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Single 4bbl verses multi carbs

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pmuller9
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Re: Single 4bbl verses multi carbs

Post #51 by pmuller9 » Fri Sep 18, 2020 8:53 pm

Start with this book.
These folk do a lot of work with the Megasquirt systems and their user applications so the book will contain a lot of useful info.
https://www.diyautotune.com/product/per ... gJ4MfD_BwE

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Re: Single 4bbl verses multi carbs

Post #52 by Red rose racer » Sat Sep 19, 2020 9:34 pm

I looked at this plenum again, ford makes throttle body’s that mount up , mustang for sure have them and like Holly sniper, is suspose to be easy to work with and self learning and controllable. I am getting real exited about this setup.

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Re: Single 4bbl verses multi carbs

Post #53 by pmuller9 » Sat Sep 19, 2020 10:03 pm

Red rose racer wrote:I looked at this plenum again, ford makes throttle body’s that mount up , mustang for sure have them and like Holly sniper, is suspose to be easy to work with and self learning and controllable. I am getting real exited about this setup.

Which plenum are you referring to?

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Re: Single 4bbl verses multi carbs

Post #54 by Red rose racer » Sun Sep 20, 2020 10:25 am

The plenum pic you sent but ,meaning the mounting surface for the throttle body. I,m getting way ahead of myself, I have a lot of work to do before I should be considering lnduction systems. Sorry, I,m trying to organize a plan of attack. I understand the one in pic. Don’t fit I 6.

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Re: Single 4bbl verses multi carbs

Post #55 by pmuller9 » Sun Sep 20, 2020 1:24 pm

I'm just checking to make sure we are both on the same page.
The plenum design I posted is strictly for individual port injection with six injectors and not for throttle body injection.

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Re: Single 4bbl verses multi carbs

Post #56 by pmuller9 » Sun Sep 20, 2020 8:23 pm

Red rose racer wrote:Pmuller9 your susgestion of 12 to 1 compression ,how will E85 handle that high compression. And roughly how big a cam lift.

I've been thinking about the extra work and expense to make a 12:1 compression piston and I'm going to change my recommendation.
Using the 300 large chamber head which will be needed later for turbocharging, a flat top piston will give you a 10.5 to 10.7 compression ratio.
The flat top piston is less expensive and lighter than a dome piston plus you don't have to worry about valve clearance.
The power difference between a 10.7 and 12.0 compression 300 six is not enough for the trouble of making a dome piston.

This also makes fuel octane much less of a concern.

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Re: Single 4bbl verses multi carbs

Post #57 by THE FRENCHTOWN FLYER » Sun Sep 20, 2020 10:25 pm

Red rose racer wrote:... You said bottom standard injection tubes are to small, how much bigger would tubes have to be...

Ideally, for an IR around 58 mm, tapering to as big a port as you can get in there.
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Re: Single 4bbl verses multi carbs

Post #58 by Red rose racer » Mon Sep 21, 2020 9:52 pm

I would have done the 12 to 1 comp. but I must say I would have been a little bit uneasy about it. My last BB521 went Bang after one season . It was ARP studded running 14 to 1 with my special mixed fuel and being the only full body In the dragster class, that s the only way I could keep up with them , and I did.

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Re: Single 4bbl verses multi carbs

Post #59 by Red rose racer » Wed Sep 23, 2020 6:19 pm

I just received my 2 new books. Performance fuel injection systems, Matt Cramer and Jerry Hoffman . port& flow test cylinder head , David Vizard, had some of his other books, very informative. I will be busy the next couple of weeks

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Re: Single 4bbl verses multi carbs

Post #60 by xctasy » Wed Sep 23, 2020 9:52 pm

Red rose racer wrote:Have the 4bbs manifolds come so far , why are they used more than the multiple carb manifolds, like 2x2 or 2x4 or 3 singles ,even 6 in a row , one per cylinder. With the computer controled engines of today why not more.


Weber master Pat Braden in his 176 page HP Book Weber Carburetors says

1) engines with multiple divorced throttle bodies and carbs need a very bulky intermediate shaft to unload the throttle from any non linear forces.

