is my engines carburetor or intake is too restrictive?



is my engines carburetor or intake is too restrictive?

Postby grumpyvette » March 21st, 2010, 9:37 am

thats a common question and if you think theres a need to start swapping carbs to get an answer you may be surprised at how simple it is to find the answer......carbs almost always make there best power if, the fuel pressures at between 4.5psi and 6 psi at the carb inlet,IF the fuel air ratio is between 12.4:1-12.8:1 and the vacuum in the plenum ,at wide open throttle at peak rpms is in the 1.0" of vacuum-to- 0.5" range.90% or more of selecting the correct carburetor for the application comes down to the ability of the guy using it to tune the carburetor you've selected, and set up the fuel system supplying it correctly.
you can get into the correct ball park range , for a performance 4 barrel carburetor by simply multiplying your engine displacement in cubic inches by 2.09, IE if you multiply 383 x 2.09=800 cfm
or 2.09x 454=950cfm.

keep in mind your intake manifold design, exhaust scavenging, cylinder head design, your cam timing , lift /duration/LSA and compression ratio, all effect the results youll see!, and a good indication on any restriction to flow rates is to measure the plenum vacuum under the carburetor at wide open throttle and measure the air speeds in the intake runners, but remember if the intake runners are too small in cross sectional area,or restrictive adding plenum volume, is only marginally helpful.the short version,of how a carb works,is that air velocity in the carb is what allows fuel to flow from the fuel wells into the venturi area making the carb function as designed and it takes a minimal pressure and velocity difference to allow the carb to function efficiently.
An engine, is basically an air pump, functioning on rapid increases in cylinder pressure.
Since the engine will flow a certain amount of air volume at a given RPM, use of a larger carburetor will cause a reduction in air velocity across the carbs venturi,s and a smaller carb tends to increase air velocity thus causing either a reduction in or increase in negative pressure in the venturies the airs drawn thru.
Too large a carburetor will have a reduced signal due to slower air velocity and tend to run LEAN, as its less able to instantly draw fuel thru the boosters, to small a carb restricts air flow near peak rpms..!
keep in mind if the exhaust system is not correctly scavenging the cylinders the intake is far less effective at filling the cylinders
(what goes in needs to be drawn out) and yes your almost certain to find most commercial headers are built with much shorter primary tubes than would be ideal.

YOULL FIND THESE LINKED CALCULATORS USEFUL

http://www.wallaceracing.com/runnertorquecalc.php

http://www.wallaceracing.com/lpv.php

http://www.wallaceracing.com/header_length.php

http://www.wallaceracing.com/max-rpm.php

viewtopic.php?f=55&t=858&p=3036&hilit=take+fast+ratio#p3036

http://www.wallaceracing.com/intake-runner-length.php

http://www.hipermath.com/engines/carburetor_cfm

viewtopic.php?f=55&t=1038&p=23653&hilit=test+mule#p23653

http://www.wallaceracing.com/header_length.php

http://www.wallaceracing.com/ca-calc.php

get the head intake port or intake runner to small in cross sectional area and you still get good torque and fast effective air flow port speeds but at some point the intake or heads become restrictive and power falls off as the rpms increase.
select a larger than ideal cylinder head port, larger than ideal intake manifold runner cross sectional area, and port air flow speeds drop off at lower rpms , which can noticeably reduce cylinder volumetric efficiency.
get the cam duration to short and power hits a air flow ceiling or flow limitation as the rpms increase and power is restricted.
select a cam thats got to much duration for the application and your valves close to late at lower rpms to effectively trap and compress the cylinder volume of fuel/air mix and low and mid rpm torque suffer as a result.


on any 383 sbc a good 750cfm vacuum secondary HOLLEY carburetor is going to be a decent choice, because its fairly easy to tune and theres a wide selection of power valves jets, squirters,accelerator pumps, pump cams, etc for it easily available, the fact is that a vacuum secondary carburetor is almost self adjusting to the flow required and you just need to adjust it so the fuel/air ratio stays in about the 13.5:1-14.5:1 range below about 2000rpm-3000rpm and slowly get richer too about the 12.5:1-13.2:1 range over about 3000rpm-5000rpm
you need to get the ignition timing curve correct and know how to read plugs and an infrared temp gun or fuel/air ratio meter, and a vacuum gauge can be very useful

