Holley 2 and 4-bbl Jetting for any engine.

Ok, this is a long one. The xecute-ive summary first:

Jets for #5200 Holley/Weber and Weber 32/36 carbs:

5.5 times the estimated net hp at the flywheel gives the Total cc per minute required. Add primary and secondary jets together to get the result.

Eg.1 32/36 with 65 Idle, 150 primary, 135 secondary. From the chart RougeS posted, at http://members.cox.net/gork1/jetsize.gif

Please note that these are stamped in either Microns ( not mm , but mm/100), a silly metric measurement, or cc/min, a silly metric measurement. But hey, silly metrics are okay as long as the help me jet my in-line six right!

Say you hope to have 125 hp at the flywheel of your new 200 rebuild, and you need to jet it to suit. Well, just take that 125, and times it by 5.5, and this gives 687.5 cc/min jetting required. Since the existing jets are 150 and 135, then the flows are 325 plus about 251 cc/min, or 576 total. I'd say that was to small, because 576 divided by 5.5 is about 105 hp. So pump up the jet size on primary and secondary to 155 and 140. That's, from RougeS's chart, about 621 cc/min from the 346 and 275 cc/min readings these jet give. 621 divided by 5.5 is about 113 hp.
Still to small for 125hp. Go to 160 and 145, at 375 and 298 cc/min respectively, gives 673 cc/min. That's 122 hp, according to my theory

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Jets for #2300 Holley 350 cfm 2-bbl carbs:

3.7 times the estimated net hp at the flywheel gives the Total cc per minute required. Add both jets together to get the result.

Eg.1 350 cfm Holley on a little 2.0 Liter Pinto with a cam, head mods, and headers gives 130 hp at 6000 rpm. Jets needed are 56 jets, rated at 239 cc/min from another chart. (Note well. Holley and Holley Weber jets are not the same. You can't use this chart from the Holley/Weber.) The bulk flow from both jets is 478 cc/minute, or enough for 129 hp from my formula. Below this post is a long, strung out chart which shows you the flow numbers for varoius Holley jets from 40 to 100.Part of it is ex Barry Grants catalogue, those from 40 to 59 are extrapolated.

Please note that these are not stamped in thou, although that is close for the 40 to 67, after this point, the jet is much bigger inside than 100 for a 100 jet. In fact, its 128 thou.

Say you hope to have 155 hp at the flywheel of your new 200 rebuild, and you need to jet it to suit. Well, just take that 155, and times it by 3.7, and this gives 573.5 cc/min jetting required. What size jets do you need? Well, the 60 jet discharges about 285 cc/min, or 570 cc/min total. Perfect!

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Jets for #2300 Holley 500 cfm 2-bbl carbs:

5.5 times the estimated net hp at the flywheel gives the Total cc per minute required. Add both jets together to get the result.

Eg.1 500 cfm Holley on a little 2.0 Liter Pinto with a cam, head mods, and headers gives 138 hp at 6500 rpm. Jets needed from the dyno tuning session were 74 jets, rated at a massive 542 cc/min each from another chart. In actuality, thats 7.86 cc/min of jet per HP , very, very big. Too big in fact. The bulk flow from both jets is 1084 cc/minute, or enough for 197 hp from my formula. This is wrong. A couple of 66 jets, yielding 374 cc/min each, is more than adequate to compensate for a carb flow area 1.429 times larger than a 350 cfm Holley. Accordingly, the formulae has been changed to this 5.5 ratio. Anything else over sizes the jets for 500 Holleys. There is much anecdotal evidence to prove this.(Note well. Holley and Holley Weber jets are not the same. You can't use this chart from the Holley/Weber.) Below this post is a long, strung out chart which shows you the flow numbers for various Holley jets from 40 to 100. Part of it is ex Barry Grants catalogue, those from 40 to 59 are extrapolated.

Please note that these are not stamped in thou, although that is close for the 40 to 67, after this point, the jet is much bigger inside than 100 for a 100 jet. In fact, its 128 thou.