2) Port on Port, Isolated Runner and Independent throttle systems (like Cobra Daytona's, 289 GT40'S, Halls US Pantera GT5's et all)
, each require
a) very high quality intakes and throttle balance that is not upset by internal signals,
b) that can be independently balanced using either a common vacuum balance line, or by individual vacuum sychro-testing that
c) doesn't influence the curb or wide open throttle angle during synchronization.

Everything has to be perfect, and that costs big bickies.

3) The use of power valves is generally a crutch to supply fuel under a low vacuum situation. 4 and 2-bbl Holley carbs reworked for In Port on Port, Isolated Runner and Independent throttle systems, often require power valve elimination and an intermediate circuit like a Weber , Edlebrock or TMP Power Plate. In most cases, its considered easier to ignore a, b and c, and move away from simultaneous operation, and go back to the Offenhauser Ford 144-250, 340/440 Six Pack or J2 Oldsmobile or 389-421 GTO Tri-power center on, outer secondary system. Power valves, vac secondary or mech outer operation avoids the need to add an intermediate shaft, and allows the center carb to operate kickdown linkages and most of the idle can still be six cornered with the outer carbs still supplying fuel at idle to keep fuel fresh.

4) With Port on Port (POP), Isolated Runner (IR) and Independent throttle (ITB)systems the flow speed is simply massively dropped from 265 feet per second on some 4-bbls to less than 18 feet per second in some 6-bbl cases. They are designed to stall air speed so each venturi and pulse tune like an alternating current, sometimes creating a romantic fuel standoff situation which also requires expensive flame arresting air cleaners and elaborate methods to contain the haze of gasoline so the aromatic hydrocarbons don't go on fire.

5) Carb sizing goes haywire based on the idealized 400- 1000 cc cylinders our over 3 liter sixes and 500 cube Cadillacs have. When Isolated Runner, If the carb venturi's don't supply air for the sweet spot rpm where maximum power occurs, the power band goes into a unstable zone where extra revs fail to give extra power. It can even nose dive where the engine has a cyclic power wave which an engine or chassis dyno operator will mistake for spring surge. Going up in venturi size is massively expensive because six throttle bodies then need to be upsized.


Image

For an engine with 819 cc per cylinder, you have to extrapolate the target ventri diameter in mm and source a relevant carb.

Image


See viewtopic.php?t=77685

Even below 500 hp, Cotton Perry and the late Jim Hedrick found out that IDA 48 Weber 2-bbls had restrictions in terms of total venturi area.

After 1978, In terms of net venturi area to support an independent runner intake, they found it was its pretty hard to beat this for a 292-300-310 cubic inch in line six


Image


Above you are three 780 or 800 cfm carbs. (Not installed from the factory, but available as an "over the counter" service item only, the 1968 -1969 Holley 4bbl Camaro 302 Dual Quads List #'Numbers replacement #4210 or new ex dealer # 4053 or #4295)


For the Chevy II with its 292, they were used to get the rev range into the usefull 7000 to sometimes 10000 rpm bracket. Three Holley 4-bbl 4150 PN 3923289 DZ Holley # 4053 PN 3957859 Holley # 4295 carbs were based on the old 396 350-375 or 427-430 hp and similar to the later 290 hp Boss 302/390 FE pr GTHO 351 Phase III carbs.Those all have a ventrui area of about 3.108 sq in per two barrels. That's the same as One 2" venturi, and supports about 650 hp at 8400 rpm for approximately 820 cc per cylinder on a 300 cube six.



See https://www.12bolt.com/cotton-perry.html



On barrel of a ID 48 has a nominal venturi of about 42-44 mm, so a 43 mm venturi is 2.25 sq inches. A 600 4-bbl Holley, or a 660 center squirter 4-bbl has 2.58 sq inches per 2-bbl, or 5.16 sq inches total from Table J, total Venturi area.


That's about right for a 300 six reving to 5500 rpm.


The idealized Weber IR curves are still the optimum,, but as stated before, you can grab three 4-bbl carbs, and phase each 2-bbl to equal the total venturi area of a bigger Weber DCO or IDA/IDF carb without the expense.

