Intake design and velocity matter.  The OP asked about 450s - those are mechanical secondary carbs with only a primary accelerator pump - IMHO they would suck trying to tune for anything other than a street/strip car with lower gears/higher stall.  People run them and like them, bit of a mystery to me.

[gt350hr]

Sorry for the 2nd post on this,  but.
I was amazed 50 years ago at what Smokey was doing but that thing he dreamed up is unbelievable now and that was a long time ago.

       Are you speaking of his "variable runner length" Boss 302 dual dominator intake?  It didn't work. The plenum area was TOO big for two dominators. Yes the T/A engines in '69 ran them but they were designed to be used like a Weber where each venturi fed "one" port only , not a giant plenum.

[CaptCobrajet]

The little carbs will usually run into fuel curve problems as power level increases.  Dale touched on power potential with OE carbs, as in Stock and Super Stock apps.  You can milk lots of power from OE carbs, but it becomes a science to keep the curve nice in the band that you are trying to run in.

I have done a ton of 2x4 tunnel wedge engines in the last ten years.  Booster signal and management of the curve ends up being the focus to make power and run smoothly.  An unhappy carb(s) will make the engine surge through a loaded pull.  The dyno software usually "smooths" the surging, but screwy break specifics and lambda A/F numbers will still remain.

Drew is making some hints and speculations that would prove out if he did get to test his ideas.  I think that less than 600 cfm carbs is a waste of time.  If one thinks they might be "too much", use vacuum secs and play with the opening rate.  Smooth but quick opening will always feel better and make more power, even on smaller engines.  We do a bunch of 4160 style carbs for the big strokers.  Some approach 1000 cfm each.  It takes a healthy big engine, like 900+ hp to really benefit from big venturi carbs.  Hard to beat a good working pair of 660s.  They get fussy around 800 hp and need fuel curve tuning.  As power increases, the 850s or more modified main bodies become easier to tune.

Small venturi, like 1.320, with a 1-11/16 throttle bore, are usually super good for 650 to 800 hp streetable and raceable engines.  We pick a venturi size and throttle bore based on past experience, and then find main bodies that can get there.  Custom tapered end mills, and radius-entry or straight taper entry custom end mills are used to get where we want to go.  My man simulates booster signal and tunes the boosters to fit what we anticipate we will see.  High speed, emulsion, and transition tuning all come into play.

If I were you Ross, taking a stab without much history to look at on what you describe, I would get a couple of main bodies around 1.250 to 1.313 venturi, and re taper the bottom to accept a 1-11/16 baseplate.  Depending on engine size and power level, you may have to add some emulsion and go up on the high speed bleeds......maybe, maybe not.  The transition bleeds are a driveability deal, and it can be done with a manual load dyno so you can simulate some driving conditions.  Takes a lot of time.......

[Drew Pojedinec]

Drew is making some hints and speculations that would prove out if he did get to test his ideas.

Along that line....  a disclaimer for anyone that takes what I say as fact.  I'm an engineer that can prove my theories with math, but ultimately I am just a dude with a car that doesn't get to drive enough to do as much R&D as I should.  Sometimes I get enough feedback from customers to be able to adjust or massage my views. 

Nothing can beat the experience that Barry, Brent, Blair, have in regards to hard fact dyno and race track numbers.

[My427stang]

Don’t anyone get concerned, not my first rodeo, or even 10th with dual quads. I was only looking for Jay’s  chart...we have a plan to test the carbs, with four more to bolt on after the 465s, and yes I agree with you Blair, expect the engine to pull real hard on the top of the curve. I will share the results.

BTW I agree with all of you, and appreciate it, but we will see if the dyno justifies the price of two new carbs. In the end, everyone has a cost/benefit line

Thanks!

[Barry_R]

The guys I worked with at Holley hated the old mechanical secondary, no pump 450s - called them "flamethrowers". 

You can have a fair amount of fun working carbs.  As Blair noted, a small, restrictive carb will tend to roll rich as airflow increases up to the point where the booster goes "sonic" and everything goes wonky.  Some pretty sharp guys will work hard on optimizing vertical booster placement within the man venturi, and reducing booster cross section both in height and diameter to get where they want to go.

Annular boosters work really well at a couple things.  They generate a really strong signal, tend to "start" early in the curve, and they atomize well.  Historically they were used with 'oversized" carbs to soften their inherent negative low end/midrange issues.  The downsides to annulars were flow reduction due to their big cross section, and a tendency to roll really rich at high speeds due to the strong signal.  I've recently seen some pretty serious carb efforts with what were essentially micro-annular boosters - cross sections nearly as small as a normal downleg, and with about eighty four million very small discharge holes (actual hole count is different, but you get the idea).