Say you hope to have 220 hp at the flywheel of your new 250 rebuild, and you need to jet it to suit. Well, just take that 220, and times it by 5.5, and this gives 1210 cc/min jetting required. What size jets do you need? Well, the 77 jet discharges about 615 cc/min, or 1230 cc/min total. Perfect for 224 hp!

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Jets for #4150/4160 Holley390 to 850 cfm 2-bbl carbs with replaceable rear jets(34-6 kit):

Formulae 1: 5.5 times the estimated net hp at the flywheel gives the Total cc per minute required. Add both jets together to get the result. (Suites 14.7:1 stoichometric ratio at wide open throttle).

Formulae 2: 6.6 times the estimated net hp at the flywheel gives the Total cc per minute required. Add both jets together to get the result. (Suites 12.5:1 maximum power ratio at wide open throttle).

Eg.1 390 cfm Holley on a little 2.3 Liter Pinto with a cam, head mods, and headers gives 135 hp at 6000 rpm. Jets needed from the dyno tuning session were two 48's for the primaries, and two 50's for the secondaries, on a 4160 carb converted to replaceable secondary jets. Taken together, thats about 178 cc/min each from the primaries, and 192 cc/min from each secondary jet, for a total or 740 cc/min. 5.5 factor, again.(Note well. Holley and Holley Weber jets are not the same. You can't use this chart from the Holley/Weber.) Below this post is a long, strung out chart which shows you the flow numbers for various Holley jets from 40 to 100. Part of it is ex Barry Grants catalogue, those from 40 to 59 are extrapolated.

Please note that these are not stamped in thou, although that is close for the 40 to 67, after this point, the jet is much bigger inside than 100 for a 100 jet. In fact, its 128 thou.

Say you hope to have 240 hp at the flywheel of your new 200 2V 250 headed rebuild, and you need to jet it to suit. Well, just take that 240, and times it by 5.5, and this gives 1320 cc/min jetting required. What size jets do you need? Well, the 330 cc/min per jet is satisfied by 62's and 65 secondaries, for 311 and 357 cc/min, or 1336 cc/min total. Perfect for 243 hp!

Eg.2 Say that someone imports an Aussie 250 x-flow, and wacks it into a Fox Mustang. He gets blown off by a 5.0 Mustang, so he decides to use a 750 Holley 4-bbl, 4-bbl intake, and works it up to spin to 7800 rpm, and hopes to get 375 hp. He jets up a 750 cfm vac sec 4160 carb, with a 34-6 kit, and finds 72 mains, and 81 secondaires are it. This, in bulk cc/min flow per hp, is 6.6 times the 375 hp figure. Bulk area of primaries is (492 + 731)*2, or 2446 cc/min. Thats about 371 hp by my formulae. In fact, this is the jetting needed for a modified street and strip 351 Cleveland 2V, making 375 hp. The premise I make is that the jetting is the same as long as the hp is the same. Fine tunning will be needed for the truth to come out.

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Chart 1:

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

Topic name change from 'Benny and the Jets' to something more sensible!

Just went through the old notes from Keith Duckworth at Cosworth. The father of the DFV/DFX/DFS V-8 racing engines.

This is where I got the carby calibration info from. On page 177 of Cosworths biography, Keith noted that FISA asked him to build a fuel flow valve for a 500 hp power limiter on a 3 liter race engine. He came up with a 27 cc/sec restrictor jet, and this was producing a 3.24 cc/min per target horspower line in the sand. If hp was to be limited to 500 hp by a restrictor plate, then a 2.086 or 53 mm plate would have done the trick, which would have yielded a 411 foot per second 'supercritical' air flow.

The make believe injector that serves 8 cylinder from one jet hasn't been made yet, but F1 bikes use 27 mm restrictors, WRC use 35 mm restrictors (565 feet per second air flow!), and NASCAR has used four 42.86 mm holes in the restrictor plate ( 210 feet per second), and it would apear that there is a clear relationship between peak power and area.

Jet flow per minute per hp fits as being the only real way to jet an engine. It all fits in to the grand scheme. It also, on a 500 hp engine flowing 27 cc/second, ties in Brake Specific Fuel Consumption (pounds of fuel per hour, per hp) into the system. Thats about 0.36 pounds per hour, per horspower BSFC if you calculate it.