Best bet are 1:1 linkages for secondary operation, and conversion to Four coner idle, but 4-bbls pulse tune just like a Weber if the net venturi area is matched to the peak power rpm level.


"Pulse tuning" for carbs only happens at about 11 to 18 feet per second of air flow, so you have to go big. Forget all that CFM flow rate hocus pocus. Only focus on the ventrui area required to match the peak power rpm. Then engine will rev above the peak power rpm. 5500 rpm is a good figure to punt for.

Your limit is the space under the hood, and the proximity to the spring tower braces or spring towers if its an XK 200 based X shell Ford your slaping the 300 into.


Basic MINIMUM SIZE ITB references for GROSS engine dyno BHP per cylinder,

assuming a 5 inch from butterfly to valve head and a max of 9,000 rpm are;

Up to 30 BHP - 30mm, 180 hp six
up to 33 - 32mm, 198 hp six
up to 39 - 35mm, 234 hp six
up to 46 - 38mm, 276 hp six
up to 51 - 40mm, 306 hp six
up to 56 - 42mm, 336 hp six
Up to 65 - 45mm, 390hp six
up to 74 - 48mm, 444 hp six
up to 80 - 50mm, 480 hp six
up to 87 - 52mm, 522 hp six
up to 93 - 54mm, 558 hp six.

Divide by 25.4 to get proper units, and then multiply by 1.2 to get the indicative carb throttle size.


I've underlines FTF'S 58 MM intake throttle to the head suggestion. Well, It works out to a 1-7/8 venturi and a 2.28" throttle. You'll not find that easily.
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Single 4bbl verses multi carbs

Post #61 by THE FRENCHTOWN FLYER » Wed Sep 23, 2020 10:31 pm

Multi carbs look cool.
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Re: Single 4bbl verses multi carbs

Post #62 by Red rose racer » Thu Sep 24, 2020 12:02 pm

Yes they do look good, I kind of had a handle on the BB521 , I have to go through a lot of information on the I 6, but that’s what I aim to do, and thank you

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Re: Single 4bbl verses multi carbs

Post #63 by Red rose racer » Thu Sep 24, 2020 12:45 pm

Thank you X for all the information on multi carbs, I like the carbs better, but it may be time to go injection. I will not have a space problem, the I6 is going in a purpose built sand racer. I will build the truck around the I6 motor. I want to finish small twin turbo

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Re: Single 4bbl verses multi carbs

Post #64 by xctasy » Thu Sep 24, 2020 9:19 pm

In post 60, the table uses the Weber/ PMO chart which was back calculated to SAE Net. Turboing is adding boost so it allows you to reduce ( or rather, keep a stock common size) carb by the efective boost ratio. A 444 hp 300 six with three Dominator 1150 splits on 10 pound of boost only needs a three 650 cfm 2 bbl carbs with 1.4375 inch venturis.

Zeroing in if you use a group of three 500 cfm carbs with six 1.375 venturis like the Keith Dorton PN 4412, then it normally flat line at 248 hp at about 4000 rpm without Boost on 300 six. An unintercooled 10 pounds of boost, and you have an effective 1.65 boost ratio or well over 400 hp using two tiny turbos. The triple 500 Holleys with an Edelbrock external Weber jet kit allows you to make an easy 425 hp net on a log head 250 six on 12 pounds un intercooled.

Upstream is a group of two auxilary low pressure injectors, feed GNX auxilary 7 th injector style for additional enrichment.

That is what the Fazer package below was designed around...the principal that cheap Holley 2bbls with no major modifications could be added to an in line six with no major intake mods except two extra holes for the outer carbs, and the Keith Dorton style Restrictor plate cam set up for inertial ramming.

Fuel trim on the carbs is external by three bank fired pulsewidth injector signals to the power plate, and a MAF transform comes from the turbo inlet throttle body. So its an EEC V with fuel trim on the carbs and a Cobra 90 mm MAF signal to tune the whole thing.
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XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Single 4bbl verses multi carbs

Post #65 by sdiesel » Sun Sep 27, 2020 1:21 am

I am utterly lost in this but sounds cool.
...yea, just drawing blanks.
You are reference- ing, with boost you can get away with smaller venturis? Or something.....
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

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Re: Single 4bbl verses multi carbs

Post #66 by xctasy » Sun Sep 27, 2020 2:11 am

sdiesel wrote:I am utterly lost in this but sounds cool.
...yea, just drawing blanks.
You are reference- ing, with boost you can get away with smaller venturis? Or something.....


