Making a Low rpm Triple 350 cfm carb setup

Ahhh--waitaminute, there is a but here.

What if you have an engine that doesn't have a removable intake so that you can use that big carb?

Exactly. Those two or three two-barrels line up right nicely on the log intake. It's impossible to put a four-barrel on there, and the biggest two-barrels only flow 350-375 CFM when measured like a four barrel carb.* The solution is more than one carb. A properly set up triple will dump no more unburned gas out of the tailpipe than one big carb. Also, with triples the option is there for progressive linkages, which reaps even more fuel mileage benefits while keeping the top end intact.

Plus they look really, really cool. 8)

*The flow rates are measured at different pressures. To get the equivalent four-barrel size, divide the two barrel rating by 1.414.
 
Hmmm. 3 progressive vacuum operated 2bbls would be perfect. Does anyone know of a good 2 bbl progressive vacuum operated carb? The ideal carb would have availability for jets and such like a HW.
 
H/W = Holley Weber Holley made a version of the Weber DFV/DGV that most of the big 3 used on thoer 4 cylinder cars.
 
Yah, was saying that the H/W would probably be the ideal.

Didn't Rochester make a 2V that had vac secondaries? Like half of a Q-jet? Might be worth looking into.
 
Ah. Well, the H/W is the only vac secondary progressive 2V I've heard of. Seems like the logical choice for triples in a non-IR setup.
 
There is, or was a Holley 2305 two barrel. 350 cfm progressive secondary. They quit making them. :cry: I know where one is, and I can't wait to se how it runs. 8)
 
Actually the HW is a mechinical secondary. I think most Japanese carbs are vaccum secondary but, I have no idea if any of them have jets and such available for them. With so many carbs, you would want small ones. it would be really cool to make the open progressively. It would be like 3 dueces on a v8 runing primarily on the center one. Then when you put your foot in it the others would start working. As the RPM rose the vacuum secondaries would open to mauch the flow needed. It would probably be a pin to tune though.
 
The manifold you show isn't IR - you have a miniature "plenum" below each carburetor where the mix from both barrels merges, then separates to feed the cylinder separately. This will clean up jetting a bit and works well (since Jaguar used it with the 3 X 2" SU) but does not have the reversion-immune and tuned length characteristics of a completely separated IR.
Running a single carb simply will not work regardless of how the linkage is activated. Each cylinder must pull equal vacuum on whatever carb(s) are used, or those cylinders become a parasitic load. Progressive must have a shared plenum with all cylinders all the time - the volume, shape etc. can vary somewhat but if it's too irregular you'll have distribution problems that cannot be jetted out.
 
They don't have to have a shared plenum. They can have a ballance tube like most of the SU setups. Large enough to level out pulsing.
 
Why can I see the opposite port opening in the right-hand base? There is no divider between the barrels.


34248941.jpg
 
xctasy":27ep7t3i said:
A 200 Falcon six with three #7448 or 9117 350 cfm carbs needs a cam which provides power at below 5000 rpm, possibly 4800 rpm.
Click to expand...

Aren't you sacrificing potential HP for manifold velocity to operate 3/ 350 cfm carbs on a 200CID engine? Granted the fuel distribution would be better, but adjusting your cam timing to suit an over-carbed engine is a little backwards to me. Don't you select your induction (CFM) after your head flow and cam are sorted out?
 
Aerowrench":36l0y0yi said:
xctasy":36l0y0yi said:
A 200 Falcon six with three #7448 or 9117 350 cfm carbs needs a cam which provides power at below 5000 rpm, possibly 4800 rpm.
Click to expand...

Aren't you sacrificing potential HP for manifold velocity to operate 3/ 350 cfm carbs on a 200CID engine? Granted the fuel distribution would be better, but adjusting your cam timing to suit an over-carbed engine is a little backwards to me. Don't you select your induction (CFM) after your head flow and cam are sorted out?
Click to expand...


I am reverse engineering. Maximum power is nothing on a car that needs a full, deap torque curve to opperate. Knowing what I know about the 250 is that it isn't ment to rev, and gives its best at the low to middling rev range. Even the latest 2007 255 hp DOHC Falcons use the low end torque to get them around.