So if your engine has a BSFC of 0.55, then it could be that you'll need a jet area equal to 41.25 cc/sec, or four 618 cc/min jets, to get 500 hp. That's about 5 cc/min per target horspower on an 850 cfm carb. Most of big carb engines seam rate at the 0.6 to 0.73 BSFC curve at maximum power. Little 350 cfm carb engines can run in at the 0.40 BSFC level.

I do believe that the engine at wide open throttle won't flow all the fuel in cc/minute that the charts indicate. It does depend on the signal in the carb, how much vaccum you have.

This from Falcon 64 warrants some investigation.


Note 1

took the carb. off today and found the "LIST" number along with the original IH part number stamped on it. The LIST number is 3865-2. The throttle bores are 1.5"

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Note 2

Just got off the phone with the Holley tech line. They said it is a 2300 and that it flows 260 cfm. I opened it up and found that it has #52 jets.

Is this good for my application? Do you think the jets will need to be changed?

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First thing is first. The total the carb delivers with two 53 jets is only 424 cc/minute, or 424/3.7 hp, which is in fact a puny 115 bhp SAE net from a mighty 345 Inter. That is only 150 hp gross.

Secondly, I personally know that 61's are common for 350 Holley 2-bbls, so I think it is way too low in size. I'm now going over my information

Your data may if fact be proving I' m not as crap hot on carbs as I think I am. Mustang Six (Jack) noted this too last night:-.

I've been thinking about your jet calculations and they are pretty much right on, give or take a few horses for varying Brake Specific Fuel Consumption figures, but I have a couple of observations.

On most carbs, the main jet only operates within a part throttle cruise scenario. Once the carb is tasked to provide more air, usually the vacuum drops and a power circuit opens to provide more fuel. In addition, on most carbs, the idle circuit never entirely quits passing fuel either.

If you were to block the power valve circuit on a holley, I think your figures would be correct. Of course, the carb would probably pass way more air that the main jets alone could handle.

So while your figures are correct, I think the maximum power figures available from a particular carb have to be based on more than just the main jet numbers. You'd have to look at fuel flow at the other circuits as well. For example, If you think you have 160 hp and used 68 jets, you would be rich becuase the 160 hp figure would be achieved at WOT, low vacuum, with the Power Valve also supplying fuel. (xecutes accent)

Another thing, it's possible to still miss on the jet sizing if the carb sizing is off. A carb is just a dumb fuel mixer that releases and atomizes fuel in relative proportion to the air passing thru, based mostly on velocity past the venturi. If carb sizing is significnatly off, the fuel delivery may occur on a different curve than expected. You could probably get a 200 cube six to idle with a 1000cfm dominator, but no amount of jetting would get it to run properly past that point. Imagine a 540 Ford V8 running on an Autolite 1100. Same deal. Idle could probably be achieved, but no kind of jetting would keep up with the tornado being sucked thru the carb!

Click to expand...

A few notes if you are able to cope with it. (Please bail out now if you get confused easy!).

How I did that is by this method, in which I stated that I have a 95% hit average with the formulaes posted in this link

http://fordsix.com/forum/viewtopic.php?t=8106

Below Holley 2300/2305/4150/4160/4180 jet sizes of 60, there is no data I've been able to get on absolute certainty.

What I have got is this :-

212 cc/min or 52 thou nominal, 53 call size jet

Owing to the formulae, I predict the carb delivers only 424 cc/minute, or 424/3.7, or in fact 115 bhp SAE net. Since a 260 cfm carb is small, it atomises fuel into the air stream very efficiently. Hence there is 3.7 cc.minutes discharge for each net flywheel hp. On a 750 4-bbl, its more like 6.6 cc/min per each net hp. I don't know how much extra the power valve adds to that. It could be 34 hp of enrichment at wide open throttle (two jets adding 8 call numbers to the fuel supply) .