Lotus Esprit turbo and non turbo had the same carb sizes despite the turbo getting a 70 hp boost from 7 pounds ex Carb Mustang style T3 Garret Air Research boost. Any time you turbo, to whatever level, you can keep the idealized non turbo hp Port on Port ITB sizes.

For Lotus Euro spec, 1981, 160 hp with 36 mm venturis and two 45 mm carb throttles in a 2173 cc car. Add 7 to maybee 9 psi boost, same car made 230 hp turboed. Same carbs except emulsion tubes.

A generlisation from that specific is the 1979 to 1985 model year 1962cc Alfa Romeo Alfetta Turbo Delta. Same thing. Non turbo and turbo versions had the same 40 mm Dell Orto carbs. One had I dont know, 125 hp stock, the other 170 hp with turbo.

On a little 2.0 or 2.2 twin cam four with twin carbs...to get 45 to 70 hp extra without a turbo, you have to up size the carb and its venturis 8 mm or so....thats mega expensive Weber DCO 50 mm side drafts or Weber 48 mm down drafts right there with 40 to 44mm venturis.

When Ford made 240 to 260 hp BDG Cosworth Four cylinder race engines for the World Rally Championship, it found Lucas Mechanical injection was cheaper than Webers expensive DCO's or Downdraft IDAs or IDFs.

A great example from Preparation H's 300 Ford making about 400 hp net from three Weber ID 48s with six 42 mm venturi carbs.

The Holdener Hey.


Image
"Hey. I wonder how this thing would go with BOOOOSSS+!"

Answer. No carb size increase, and whatever PSI you add. No carb size increase required. Turbos dont require a carb size increase with even 9 pounds of boost. To get oven that 556 hp in post 60 above requires HUGE 54 mm venturi carbs. With a turbo, you dont need a port on port or ITB car size increase...at least at boost ratios of 1.4 or so.
Last edited by xctasy on Sun Sep 27, 2020 2:38 pm, edited 3 times in total.
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Single 4bbl verses multi carbs

Post #67 by Red rose racer » Sun Sep 27, 2020 12:18 pm

This just keeps getting better and better, I am reading the turbo book pmuller suggested , lm not sure lm understanding more, but maybe.

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Re: Single 4bbl verses multi carbs

Post #68 by pmuller9 » Sun Sep 27, 2020 1:41 pm

Red rose racer wrote:This just keeps getting better and better, I am reading the turbo book pmuller suggested , lm not sure lm understanding more, but maybe.

I recommended the book on EFI but if you need clarification on EFI or turbochargers just ask.
We have a very knowledgeable group of members.

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Re: Single 4bbl verses multi carbs

Post #69 by Red rose racer » Sun Sep 27, 2020 8:56 pm

I was just wondering, in my planning, to finally end up twin small turbos or maybe holly sniper and turbo would the early 240 rods prepped and good piston hold up to turbo boost over say 400 to 425 hp. When I do ad turbo. Do not worry I have full confidence in you and the good people on this site pmuller. I am 100% in and under your totolage

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Re: Single 4bbl verses multi carbs

Post #70 by pmuller9 » Sun Sep 27, 2020 9:24 pm

We use the 240 rod to raise the wrist pin and reduce piston size and weight for higher rpm naturally aspirated application.
This is an AutoTec piston for the 240 rod on a 300 crank with a 10 cc dish for 9.75 compression ratio.
Image

The problem is the high wrist pin doesn't leave room for a wide upper ring land for boosted application or much rod clearance under the piston dish for a deeper dish for the lower compression needed for boost.
As you can see the wrist pin is up into the oil ring groove.