I have a 250 X-flow EFI with 268 degree cam and 1.125" ports. I pretty sure that will make a set of triple 350cfm carbs run out at about 3500 rpm. The cam normally runs out at 4000 rpm.

Since most US Falcon sixes have a lousy iron log head and a 252 or 256 cam, I'm pretty sure that a triad of 350 cfms carbs can be calibrated, and work like an EFI system on the street.

I'm convinced that even at 3500 rpm, a port on port multi carb system will yield better power than the 164hp and 247 lb-ft I get with the EFI at the moment, and, dollar for dollar, that beets a cam and head change if you can just bolt on three carbs and maybee a good exhast system.
 
I want to know what is the most HP one can or has made with a 200 CI utilising the original head and not cheating with an aussie head.
With regards to keeping the log intact and not sawing it off.... :)


Anyone have any ideas?


FE
 
FALCONAROUND":drcadr49 said:
I want to know what is the most HP one can or has made with a 200 CI utilising the original head and not cheating with an aussie head.
With regards to keeping the log intact and not sawing it off.... :)


Anyone have any ideas?


FE
Click to expand...

Triple 500 cfm Holleys on a 200 block with D8 head will give up to 215 hp at 5500 rpm if the cam and carbs are jetted to suit. When you have port on port induction, and the right size the power gains are simply huge. To package the linkage and bowls up, and create a good port matching would be a trick.

I'm quite a way down that path now with my X-flow.
 
Based on a locked off, totally blocked Power Valve on a 2300 series 350 cfm carb with stock Holley venturi.

For cross checking the sizing an IR set-up for a low rpm triple 350 cfm carb set-up, I've used the following Weber call size jets from another website application. Each graph is a generic one for 1.6, 1.9, 2.1, 2.2 and 2.4 liter DOHC Alfa Romeo engines.

Twin DCOE 40 Weber with 28 mm chokes for a 1.6 liter DOHC Alfa Romeo engine= 144 cid Ford Falcon six reving to 5000rpm. 115 micron Weber =152 cc/min=115 microns is a 45.28 thou jet, or close to a 149 cc/min or 44 thou nominal, 44 call size Holley 2300 jet




Twin DCOE 40 Weber with 31 mm chokes for a 1.9 liter DOHC Alfa Romeo engine= 170 cid Ford Falcon six reving to 5000rpm. 125 mircron Weber = 201 cc/min=125 micron is a 49.21 thou jet, or close to a 198 cc/min or 50 thou nominal, 51 call size Holley 2300 jet. Very close is the 205 cc/min or 52 thou nominal, 52 call Holley 2300 jet. Note that Holley also makes some Close Limit jets in the 51 to 52 jet size.



Twin DCOE 40 Weber with 31 mm chokes for a 2.1 liter DOHC Alfa Romeo engine= 188 cid Ford Falcon six reving to 5000rpm. 125 mircron Weber = 201 cc/min=125 micron is a 49.21 thou jet or close to a 198 cc/min or 50 thou nominal, 51 call size Holley 2300 jet
Very close is the 205 cc/min or 52 thou nominal, 52 call Holley 2300 jet. Note that Holley also makes some Close Limit jets in the 51 to 52 jet size.





Twin DCOE 40 Weber with 33 mm chokes for a 2.2 liter DOHC Alfa Romeo engine= 200 cid Ford Falcon six reving to 5000rpm. 135 micron Weber = 251 cc/min=135 microns is 53.15 thou jet or close to a 248 cc/min or 56 thou nominal, 57 call size Holley 2300 jet
.


Twin DCOE 40 Weber with 34 mm chokes for a 2.4 liter DOHC Alfa Romeo engine= 221 cid Ford Falcon six reving to 5000rpm. 140 micron Weber = 275 cc/min=140 microns is 55.12 thou jet, or close to a 267 cc/min or 58 thou nominal, 59 call size Holley 2300 jet jet