I do know that to 53 jets cannot flow more than 500 cc per minute. I know this for a fact as some guys use jets as restrictor feeds for other equipment, and that a liquid fuel is practically incompressable, and reaches a critical speed which it cannot excead under any vaccum condition.

Further to Jack Collins statement about the issue with jetting on big engines with small carbs, I've gone over some more information to ensure that this is a correct method.

1. I could be wrong over the additinal fuel flow a power valve adds.

2. Just last night, looking at 2150 2-bbl Motorcraft carbs I found 351M 2-bbl's ran 53 thou jets on the 1978 cars, and they gave 164 hp sae net on some variants. I found the 1982 5.0GT Mustangs got 58 jets for 157 hp. And one guy, Bubba 250, got his 369 cfm 2-bl fitted out with 63 jets. All these may be different line sizes to Holley, but they look much smaller than what I've calculated for Holleys.

IS the rule of thumb to size your power valve to 1/2 your vacuum idle correct? I changed from the stock 62 to 58 and 8.5 to 6.5 on the power valve, now thinking I should have left the PV alone. Overall improvement though, it did away with the bog but now has a stumble as Jimbo described. If I ever get the rack worked out I'll check the squirter and reinstall the 8.5.

Again, consider that the main jets only provide fuel during part throttle, high vacuum cruise. At low vacuum, WOT, max HP you have all the circuits working. So 115 hp on main jets is probably consistent with 164 max hp on all circuits.

Complicating the issue is the fact that on the secondary side of some multi bbl carbs, there is no power valve, but the main jets are providing fuel in proportion to airflow.

Okefenokee Comet":22mtip62 said:

IS the rule of thumb to size your power valve to 1/2 your vacuum idle correct? I changed from the stock 62 to 58 and 8.5 to 6.5 on the power valve, now thinking I should have left the PV alone. Overall improvement though, it did away with the bog but now has a stumble as Jimbo described. If I ever get the rack worked out I'll check the squirter and reinstall the 8.5.

Click to expand...

Pretty much. The power valve should be set a 6.5 or so on any hotter six. The reason is that they carry more revs, and need to be richer than a tammer engine when the throttle opening is not so great. Remember, the power valve is a lean cruise device. If the vaccum is high, it gets shut off. If the vaccum is low the spring allows the valve to stay open;it 'spikes' the fuel flow. Technically, the 8.5 or even 10.5 is better for a fuel economy. This may mean the power valve is off all the time if your engine is seeing 8" of vaccum on an open road cruise. When you are using a lean set of jets, the power valve needs to help the carby get enriched for power at wide open throttle.

I note both you and Jimbo65 have jetted down your 200 2v/ 350 Holley combo below the 62 jet mark, and have gone back to the more conservative power valves. Clearly, the optimal jetting is much lower than the same carb on a 130 hp Pinto Four. This confuses me a good deal, but if an exhast gas analyser says it was running rich, and needed to be leaned out, then thats what you've got to do. It is very different to what other 2V guys are finding.

The only correct way to get the jetting sorted is via rolling road dyno and an exhast gas analyser. I'd be going for bigger jets, and looking at a lower 6.5 or 4.5 power valve. My friends 350 Holley ran 65's, and a 4.5. It worked pretty well on a 202 Holden with 12 port head.

I'm still running the 58 jets and 6.5 pv, thinking of installing the adjustajet I bought last year and trying a 4.5. Anyone doing it different with the 2300?