The 6.385" long small journal BBC rod is preferred.
It is longer than the stock 6.21" rod but still allows plenty of room for the two above considerations.
It is also much stronger than the 240 rods by a large margin.
https://www.summitracing.com/parts/cpi-b6385ds3b4ah

When you do turbocharge you are looking at 500 to 600 ft lbs of torque and 500 hp without trying very hard.

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Re: Single 4bbl verses multi carbs

Post #71 by Red rose racer » Tue Sep 29, 2020 6:16 pm

The 500 foot pounds and 500 hp, Is what I had in mind all the time. Aldougth it will take longer, that’s we’re I want to be at the end of building. The lower end has to be done first. A tear down first, to know what parts I need, winter work on head. Would Clifford 2 -4bbl. Flow enough to support 500 lbs of touque and 500 hp. Or would I have to make a intake.


I originally thought of using 2-2bbl. Carbs on 2-4 bbl intake. Now looking more at injection. What type of injection would you use for the 500&500.

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Re: Single 4bbl verses multi carbs

Post #72 by xctasy » Wed Sep 30, 2020 7:07 am

Red rose racer wrote:The 500 foot pounds and 500 hp, Is what I had in mind all the time. Although it will take longer, that’s we’re I want to be at the end of building. The lower end has to be done first. A tear down first, to know what parts I need, winter work on head. Would Clifford 2 -4bbl. Flow enough to support 500 lbs of torque and 500 hp. Or would I have to make a intake.


I originally thought of using 2-2bbl. Carbs on 2-4 bbl intake. Now looking more at injection. What type of injection would you use for the 500&500.


Take the Dual 4bbl intake, and get two 650 double pumpers with a 1:1 linkage and drop one barrel out of each carb like Smokey Yunick or Grumpy Jenkins did on his independent runner Rat Roaster or Tunnel Ram Chevy V6.

took a SBC V8 manifold, and cut it down. 8BBL Dual Quad became an 8bbl Dual Quad with 1 bbl blocked off on each carb.

Image

Image

On top, if it wasnt EFi, were two 4bbls with one barrel blocked off with a blanking plug. Pure Keith Dorton stuff.
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
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Re: Single 4bbl verses multi carbs

Post #73 by sdiesel » Wed Sep 30, 2020 11:14 am

For the quoted figures of 500/500, may I suggest the batch fired port injection?

I'm clearly a lesser voice in this commentary, but the 500 is tilting to the extreme end of the engines capabilities.
My logic tells me that having as much control over fuel placement/distribution, and eliminating the issues of drop-out would almost require a ford EFI intake with suitable modifications to reach your goals.
Additionally I am assuming daily use reliability, over the "seldom-seen" variety of automobile that comes out on track day or nice weather days.

Personally, I would like to see the entire ford EFI system used in conjunction with a piggyback like quarterhorse. the ford system is capable of this task of 500/500 I believe. A brilliant system the EEC-IV , after unlocking timing, and there is a ton of support for it on other forums.
a long love affair with the 300 six.
my lastest and final fling is a fresh 300 in an 88 ford f350 dually 4X flatbed

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Re: Single 4bbl verses multi carbs

Post #74 by pmuller9 » Wed Sep 30, 2020 11:14 am

Red rose racer wrote:The 500 foot pounds and 500 hp, Is what I had in mind all the time. Aldougth it will take longer, that’s we’re I want to be at the end of building. The lower end has to be done first. A tear down first, to know what parts I need, winter work on head. Would Clifford 2 -4bbl. Flow enough to support 500 lbs of touque and 500 hp. Or would I have to make a intake.
I originally thought of using 2-2bbl. Carbs on 2-4 bbl intake. Now looking more at injection. What type of injection would you use for the 500&500.

I would not use the Clifford 2 -4bbl intake for turbocharging.
You are drag racing and need good flow above 4000 rpm.
A custom large runner intake will maximize your performance using minimum boost.
I would use the Holley HP universal system for a port injection EFI.

Would it be beneficial to run a distributorless ignition because of water or mud?

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Re: Single 4bbl verses multi carbs

Post #75 by Red rose racer » Thu Oct 01, 2020 10:09 am

Sdiesel this will be a purpose bilt sand racer, not everyday driver.