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A bit of reading before making changes might help here

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obviously carbs with vacuum secondaries self compensate to a large degree and will allow a larger than ideal carb to still function,and run just fine, on combos the calculators may indicate need a smaller carb, thats one factor in how you can get away with using an 850cfm carb on some hotter sbc combos on the street now theres dozens of calculators available that can calculate your displacement times the rpms etc. and give you an expected carb size,
example

http://users.erols.com/srweiss/calccarb.htm

we have all seen those formulas that allow you to calculate the required carb flow rates on an engine,

CFM = engine size (cid) x maximum RPM / 3456 x VE

So, assuming 6000 RPM and 85% VE: on a 383 cid engine

383 x 6000 / 3456 x .85 = 565 CFM.

Even at 90% VE, CFM = 598

At 90% VE and 7000 RPM, CFM = 680

that indicates 650 CFM is all a stout 383 will ever need. By going to a 750cfm, you give up some better peak hp and slightly reduced throttle response due to the larger primary bores.



the formula would be just fine if the engine was 100% efficient and port flow in and out of the cylinders was at a constant air speed and the valves were not a factor, but theres a 720 degree repetitive cycle and ports generally flow only about 1/3 of that time, now divide the flow into a plenum and swap which port is running a negative vs a positive pressure about 30-60 times every second and you find true flow efficiency drops to the point where you need a good deal more potential flow capacity to match the engines requirements.
ever think of what those flow numbers mean on cylinder head flow charts, if for example the heads flow 260cfm at .600 lift and youve got 8 cylinders, it sounds like youll need almost 2100cfm of flow to keep up, but because the port only flows when the valves open and the flow rate changes with piston speed,port inertia, cam timing and exhaust scavenging,intake plenum and runner design, port reversion rates, altitude,etc. a simple formula can,t give you more than a semi-accurate guess as to the engine requirements.
the best gauge IVE found is a vacuum gauge, if your pulling more than 1 psi of vacuum at WOT your more than likely going to benefit from a larger carb or a carb spacer or a different plenum design.

viewtopic.php?f=55&t=2994

viewtopic.php?f=55&t=4362

http://www.classictruckshop.com/clubs/e ... ac/uum.htm

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but your engine may not be operating at the same volumetric efficiency levels your expecting and both your exhaust systems scavenging efficiency and your intakes flow characteristics can significantly change the expected results.
calculators will not generally compensate for factors like the differences between a dual plane and a single plane intake design ,nor will they give you a clue when you get into combos using a tunnel ram with dual quads or some other rather exotic intake or a really effective exhaust scavenging the cylinders at rates over 90% plus
but a simple vacuum gauge CONNECTED TO MANIFOLD VACUUM will be a surprisingly accurate tool providing you know how to use it.
you don,t need an expensive tool
http://www.harborfreight.com/cpi/ctaf/d ... mber=93547


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and your tach. just hook the gauge to the intakes plenum CONNECTED TO MANIFOLD VACUUM and as your running at w.o.t thru the long back stretch on your track or running thru the lights at the end of the 1/4 mile have a friend keep a close eye on the vacuum gauge , Ive found that if it reads , in the 1"-0.5" range your generally in the ball park on carb size, BUT, if you reach 0.0 even before reaching peak power and rpms your carbs more than likely to large for the application

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BTW remember those cheap crappy fuel filters I told you to never use?
well heres where they come in handy, you plug them into the rubber fuel line between the vacuum gauge and the intake plenum where they act like a pulse dampers making the vacuum needle stay a bit more steady and easier to read.
It should also be rather obvious that what goes in, needs to go out, a low restriction exhaust that reads lower than 1 psi MAX back pressure at high rpms will be required to maintain a full power curve

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http://users.erols.com/srweiss/calcdchg.htm

If you decide to go with dual quads, remember when you double the venturie area with two carbs youve effectively cut the depression, or flow thru each carb on the same engine about in half
4 barrel carbs are measured at 3", so a 500cfm carb that flows 500cfm at 3", paired with a second 500cfm rated carb would be flowing about 350cfm at 1/2 or 1.5" of depression giving the new twin carbs about 700cfm as a paired flow rate, obviously the true flow is determined by the true depression or vacuum under the venturies but the ratio will be similar
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: How do I tell if my engines carburetor is too restrictive?