Okefenokee comet & xtaxi, I know both of you have excellent coments & jack mentioning the power valve enrichment.
I can't wait till i get my engine finished with the same carb.
The first thing to do is get your cruise air fuel correct. Try at least to get in the 13.5 to the ideal 14.5 ratio with your main jets. Then check for an off idle stumble to see if you need to richen up the accerator discharge nozzles or possibly change to a different pump cam.
After that is fine tuned see if you have a stumble on acceration from cruise mode. A higher #power valve will richen up the mixture sooner.
Get the book on holleys by dave emanual it gives you all the charteristics on the carburetor. Also the holey performance catalog give some explanation.
I plan to try my setup using 59 jet, 7.5 power valve & a .029 pump discharge nozzle. I'll fine tune from there.
Hey comet i'm still loving the sound of your borlas.
Not to bore you but my 203, using a 80 head, modified log with the 350 cfm carb-see my post on jet changes.It gives you a photo of the carb & partial intake. Im using fspp valves with the exhaust cut down to 1.430 to allow room for hardened exhaust valve seats. The bowls are extensively ported out with the valve guides shortened. using fspp 1.6 roller rockers,fspp 264 cam 214 degrees @ .050. Hooker 6601 headers 38" 1 1/2 primary pipes to dual 2 1/2 collectors. then reduced to 2" both going to a single 2 1/2 exhaust pipe to a camaro muffler then to 2 1/4 dual tail pipes. forgot to mention the valves are back cut with a 28 deg. to the lap in mark. The head is milled .075 & i plan to use the .021 steel shim head gasket. WHEW thats it. Keep us in the loop on any carb work.
I forgot to mention i'm using a 112 lobe center on the cam so the idle will be tamer. It specs out the same as a comp cam on overlap. so should idle the same as the 260 comp stick which has a 110 lobe center. :idea: : william
http://fordsix.com/forum/viewtopic.php? ... 6d4c53904f
http://fordsix.com/forum/viewtopic.php? ... 772427ff28

A lot of good reading, I didn't even realize that I had that chart on there anymore, lol

If you want maximum economy or performance, check these rules

Smallest carb total venturi area*for resonable performance:-
Cubic Inch displacement divided by 115

Best carb for performance and economy compromise:-
Cubic Inch displacement divided by 70


Best carb for maximum performance:-
Cubic Inch displacement divided by 34 to 57. Use the smaller number if engine is able to rev above 6000 rpm, use larger if engine is not likely to go above 6000 rpm

Click to expand...

* |Total V AREA| is the all up venturi area in the carb, primary plus any secondary.


The 44 carby Chronicles. All this is my opinion, hearsay, even, but it is based on feedback form people who have writen into publications like Australian and English Street Machine, Australian Wheels Magazine, Hot Rod, Popular Hod Rodding, Car Craft etc. In the fuzzy logic I work with, I've come up with these ideas on gas=flow and the Holley carb.

Theres been a lot of talk about "if my Ford Six will handle a bigger carb". Well, here's something which may help you if you are planning on a bigger Holley, possibly with more barrels.

I've done some research and found that the problem with big cams and carbs isn't the total CFM, but is in fact related to the throttle to venturi ratio, and the relative size of the primary barrels. If it has one, and the primary side of a 2-bbl or 4-bbl carb is sized small enough to suit the engines part throttle use, then the only other thing that will rain on your parade is the signal created by the shape of the carburetors venturi.

Here's the wrap. If you have a throttle area of more than 1.25 times the venturi area, you will have hassles running a long duration cam. This is because the fuel air mix fails to atomise properly due to the reversion waves, or pulses, from the intake valve. The fuel metering then gets screwed up, and the engine will back fire through the carb. In instances like this there are three options:-

1, Add more intake area or height to the intake manifold.

2, If you can back off on cam timing, do so.

3, The easiest alteration is to skim back the venturi area, so that the throttle area on the primary side is 1.06 to 1.15 times the venturi area. In other words, take the throttle diameter, divide it by 1.15 for a start, and then see if you can't fly cut the internal venturi without breaking into the carby body. If you do, just build it up with JB Weld, Epoxy, or Devcon filler, and smooth off. The jetting will need to be altered, but you will remove the propensity for spit back.

There will be situations where where the intake manifold is wrong, and nothing will fix this. Generally, if intake manifold area is about 50% of the total capacity of the engine, with no inlet tract much larger than the diameter of the throttle, then that will be a way of stopping reversion waves travelling back up to the venturi area of the carb. If it is smaller than this, the pulses can be deadened by reducing the venturi area.