Chart 1:
jetsize.gif


Chart 2:
The jet sizes for Holley Webers are:-

103 cc/min=105 microns, or 41.34 thou
128 cc/min=110 microns, or 43.31 thou
152 cc/min=115 microns, or 45.28 thou
178 cc/min=120 microns, or 47.24 thou
201 cc/min=125 microns, or 49.21 thou
225 cc/min=130 microns, or 51.18 thou
251 cc/min=135 microns, or 53.15 thou
275 cc/min=140 microns, or 55.12 thou
298 cc/min=145 microns, or 57.09 thou
325 cc/min=150 microns, or 59.06 thou
346 cc/min=155 microns, or 61.02 thou
375 cc/min=160 microns, or 62.99 thou
400 cc/min=165 microns, or 64.96 thou
425 cc/min=170 microns, or 66.93 thou
450 cc/min=175 microns, or 68.90 thou
475 cc/min=180 microns, or 70.87 thou
525 cc/min=185 microns, or 72.83 thou

Chart 3:
The jet sizes for Holley 2300/4150/4160/4165/4175/4500 carbs are:-


Red indicates the best estimate figures. HolleyWeber and Holley 2300/4150/4160/4165/41754180/4500 jets are not the same, and I've not seen all the data for all jets 40 to 59. Smaller jets have more headloss, and flow much worse than there area would suggest. Those from 60 to 100 are form the Barry Grant © 1997, catalogue
123 cc/min or 40 thou nominal, 40 call size jet
129 cc/min or 41 thou nominal, 41 call size jet
136 cc/min or 42 thou nominal, 42 call size jet
142 cc/min or 43 thou nominal, 43 call size jet
149 cc/min or 44 thou nominal, 44 call size jet
157 cc/min or 45 thou nominal, 45 call size jet
164 cc/min or 45 thou nominal, 46 call size jet
171 cc/min or 47 thou nominal, 47 call size jet
178 cc/min or 48 thou nominal, 48 call size jet
185 cc/min or 48 thou nominal, 49 call size jet
192 cc/min or 49 thou nominal, 50 call size jet
198 cc/min or 50 thou nominal, 51 call size jet
205 cc/min or 52 thou nominal, 52 call size jet
212 cc/min or 52 thou nominal, 53 call size jet
221 cc/min or 53 thou nominal, 54 call size jet
230 cc/min or 54 thou nominal, 55 call size jet
239 cc/min or 55 thou nominal, 56 call size jet
248 cc/min or 56 thou nominal, 57 call size jet
257 cc/min or 57 thou nominal, 58 call size jet
267 cc/min or 58 thou nominal, 59 call size jet
285 cc/min or 60 thou nominal, 60 call size jet
298 cc/min or 60 thou nominal, 61 call size jet
311 cc/min or 61 thou nominal, 62 call size jet
325 cc/min or 62 thou nominal, 63 call size jet
341 cc/min or 64 thou nominal, 64 call size jet
357 cc/min or 65 thou nominal, 65 call size jet
374 cc/min or 66 thou nominal, 66 call size jet
392 cc/min or 68 thou nominal, 67 call size jet
411 cc/min or 69 thou nominal, 68 call size jet
429 cc/min or 70 thou nominal, 69 call size jet
448 cc/min or 73 thou nominal, 70 call size jet
470 cc/min or 76 thou nominal, 71 call size jet
492 cc/min or 79 thou nominal, 72 call size jet
517 cc/min or 79 thou nominal, 73 call size jet
542 cc/min or 81 thou nominal, 74 call size jet
566 cc/min or 82 thou nominal, 75 call size jet
587 cc/min or 84 thou nominal, 76 call size jet
615 cc/min or 86 thou nominal, 77 call size jet
645 cc/min or 89 thou nominal, 78 call size jet
677 cc/min or 91 thou nominal, 79 call size jet
703 cc/min or 93 thou nominal, 80 call size jet
731 cc/min or 93 thou nominal, 81 call size jet
765 cc/min or 93 thou nominal, 82 call size jet
795 cc/min or 94 thou nominal, 83 call size jet
824 cc/min or 99 thou nominal, 84 call size jet
858 cc/min or 100 thou nominal, 85 call size jet
890 cc/min or 101 thou nominal, 86 call size jet
923 cc/min or 103 thou nominal, 87 call size jet
952 cc/min or 104 thou nominal, 88 call size jet
987 cc/min or 104 thou nominal, 89 call size jet
1014 cc/min or 104 thou nominal, 90 call size jet
1080 cc/min or 105 thou nominal, 91 call size jet
1150 cc/min or 105 thou nominal, 92 call size jet
1200 cc/min or 105 thou nominal, 93 call size jet
1260 cc/min or 108 thou nominal, 94 call size jet
1320 cc/min or 118 thou nominal, 95 call size jet
1375 cc/min or 118 thou nominal, 96 call size jet
1440 cc/min or 125 thou nominal, 97 call size jet
1500 cc/min or 125 thou nominal, 98 call size jet
1570 cc/min or 125 thou nominal, 99 call size jet
1640 cc/min or 128 thou nominal, 100 call size jet
 