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Re: Single 4bbl verses multi carbs

Post #76 by xctasy » Thu Oct 01, 2020 6:09 pm

This is a 6 barrel math class. I found this out from David Vizard saying a 4bbl on a 4 cylinder Pinto engine will idle better than a 2-bbl, but that idle was always touchy with Holley's and too much cam duration. That got me thinking....


I really like Cliffords Dual Quad intake, but I like ITB/ Port on Port, Isolated Runner stuff more because you can reduce carb size with a turbo instillation, and still get the huge 15% power benefit of pulse tuning. Or carry the same power with 600 rpm less. Every RPM is scared.


This is what World Champ Gramps Preparation H Maverick was based on, and why all the great Fords before restrictor plates have tended towards Independent Runner systems.

If Total Performance didn't die a death in the USA, and it actually carried on like it did in Australia another 2 years till 1973, the Big Sixes would have been running cut down Dominator 1150 1.8125 venturi splits and making 500 hp gross from 5 liters, I am quite sure.


the 1050, 1-11/16 is a 1.6875" venturi.
and 1150's have the larger 1-13/16 or 1.8125" venturi


I see life with Leaded Hi Octane Tinted Sun Glasses because of the information from people who have been saw cutting expensive Holley 4500 carbs 's since 1969 on 429 Shot Gun engines.

I guess none has twigged to something I learned in Pat Ganhals V6 Performance book. How to make an Independent Runner ITB V-6.

V 6 Performance Paperback – June 1, 1982
V6 Performance Pat Ganahl
Buick Ford & Chevy

SA Designs 1982 ISBN 09314213X

by Pat Ganahl (Author)


Image

I respect American SA and HP books to much to rip images, although I have done it with David Vizard because people don't seam to get it when he simply explains something, SIMPLY, and people simply don't get it...

Sometimes a picture doesn't even help when promoting an idea, so the right thing to do is throw the ball again and again until you get a feedback that suggests others get it.

Here is my take an outworking of Grumpy's ITB/ Port on Port, Independent runner Cut down V8 Tunnel Ram ---> GM V6 racing engine idea from that 1982 book.



Image


Picture source
viewtopic.php?t=48448

super4ord wrote:Here's a decent shot of the Clifford's I've found. The triple Holley style with the adapters and the triple downraft Weber style are NOS. The mag is a Ronco. Haven't decided on which intake to use yet. I kept one forged crank too. Sold the other to Gord. I'm still looking for an SVO block and waiting on Mike's 300 head. Image[/img]



Now some details. When each port to an intake valve is ITB/ Port on Port, Independent runner, the Carb venturi's then only need a bare minimum of carb venturi to trigger a certain horsepower. Note...carb venturi size, not throttle size.


So it works by this matrix of numbers. I don't like mm's,
hp gross at per cylinder and total
Up to 30 BHP - 1.181" 30mm, 180 hp six
up to 33 - 1.250" 32mm, 198 hp six
up to 39 - 1.375" 35mm, 234 hp six
up to 46 - 1.500" 38mm, 276 hp six
up to 51 - 1.575" 40mm, 306 hp six
up to 56 - 1.650" 42mm, 336 hp six
Up to 65 - 1.750" 45mm, 390hp six
up to 74 - 1.888" 48mm, 444 hp six
up to 80 - 1.969" 50mm, 480 hp six
up to 87 - 2.047" 52mm, 522 hp six
up to 93 - 2.125" 54mm, 558 hp six.

650 4 BBL 4150 Series Holley Carbs have
Venturi inlet: 1-1/4"
Throttle bore: 1-11/16"

that's 31.75 mm, enough for 198 hp. On a 300, a BT, Before Turbo, before an blow through turbo hat on conversion, the power band would be at 3600 rpm. You would have to 22 pound boost, and that might give a 2.52 boost ratio, and maybee, 500 hp gross.


For a Twin Converted 3 bbl, the 255 to 310 hp range is here. To get 500 hp boosted, you come down on effective boost ratio. 14 pound for the BG Demon RS 1.425, 9 pounds for the Holley Ultra 1.600.

4150 carbs with 1.75" throttle plates.