Any why, heres the info to back it all up:-

Note
A. |No| is the line number of the chart,
B. |number|, the series model, not the part number.
C. |CFM| the cubic feet per minute quoted at whaever flow drop
D. |Pri B"| is the Primary throttle bore diameter in inches
E. |Pri V"| is the Primary venturi bore diameter in inches
F. |VentASQ| is the square inches of primary venturi area
G. |Signal|, the amount of intrusion of the venturi relative to the throttle diameter. Higher the %, higher the signal.
H. |Sec B"| is the secondary throttle bore diameter in inches
I. |Sec V"| is the secondary venturi bore diameter in inches
J. |Total V AREA| is the all up venturi area in the carb, primary plus secondary.
K. |Air SPD| is the actual flow speed at the cfm supplied. Maximum power happens at 200 to 300 ft/sec, so if someone has a flow rate of 488 ft/sec, then its not going to produce easy power there, and the cfm is likely to be optimistic
L. |PriBHP| is the maximum net power at 1.5"Hg for the primary ciruit
M.|Total BHP| is the maximum net power at 1.5"Hg

No|Number|CFM|Type-|Pri B"---|Pri V"-|VentASQ"|Signal%|Sec B"---|Sec V"--|Total V AREA|Air SPD--|PriBHP-|TotalBHP-| 01|#2110-|200-|1-bbl|1.4375-|1.3125|1.353“---|09.5-----|----------|---------|1.353“-------|355FT/sec|102bhp|102bhp| 02|#5200-|230-|2-bbl|1.2800-|1.0400|0.849â€￾---|23.1-----|1.4375-|1.0625----|1.736|318FT/sec|043bhp|102bhp| 03|#5210-|255-|2-bbl|1.2500-|1.0300|0.833â€￾---|21.4-----|1.6875-|1.2800----|2.120â€￾-----|289FT/sec|050bhp|113bhp| 04|#5200-|280-|2-bbl|1.2800-|1.0400|0.849â€￾---|23.1-----|1.4375-|1.0625----|1.736“-----|387FT/sec|061bhp|124bhp| 05|#6520-|280-|2-bbl|1.2800-|1.0400|0.849â€￾---|23.1-----|1.4375-|1.0625----|1.736------|387FT/sec|061bhp|124bhp| 06|#2110-|300-|1-bbl|1.4375-|1.3125|1.353"---|09.5-----|---------|------------|1.353------|532FT/sec|153bhp|153bhp| 07|#4150-|340-|2-bbl|1.4375-|1.0625--|1.7730-|35.3-|1.4375-|1.0625-|3.547--|~230ft/sec|106|213|
08|#2305-|350|2-bbl-|1.5000--|1.1875--|1.1075-|26.3-|1.500--|1.1875-|2.205--|~379ft/sec|84--|168|
09|#2300-|355|2-bbl-|1.5000--|1.1875--|2.2150-|26.3-|---------|---------|2.215--|~385ft/sec|-----|170|
10|#4150-|370|4-bbl-|1.43750-|1.0625--|1.7730-|35.3-|1.4375|1.06250-|3.547-|~250ft/sec|116|231|
11|#4150/60|390|4-bbl-|1.4375-|1.0625-|1.7730-|43.7-|1.4375|1.06250-|3.547-|~264ft/sec|122|244|
12|#4160-|450|4-bbl-|1.5000--|1.0938--|1.8979-|37.1-|1.5000|1.0938--|3.5310| ~306ft/sec|141|281|
13|#4360-|450|2-bbl-|1.3750--|1.0625--|1.7730-|29.4-|1.4375|1.1875--|3.988--|~270ft/sec|133|281|
14|#4160-|465|4-bbl-|1.5000--|1.0938--|1.8790-|37.1-|1.500-|1.0938--|3.759-|~297ft/sec|146|291|
15|#2300-|500|2-bbl-|1.6875--|1.3750--|2.9700-|22.7-|--------|----------|2.9700-|~404ft/sec|----|221|