The Holley 2300 series carb comes with about six different venturi sizes.

Sequence No|Call Name| CFM at 3"Hg|Venturi diameters| Throttle sizes
1, Early AMC 60-64 AMC 250/327 v8,2040/2228/2442/2463 (2300c), About 275 cfm 1.125", 1.4375"
and similar 64-70 IHI V266,V304/V345, 2520/2977/4574/6380/6386, 275 cfm 1.125" venturi, 1.4375" throttle,
2, Later 65-67 287/290/327/343 v8 2699,2968, 3304-3308, 3217,3234,3262, 3483,3484,3858,3905 (2209 series) No venturi info, no rated cfm,
3, Universal Fit 7448 or 9117, or specific Mopar 6 pack 350 cfm= 1.1875", 1.5" throttle
4, 7508 425 cfm (factory Ford 424 cfm 2100 1.23 replacement carb) = 1.23", 1.5" throttle
5, 4412 500 cfm=1.375", 1.6875" throttle
6, 6245 650 cfm=1.4375 (62.5 thou overe bore on stock 500 cfm's 1.375 venturi)", 62.5 thou over 1.75" throttle, no air horn. See http://img.photobucket.com/albums/v223/ ... series.jpg

*All production Holley 2300's are technically non emmissions carbs, but there is evidence of emmissions spec components such as 2300E, 2300EG, 2380EG carb revisions using US 51 states Federal spec 4180 series Fords 1983-1989 HO 4V 5.0/5.8/7.8 float bowls


In terms of IR design, carb venturi and throttle sizes in mms are

Candidate 2300 series carbs for IR runner tuning
Type 1 275 cfm Holley 2-bbl 28.575 mm, 36.513 mm, Like a Weber DCOE 38 or DGAS 38 with 29 mm venturi
Type 2 Unknown, but most likely like a Weber DCOE 38 or DGAS 38
Type 3 350 cfm Holley 2-bbl, 30.163 mm, 38.1 mm, Like a Weber DCOE 38 or DGAS 38 with 30 mm venturi
Type 4 425 cfm Holley 2-bbl, 31.242 mm, 38.1 mm, Like a Weber DCOE 38 or DGAS 38 with 31 mm venturi
Type 5 500cfm Holley 2-bbl, 34.375 mm, 42.863 mm, Like a Weber DCOE 42 with 34 mm venturi
Type 6 650cfm Holley 2-bbl, 36.513 mm, 44.45 mm, Like an IDA 44 with 37 mm venturi

Using the Weber IR chart, each type of stock Holley 2300 carb with the power valve blocked and jetted to suithas a normal rpm limit for a given cubic inch Ford six


This validates

xctasy":1mdpstgk said:
Summary of my purpose.

1. I'm trying to bring Port on port, isolated runner 'pulse tuning' right down to our stock 252 , 256 and 264 cams used in 200 and 250 I6 Fords, and fill out the torque power and economy curves as much as possible with stock Holley 2300 series 350 or 500 cfm parts.

2. I'm defining ideal Holley carb sizes by use on existing 200 and 250 engines, and defining new so-called Y3.5, Y4 and Y4.5 values for 3500, 4000 and 4500 rpm based on the time honoured Weber Isolated runner venturi chart

Background absolutes.

1. The ideal engine capacity for 2300 series 350 and 500 cfm, or split 4500 1050 or 1150 Holleys on I6 engines is a natural log (Ln) function. The Ln function varies due to rpm at maximum power.