1. BG Demon RS 1.425 venturi

2. BG Gold Claw 1.500 venturi

3. QFT/Proform 1.450 venturi

4. QFT/Proform 1.520 venturi

5. QFT/Proform 1.590 venturi

6. Holley Ultra 1.580 venturi

7. Holley Ultra 1.600 venturi


AED, CSU, any number of brilliant ITB tuners can sell you custom adjusted venturi's.

The 4150 4bbl based Braswell B-4825 Series carburetor is offered with venturi sizes from 1.40" up through 1.68", and throttle bores of 1.688", 1.750", or 1.790
The biggest carbs are 4500 based Dominators and CSU's.

Braswell and many others make different venturis. 1.90"-2.22" venturis and 2.20"-2.60" throttle bores on the B-7520 2-bbls and B-7395 4-bbls.


I like Dual 660 center squirters,
triple 500 Holleys with the venturis taken out from 1.375 to 1.4375 by fettling, and those give you an Isolated runner 255 - 265 HP with relative ease, at about 4600 rpm. Then add 14 pound boost, and you've got an assurance of 500 hp.

Any time you increase the venturi's to serving more than one cylinder, the pulse tuning effect dies, and your better off forgetting all this ITB/IR/POP hocus pocus.

That's the 6bbl math.


So the summary is for six barrels, 198 to 310 hp from 1.25 to 1.600 venturi carbs. To get 500, as much as 22 pound of boost or as little as 9 pounds.


Now, if you use three 4-bbl carbs, the average Venturi areas must match the table I used above. it becomes 12 bbl math.

So donner Dual 2bbls and 4bbl Hitachi/Nikki Holley's are here :-


Image

You would need "six" 2bbl Escort carbs to make an independent runner 300 produce just 198 hp at 3800 rpm.
You would need three RX-7 carbs to make an 300 produce 234 hp at 4200 rpm
You would need three 390 cfm 4bbls to make 276 hp at 4700 rpm
You would need three 450 to 465 cfm 4bbls to make 306 hp at 5100 rpm
You would need three Custom venturi 480 -500 cfm 4bbls to make 336 hp at 5400 rpm
You would need three 550 cfm 4bbls to make 390 hp at 6000 rpm, or a triad of 660-4160, 650-4011,600-4010, or 600-4150/4160/4180
You would need three 700 cfm 4bbls to make 444 hp at 6500 rpm
You would need three 725 cfm 4bbls to make 480 hp at 6700 rpm; Q-jets or ThemroQuads would work
You would need three 800 cfm 4bbls to make 522 hp at 7100 rpm
You would need three 830-1050 cfm 4bbls to make 558 hp at 7500 rpm
You would need three 1150 cfm 4bbls to make 612 hp at 7800 rpm


This backs up post viewtopic.php?f=2&t=77272&p=594767&hilit=Mazda+4bbl#p594767
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Single 4bbl verses multi carbs

Post #77 by Red rose racer » Sat Oct 03, 2020 1:23 am

Are you saying that this could be a good allturntive to port injection. It probably won’t be any cheaper, and harder to tune. This is very good lnformation though.

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Re: Single 4bbl verses multi carbs

Post #78 by xctasy » Sat Oct 03, 2020 5:43 am

Yes. Sequential Fuel injection attempts to copy Weber ITB pulse tuning. Carbs can make more power than EFi.

But ITBs have a very narrow band of venturi size and carb size to work with. Even a 60 thou differnce small or large, can hurt power and mid range torque. So you have to have a very clear idea of before boost power curve targets, then add your boost factor.

I do love MegaSquirt, and suggest you copy Mike 1157's gange fired EFi cross flow six ITB system usings six M3 BMW S52 injectors. Advance Search Mike1157 and enter xctasy.
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Single 4bbl verses multi carbs

Post #79 by pmuller9 » Sun Oct 04, 2020 9:42 pm

How are you doing on EFI and turbo reading material?

Are you still going to go naturally aspirated at first or go right to a turbo engine?