Postby grumpyvette » June 4th, 2010, 8:37 am

If you need to upgrade the induction system, you can go with a larger single carb or multi carb lay out,
the question usually comes up about which is the best choice, a large dominator carb, tri-power or dual quads, if your trying to maximize your cars induction system potential, well the tri-power is not even a true option, in my opinion, they look nice, its a bit nostalgic,and it adds that old school look, but as far as performance, theres better options, sure you can make a properly set up tri-power run well! but in most cases a properly set up dual quad set-up still has some advantages , so if going the multi car route for that nostalgic look on a street car ID suggest going dual quads!
Id point out , before you go multi carb,that the single dominator on a single 4 barrel intake is by far the easiest to tune for most people, and its got plenty of power potential, but theres no denying that on a drag race engine where wide open throttle is used during easily 90% of the time that there are some advantages to the direct strait line of sight shot lay out from carb venturies to the back of the intake valve in the cylinder heads,of a well designed tunnel ram intake with twin dominators if your engine requires that amount of air flow to perform to its full potential.
you may want to keep in mind that most tri power intakes were usually dual plane designs with rather small in cross section runners, designed to get good mileage but have the option of increased air flow at wide open throttle,and that two barrel carbs are rated at 3" of mercury vacuum levels and that the center carb acts like the primaries on a 4 barrel ,but when the throttle does open enough to engage the twin end carbs its like opening 4 more venturies simultaneously or effectively jumping the air flow potential, rather suddenly by 150%-200%,as in many cases the end carbs have no idle circuit and are rated at more flow than the center carb, and when you jump from twin to six venturies the vacuum signal drops under each carb rather rapidly.

On dual quads the carb flow rates are rated at 1.5" of mercury vacuum levels, and on the street the carbs are usually set up to open progressively in 4 stages with one carbs primary pair of venturies opening slightly before the other carbs primary pair of venturies, and then the first carbs secondaries opening slightly before the other carbs secondaries pair of venturies, effectively blending 4 separate stages of increased air flow into the transition from idle to wide open throttle, and thats generally conductive to both more total air flow and a smoother transition.
either system can be made to function, but a well tuned dual quad set-up can be very responsive, while the trips are slightly more of an all or nothing set-up with very little mid transition tuning available, compared to properly set up dual quads , and theres also the option of a cross ram design with dual quads giving you the option of a larger plenum and longer runners

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you may want to play with this
http://users.erols.com/srweiss/calcdchg.htm

read these

http://www.pontiactripower.com/Tripower_Myths.html

http://www.pontiactripower.com/chevy/complete.shtml

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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: How do I tell if my engines carburetor is too restrictiv

Postby grumpyvette » October 31st, 2010, 4:47 pm

"GRUMPYVETTE? IVE GOT a tunnel ram, twin holley 950 hp's on a 700 lift solid roller 11.0:1 comp. 468 spinning just over 7000 rpm. i think it will be fine but I know there are lots of people on here with much more experience. Ive done the calculation for the cfm but i know thats only so accurate when it comes to really getting down to business. thanks in advance"


ok, first of all, a carb rated at 950cfm only flows that cfm at the rated vacuum, installing twin carbs effectively doubles the number of venturies feeding the plenum, so you've effectively reduced the vacuum a great deal.
in most cases you want the carb size USED to maintain a MINIMUM 1"-.50" vacuum IN THE PLENUM at WIDE OPEN THROTTLE , but be aware that plenum & runner design and engine displacement, may limit you to something like 1.2"-1.4" OF MERCURY and while thats restricting potential flow its not necessarily limiting your horsepower a great deal

heads are rated at 28" of water on a flow bench
Sometime during the 1950’s, engineers found that a passenger engine with a four-barrel carburetor would not maintain a vacuum of 3 inches of mercury at wide-open throttle; and by some convention 1 1/2 inches of mercury was chosen for rating 4-barrel carburetors

CFM ratings



CFM ratings are more accurate than physical carburetor sizes, as the CFM rating takes into account the venturi size of the carburetor. It is not uncommon for a given physical size (see Carburetor sizes paragraphs) to have many different internal venturi sizes. Early Stromberg and Zenith carbs could have as many as 9 different venturi sizes for a given physical size. Carburetor CFM ratings have been around since at least the 1920’s; however many O.E. (original equipment) carburetors never had published CFM ratings. I have not seen any actual agreement that stated that it had to be this way, but the early published ratings that I have seen for 1-barrel and 2-barrel carburetors were measured at 3 inches of mercury. This rating was about the amount of vacuum available on engines of the period under wide-open throttle conditions.