As listed above, the venturi sizes in mm's are listed

at Y6 (6 000 rpm) is 13.9 Ln(x)-48.9,
at Y8 (8 000 rpm) is 17.1 Ln(x)-59.6
and Y10 (10 000 rpm) is 17.9 Ln(x)-58.9

From http://forums.hybridz.org/showthread.php?p=680623, I followed a link, and found the formulae for 5000 rpm via use of a Weber Jetting program used for 1200 to 2400 cc 4-cyl engines. It confirms the Y6 and Y8 equations. For Y5, the formula is

Y5, (5000 rpm) is 12.5 Ln(x)-46.8

The carb tuning looks to be so sensitive that a venturi even a mm or 40 thou too big or too small can vary the power rpm by 200 rpm.

I'm aiming for a Y4 (4000 rpm) or even Y3.5 (3500rpm) target.

I am now summarizing that a 250 Falcon with a three #4412 500 carbs needs a cam which provides peak power at 5000 rpm.

A 200 Falcon six with three #7448 or 9117 350 cfm carbs needs a cam whch provides power at below 5000 rpm, possibly 4800 rpm.

A 250 Falcon six with three #7448 or 9117 350 cfm carbs should only need a cam which provides power to 3500 rpm to run in an optimized manner.

2. Since I have an engine block that can be built as a 200, 221, or 250, and a block which can take any Ford head, and any number of cams, I can test any engine configuration.

3. The time hounoured standard jetting of isolated runner engines with no power valve, is always 1/25 th of the venturi diameter. So a 350 will like a 48 jet, a 500 will like a 56 jet. Since one carb is working for only a third of an engine , a power valve may need to be two stage and the PVCR's have to be reduced from 53 or 62 thou down to perhaps 16 to 19 thou. Any of the commonly available two stage power valves will cover for the difference from open loop (11.5:1 , wide open throttle ) to close loop (14.7:1, cruise) conditions. This will allow an effective enrichment of 2 or 3 jet sizes whenever vaccum drops, but will do so in stages. With some science applied, a triple carb engine should lean cruise like an EFI champion.
Click to expand...
 
I am now fitting three Type 3 or Type 4 carbs to my Mustang 3.3, and a cam to suit power at 4800- to 5000 rpm. I'll adjust venturi mm's to about 30 to 32 mm or so using Addo's special venturi routing tool.

Based on getting the right camshaft, the right head flow, with the best induction flow and the best exhast flow, there should be an aspirations ratio of 4400. This exceeds the efficiency of a single 2-bbl carb 200 cubic inch engine made for performance. From evidence I've posted before, the figure 4800 is about the best one copuld expect with a 2-bbl carb six, as there is no pulse tuning in a 2-bbl six cylinder engine. There is signifcant pulse 'super-charging' when an IR system is employed, more than 10%, and when the flow efficency viaration from cylinder 1 and 6 verses 3 and 4 is concerned, a similar boost should be able to be optimised by good cam selection.

Hence peak power is 200 cid * 5000 rpm/4400= 227 hp.

Comparing the Weber DCOE series to the known cfm of the 275, 350, 500 and 650 cfm carbs is done using this chart. Source of CFM's is David Vizards Modifying your Aseries Engine, and some other Modifiying Fords SOHC engine. They were measured in a Supeflow flow bench at 1.5" hg, and have conversion to the 3.0"Hg rating Holley 2-bbls use via a 1.41 multiplier used for pressure head conversions

Here are flow figures for Triple DCOE carbs with the best trumpets fitted to the ends.

40 DCOE , 24 mm, 202 cfm at 1.5" Hg = 286 cfm at 3.0" Hg
40 DCOE , 26 mm, 241 cfm at 1.5" Hg = 341 cfm at 3.0" Hg
40 DCOE , 28 mm (Fiat 2300S), 279 cfm at 1.5" Hg = 395 cfm at 3.0" Hg
40 DCOE , 30 mm, 316 cfm at 1.5" Hg = 447 cfm at 3.0" Hg
40 DCOE , 32 mm, 336 cfm at 1.5" Hg = 475 cfm at 3.0" Hg
40 DCOE , 34 mm, 346 cfm at 1.5" Hg = 489 cfm at 3.0" Hg
40 DCOE , 36 mm, 350 cfm at 1.5" Hg = 495 cfm at 3.0" Hg
45 DCOE , 32 mm, 324 cfm at 1.5" Hg = 458 cfm at 3.0" Hg
45 DCOE , 34 mm, 376 cfm at 1.5" Hg = 532 cfm at 3.0" Hg
45 DCOE , 35 mm, (Torino GR) 397 cfm at 1.5" Hg = 562 cfm at 3.0" Hg
45 DCOE , 36 mm, 418 cfm at 1.5" Hg = 591 cfm at 3.0" Hg
45 DCOE , 38 mm (E37 Pacer), 438 cfm at 1.5" Hg = 619 cfm at 3.0" Hg
45 DCOE , 40 mm (E49 Charger/Tornado 380 Motor w TC), 444 cfm at 1.5" Hg = 628 cfm at 3.0" Hg