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Re: Single 4bbl verses multi carbs

Post #80 by Red rose racer » Sun Oct 04, 2020 11:32 pm

The more I read the more I get indecisive. The ITB port pulse tuning is very interesting. I get this way when I am gathering lnformation. Then I say this is what I will do,and go full bore.. like the lower end, it’ll be the BB Chevy 6.385 rods ( Compstar) I believe and piston to be determined by block conditions.

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Re: Single 4bbl verses multi carbs

Post #81 by pmuller9 » Wed Oct 07, 2020 10:52 pm

In this video are two intake manifolds.
The second one with the round plenum attached to individual runners and a throttle body at the end (nicknamed the "Cannon") is the style that would work for both naturally aspirated and turbocharged drag racing application.
This is what I was trying to refer to at the beginning of this thread.

https://www.youtube.com/watch?v=YWcZMjA7ZgQ

You can consider it as an independent runner intake with all benefits described in the above posts only with a single throttle body entry point.

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Re: Single 4bbl verses multi carbs

Post #82 by xctasy » Wed Oct 07, 2020 11:11 pm

pmuller9 wrote:In this video are two intake manifolds.
The second one with the round plenum attached to individual runners and a throttle body at the end (nicknamed the "Cannon") is the style that would work for both naturally aspirated and turbocharged drag racing application.
This is what I was trying to refer to at the beginning of this thread.

https://www.youtube.com/watch?v=YWcZMjA7ZgQ

You can consider it as an independent runner intake with all benefits described in the above posts only with a single throttle body entry point.


Up front Single Throttle body, Cannon Air Atrium

Image

Hogan style manifold with down draft throttle body

Image

Sequential Injection Cam Synchronizer with Bernstein sensor
(for Port EFi sequencing which is no longer every second injector gang fired)

Image
Image
XEC Ltd ICBE's Inter Continental Ballistic Engines-
FAZER 6Bi (M112 & EEC5) or FAZER 6Ti (GT3582 & EEC5) 425 HP 4.1L/250 I-6
FAZER 6V0 3x2-BBL Holley 188 HP 3.3L/200 I-6 or 235 HP 4.1L/250 I-6
X-Flow Engine Components Ltd http://www.xecltd.info/?rd=10

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Re: Single 4bbl verses multi carbs

Post #83 by Red rose racer » Thu Oct 08, 2020 1:21 pm

The video s were very good.you would have to be very knowledgeable about the Hp systems to make lt work. That’s not for a novice,I believe. I like them both,exspecicially the cannon. I would need a lot of directional help to make them work. Mostly the wiring part. I have some ideas on building the cannon, like how to put the slite taper in equal length runners that FTF spoke about in a previous post. I just don’t know what size each end is dimensionally

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Re: Single 4bbl verses multi carbs

Post #84 by pmuller9 » Sun Oct 11, 2020 10:41 pm

Red rose racer wrote:The video s were very good.you would have to be very knowledgeable about the Hp systems to make lt work. That’s not for a novice,I believe. I like them both,exspecicially the cannon. I would need a lot of directional help to make them work. Mostly the wiring part. I have some ideas on building the cannon, like how to put the slite taper in equal length runners that FTF spoke about in a previous post. I just don’t know what size each end is dimensionally

The wiring is easier than you think and the instructions are good.
Don't look at the whole job at once. Focus on the individual parts of the system.
You just wire each sensor, injector, ignition component and any other device you need to control one at a time until you are done.
We are also here to help.

One thing about a large racing cam, there is no ignition timing advance curve. You set the timing at what would have been full advance say 34* BTDC
If you are turbocharging you can set the timing a little retarded and pull timing from there as boost increases.
You can retard the timing at cranking rpm to help the starter.

The intake manifold runners start as the same size as the intake ports on the head and taper out from there.
The head should be completed first to get the dimensions.

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Re: Single 4bbl verses multi carbs

Post #85 by Red rose racer » Tue Oct 20, 2020 10:41 am

Thank you thank you, thank you this site was not available to me for nearly 2weeks I thought I lost all the good lnformation that was given to me.

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Re: Single 4bbl verses multi carbs

Post #86 by pmuller9 » Tue Oct 20, 2020 12:26 pm

We all had the same concerns.
I'm going to take the time to copy a lot of info to my own system for safe keeping and highly recommend everyone else do the same.

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