16|#2305-|500|2-bbl-|1.6875--|1.3750--|1.4850-|22.7-|1.6875|1.3750-|1.4850-|~404ft/sec|111|221|
17*|2300-|500|2-bbl-|1.750--|1.3750--|2.9700-|27.3-|--------|----------|2.9700-|~404ft/sec|----|221|
18|#4160-|550|4-bbl-|1.5000--|1.1875--|2.2150|26.5-|1.5000-|1.2500-|4.6690-|~283ft/sec|168|344|
19|#4150/60|600|4-bbl-|1.5625--|1.25000--|2.4540|25.0-|1.5625-|1.3125-|5.1600-|~279ft/sec|183|375|
20|#4180-|600|4-bbl-|1.5625--|1.2500--|2.4540|25.0-|1.5625-|1.3125-|5.1600-|~279ft/sec|183|375|
21|#4010-|600|4-bbl-|1.5625--|1.2500--|2.4540|25.0-|1.5625-|1.3125-|5.1600-|~279ft/sec|183|375|
22|#2300-|650|2-bbl-|1.7500--|1.4375--|3.2460|21.7-|---------|---------|3.2460-|~481ft/sec|-----|288|
23|#4011-|650|4-bbl-|1.3750--|1.1560--|2.0990|18.9-|2.000--|1.3750-|5.069--|~308ft/sec|185|406|
24|#4165-|650|4-bbl-|1.3750--|1.1560--|2.0990|18.9-|2.000--|1.3750-|5.069--|~308ft/sec|185|406|
25|#4160-|660|4-bbl-|1.6875-|1.2500--|2.4540|35.0-|1.6875-|1.2500-|5.160---|~307ft/sec|-----|413|
26*|4160-|700|4-bbl-|1.6875-|1.5625--|3.8350|08.0-|1.6875-|1.5625-|7.670---|~219ft/sec|219|438|
27|#4150-|700|4-bbl-|1.6875-|1.3125--|2.7060|28.6-|1.6875-|1.3750-|5.676---|~296ft/sec|214|438|
28|#4150-|725|4-bbl-|1.6875-|1.3125--|2.7060|28.6-|1.6875-|1.3750-|5.676---|~307ft/sec|221|453|
29|#4150-|750|4-bbl-|1.6875-|1.3750--|2.9700|22.7-|1.6875-|1.3750-|6.216---|~290ft/sec|229|469|
30|#4010-|750|4-bbl-|1.6875-|1.3750--|2.9700|22.7-|1.6875-|1.3750-|6.216---|~290ft/sec|229|469|
31|#4150-|780|4-bbl-|1.6875-|1.3750--|2.9700|22.7-|1.6875-|1.3750-|6.216--|~301ft/sec|238|488|
32|#4011-|800|4-bbl-|1.3750-|1.1560--|2.0990|21.7-|2.000--|1.71875|6.739--|~285ft/sec|201|500||
33|#4150-|830|4-bbl-|1.6875-|1.5625--|3.8350|08.0-|1.6875-|1.5625--|7.670--|~260ft/sec|260|519|
34|#4150-|850|4-bbl-|1.7500-|1.5625--|3.8350|12.0-|1.750--|1.5625--|7.670--|~266ft/sec|265|531|
35|#4150-|855|4-bbl-|1.7500-|1.5625--|3.8350|12.0-|1.750--|1.5625--|7.670--|~268ft/sec|267|534|
36|#3160-|950|3-bbl-|1.7500-|1.5625--|3.8350|12.0-|1.75 x 3.625|1.5625 x 3.4375|8.682|263ft/sec|297|594|
37|#4150-|950|4-bbl-|1.7500-|1.5625--|3.8350|12.0-|1.750--|1.5625--|7.670--|~297ft/sec|297|594|
38|#4500-|1050|4-bbl-|2.000-|1.6875--|4.4731|18.5-|2.000--|1.6875--|8.946--|~282ft/sec|328|656|
39|#4500-|1150|4-bbl-|2.000-|1.8125--|5.1603|10.3-|2.000--|1.8125--|10.3206|~267ft/sec|360|719|
40|#4500-|1150|4-bbl-|2.080-|1.8125--|5.1603|14.8-|2.080--|1.8125--|10.3206|~267ft/sec|360|719|
41|#4500-|1150|4-bbl-|2.100-|1.8125--|5.1603|15.9-|2.100--|1.8125--|10.3206|~267ft/sec|360|719|
42|#4500-|1150|4-bbl-|2.130-|1.8125--|5.1603|17.5-|2.130--|1.8125--|10.3206|~267ft/sec|360|719|
43|#4500-|1150|4-bbl-|2.160-|1.8125--|5.1603|19.2-|2.160--|1.8125--|10.3206|~267ft/sec|360|719|
44|#4500-|1150|4-bbl-|2.190-|1.8125--|5.1603|20.8-|2.190--|1.8125--|10.3206|~267ft/sec|360|719|