Venturi Size for venturi size, our 2300 carbs flow a lot less when there is a stock choke on the air horn.

If a Weber DCOE 38 or 40 had a 29 mm venturi , it would a flow of 421 cfm . A similar size early AMC/IHI/Ford 275 cfm Holley 2040 flows 53% less due to a choke air horn.

A Weber with a 30 mm venturi flows 447 cfm. It would outflow a same size venturi 350 cfm Holley 7448 by 27%.

If there was a Weber with a 31 mm venturi, it would flow 461 cfm, or 8% more than a 425 cfm Holley 7508

A Weber with a 34 mm venturi flows anywhere from 489 to 532 cfm, so it flows the same as a similar size 500cfm Holley 4412. Either 2% less or 6% more. An example is the Renault Torino 3.8 L6 with 215 hp triple Weber 45 DCOE with 35 mm chokes is similar to three stock 500 cfm 4412 Holleys with its stock 34.5 mm chokes. Peak power rpm is incidently about 4700 rpm with this carb on the 3.8 liter Kaiser based six see viewtopic.php?f=13&t=29958,

With 40 mm chokes and a better cam, theTornado 380 w TC did 248 hp at 5000 rpm. See http://www.torosite.com.ar/torinoytornado.html

If a Weber had a 37 mm venturi, it would flow 598 cfm, and that is 9% less than a similar size 650 cfm Holley 6245. An example close is the E37 265 Charger/Pacer, which gave 248 hp at about 4800rpm from 4.3 liters

Summary is that small 275 and 350 cfm Holley’s flow a lot worse than a similar sized DCOE Weber’s, due to the restrictive choke air horn.L arger 500 and 650 cfm Holley’s flow just as well as large Weber’s.This implies that venturi enlargement is advantageous on 275 to 350 cfm Holleys.There is enough space for a 150 thou rout out of a stock small 2040 or 7448, and that would bring cfm up significantly. I'm looking a 1.277" for my 7508 and 9117 list Holleys which would make an extra 11% on a Weber, but more likely to be up to 27% on a Holley 275/350. Note that the smaller carbs often come with truck or economaster boosters, which loose 15 to 30cfm on the 500 cfm boosters. Annular discharge boosters from the Holley 2380EG and 4180G Ford truck and bus carbs bring back the loss, adding 15 to 30 cfm. Additionally, there is a new batch of US Coast Gaurd approved return line 2300 carbs for OMC under new Holley part numbers which allow later bits to be fitted to earlier Holley carbs. Adjustability with the Holley 2300 2-bbl is now total.

This sumarises the background premise of project ITZOLD 200 6v over 200 hp engine viewtopic.php?f=5&t=65023
 
Deano, you know i've been cogitating on this (for a different engine) since you advised me on it. Let me ask about something which someone has surely thought of and tried, though I've not heard of it anywhere, for the reversion problem you mentioned up the thread a ways. You know about the anti-reversion exhaust headers that have a wave-dampener in the entry from the port; could this same trick be used to advantage in your I.R. intake, immediately below the carburator base?

And if that won't do, what about the "Roost-Boost" (I think it was called), a kind of surge-damper or wave damper used by some owners of 2-stroke dirt bikes years ago? Could you have a single chamber with hoses or tubes to each intake tract?

Finally, the engine I have is mounted east-west, but your six runs north-south (as nature intended engines to do). Therefore, my floatbowls will aim toward the front of the car, but yours will point to the side. Won't that mess with the metering on accelleration/decelleration?
 
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