The large throttle plate couple with a small venturi was an old drag racer/oval track racer trick back in the proverbial day.  The standard 4150 race carb of the era was a Holley 750 with an 850 base and some blending.  Might have been a Braswell deal (he did and continues to do a lot of really cool carb stuff).  Holley used this platform, along with Braswell consultation as the basis for the first of the HP series carbs in the late '80's/early '90's.  The marketing guys bowed to marketplace pressures and decided to refer to it as a 950HP, although actual airflow was closer to 830 cfm.  It was and is a damn good carb.

The 4180 Holley was an OE carb for various Ford trucks and the 1985 Mustang GT.  It had a bunch of really interesting features, and I was always surprised that it never caught on in the aftermarket.  Annular front boosters and normal rears, the accelerator pump bleed hole to reduce pullover and pump well boil out, and a couple other things.  Two of those might work pretty darn well on a dual quad 445...

[Drew Pojedinec]

Annular front boosters and normal rears.  Two of those might work pretty darn well on a dual quad 445...

That is an absurd idea sir.....    What kinda person would take a 3310-2, knock the boosters out, install annulars in the primary, stepped downlegs in the secondary and put those on his car?
With the massive Dove removable top TW it makes low throttle input/cruise pretty sporty.

IMG_4706 by Drew Pojedinec, on Flickr

IMG_4624 by Drew Pojedinec, on Flickr

[gt350hr]

   I like the 660 base plate on the carb closest to the camera.

[Drew Pojedinec]

Yeah, I just plug any vac areas on those, I like them too as they seem stouter. I like using the stock type baseplate for secondary carb so no linkage needs clearance.

[Falcon67]

Annular boosters work really well at a couple things.  They generate a really strong signal, tend to "start" early in the curve, and they atomize well.  Historically they were used with 'oversized" carbs to soften their inherent negative low end/midrange issues.  The downsides to annulars were flow reduction due to their big cross section, and a tendency to roll really rich at high speeds due to the strong signal.  I've recently seen some pretty serious carb efforts with what were essentially micro-annular boosters - cross sections nearly as small as a normal downleg, and with about eighty four million very small discharge holes (actual hole count is different, but you get the idea).

Why I ran a Holley 84011 for a while - what is now the Summit carb 750.  Uses a front (and rear) annular venturi assembly very similar to the Ford 4100.  Uses all other Holley parts - jets, vacuum diaphragms, accel pump parts, etc.  I used that on a mild 351C street engine, 11" converter, 3.23 gear but with a big Weiand single plane on the engine.  Great carb, still sitting up on the cabinet with a bunch of other spare carbs.  Drove nice, no hesitation on street or track.  I quit using it because Holley discontinued the 4010/4011 line and parts dried up - specifically the booster unit, which you had to drill to tune pump shot.  Now that Summit sells the carbs, might be good again on the right motor.  I wonder if they have a better time moving the carbs - Holley I think had sales trouble because "that don't look like no Holley I seen". 

The large throttle plate couple with a small venturi was an old drag racer/oval track racer trick back in the proverbial day.  The standard 4150 race carb of the era was a Holley 750 with an 850 base and some blending.  Might have been a Braswell deal (he did and continues to do a lot of really cool carb stuff).  Holley used this platform, along with Braswell consultation as the basis for the first of the HP series carbs in the late '80's/early '90's.  The marketing guys bowed to marketplace pressures and decided to refer to it as a 950HP, although actual airflow was closer to 830 cfm.  It was and is a damn good carb.

I've read somewhere a flow test on the ProForm main bodies (an independent test, not the mfg) using the billet base plate - the same 830 flow number was mentioned.  Stands to reason since it's a knock off. 

See whacha think of this LOL

[frnkeore]

Speaking of 4100's, has anyone worked with those, either single or dual?

I shunned them, over Holleys, "in the day" but, they seem to have some attributes with weight and those boosters.

[Falcon67]

4100s are great - good luck finding decent ones for any reasonable price.  "back in the day"  i put a cast iron 4bbl intake from the wrecking yard on my C code 289 (2bbl), tube headers and a 1.12 4100.  And aluminum M/T valve covers, plus a 14" air cleaner.  Car (4 door Falcon with complete interior, all steel, etc) weighed probably 3400 lbs at that time. With a RAN 3 speed and a 2.79 rear end, F60-14 tires it ran 14.6 @ 96 MPH at Green Valley. 

[frnkeore]

I have 3, complete, good ones (all 600 cfm 1.12's) and maybe one or two others. Plus a couple of 2100, 1.14, two barrels. They also made a 1.19 (670 cfm) 4v and a 1.33, 2v but, I don't have any of those.

Like I said, I didn't use them, in the 60's and early 70's but, in the last 10 years, I've heard good things about them. They put them on a lot of Fords, in those days.