Check with http://www.panteraclub.com/docs/carb.doc for all the gossip on all 4-barrel and even 3-barrel US carbs, including Holleys

xtaxi
I noticed in your graph a 465 4 bbl seems to have a significantly greater signal than the others of 37.1. Why is this, what does it mean.
Im curious as I have a 465 coming in the mail. Im a little worried it may not like my new cam?
Tim

That 465 will be sweet. The little 390 is used on four cylinders with big cams, and works fine. Mustangaroo and others have used it with sucess too.

#10 by xctasy » Sun Sep 12, 2004
has data that doesn't show through any longer.

Here it is reposted.

If you want maximum economy or performance, check these rules

Smallest carb total venturi area*for resonable performance:-
Cubic Inch displacement divided by 115

Best carb for performance and economy compromise:-
Cubic Inch displacement divided by 70


Best carb for maximum performance:-
Cubic Inch displacement divided by 34 to 57. Use the smaller number if engine is able to rev above 6000 rpm, use larger if engine is not likely to go above 6000 rpm

Click to expand...

* |Total V AREA| is the all up venturi area in the carb, primary plus any secondary.


The 44 carby Chronicles. All this is my opinion, hearsay, even, but it is based on feedback form people who have writen into publications like Australian and English Street Machine, Australian Wheels Magazine, Hot Rod, Popular Hod Rodding, Car Craft etc. In the fuzzy logic I work with, I've come up with these ideas on gas=flow and the Holley carb.

Theres been a lot of talk about "if my Ford Six will handle a bigger carb". Well, here's something which may help you if you are planning on a bigger Holley, possibly with more barrels.

I've done some research and found that the problem with big cams and carbs isn't the total CFM, but is in fact related to the throttle to venturi ratio, and the relative size of the primary barrels. If it has one, and the primary side of a 2-bbl or 4-bbl carb is sized small enough to suit the engines part throttle use, then the only other thing that will rain on your parade is the signal created by the shape of the carburetors venturi.

Here's the wrap. If you have a throttle area of more than 1.25 times the venturi area, you will have hassles running a long duration cam. This is because the fuel air mix fails to atomise properly due to the reversion waves, or pulses, from the intake valve. The fuel metering then gets screwed up, and the engine will back fire through the carb. In instances like this there are three options:-

1, Add more intake area or height to the intake manifold.

2, If you can back off on cam timing, do so.

3, The easiest alteration is to skim back the venturi area, so that the throttle area on the primary side is 1.06 to 1.15 times the venturi area. In other words, take the throttle diameter, divide it by 1.15 for a start, and then see if you can't fly cut the internal venturi without breaking into the carby body. If you do, just build it up with JB Weld, Epoxy, or Devcon filler, and smooth off. The jetting will need to be altered, but you will remove the propensity for spit back.

There will be situations where where the intake manifold is wrong, and nothing will fix this. Generally, if intake manifold area is about 50% of the total capacity of the engine, with no inlet tract much larger than the diameter of the throttle, then that will be a way of stopping reversion waves travelling back up to the venturi area of the carb. If it is smaller than this, the pulses can be deadened by reducing the venturi area.

Any why, heres the info to back it all up:-






Check with http://www.panteraclub.com/docs/carb.doc for all the gossip on all 4-barrel and even 3-barrel US carbs, including Holleys

A lot of great info, however you really need a wideband A/F Tester to fine tune any of the above.
Variables include air bleeds, fuel bleeds & emulsion bleeds.
A lot depends on the discharge nozzle design. Annular & like the type of nozzles on a 350 Holley.
Each one has different requirements.