Sometime during the 1950’s, engineers found that a passenger engine with a four-barrel carburetor would not maintain a vacuum of 3 inches of mercury at wide-open throttle; and by some convention 1 1/2 inches of mercury was chosen for rating 4-barrel carburetors. The ratings for 1-barrel and 2-barrel carburetors were left unchanged.



To convert from one system to another (with a very small percentage of error) is relatively simple. Simply use the square root of 2 (1.414). Thus to convert a two-barrel rating into a four-barrel rating, divide the two-barrel rating by 1.414. To convert the four-barrel rating to a two-barrel rating, multiply the four-barrel rating by 1.414.



This worked very well up through the mid-1960’s, when carburetor comparison tests became popular in car magazines. One carburetor company determined that the results could be skewed by rating their carburetors “dry” (air only), instead of the conventional “wet” (a non-flamable liquid with the density property of gasoline and air mixed). Rating the carburetor dry would add approximately 8 percent to the rating (example – a carburetor rated on the four-barrel rating scale at 500 CFM would now amazingly flow 540 CFM).



As the general public was unaware of the “wet” versus “dry”, this system worked fairly well until the mid-1980’s when it seems that other scales were “needed”. No attempt will be made to explain ratings of carburetors produced after 1980. The best way to compare these units would be throttle area (which was a measurement used back in the 1950’s and 1960’s); or more accurately, the comparitive area of the main venturi. On the later carburetors, best to write to the company, and ask at what vacuum the carburetor was tested, and whether it was tested wet or dry. If this information cannot be obtained, then the rating is suspect.



So, to give an example of the 4 ratings scales prior to the mid-1980’s:



Using a Carter 4-barrel AFB carburetor that is rated wet and rated 500 CFM for an example.

To convert this rating to the 4-barrel dry scale, add 8 percent (multiply by 1.08). 500 CFM multiplied by 1.08 is 540 CFM.

To convert this rating to the 2-barrel wet scale, multiply the rating by the square root of 2. 500 CFM multiplied by 1.414 is 707 CFM.

To convert this rating to the 2-barrel dry scale, first convert to the 2-barrel wet rating as above, then add 8 percent. 707 CFM multiplied by 1.08 is 764 CFM.



Going the other direction, if we take a Rochester 2-GV carburetor that is rated wet and rated 435 CFM.

To convert this rating to the 2-barrel dry scale, add 8 percent. 435 CFM multiplied by 1.08 is 470 CFM.

To convert the rating to the 4-barrel wet scale, divide the rating by the square root of 2. 435 CFM divided by 1.414 is 308 CFM

To convert the rating to the 4-barrel dry scale, first convert to the 4-barrel wet rating as above, then add 8 percent. 308 CFM multiplied by 1.08 is 333 CFM.




http://users.erols.com/srweiss/calcdchg.htm

http://www.buicks.net/shop/reference/carb_cfm.htm

http://www.thecarburetorshop.com/Carbsh ... andCFM.htm

http://users.erols.com/srweiss/calcplv.htm
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: How do I tell if my engines carburetor is too restrictiv

Postby grumpyvette » April 28th, 2013, 10:28 am

Looking for expert advice... on selecting an intake manifold, and an explanation, if possible ? !

I've seen some recent testing with intake manifolds, usually Edelbrock Performer RPM, vs Edelbrock Victor JR. Invariably, the results being published, suggest that the dual plane is better for anything but an all out, over the top, non-streetable race engine.

I think it's a crock of propaganda.

In your opinion, given a typical, moderately civilized hot street / bracket race build... say 10:1, 2500-6500 RPm engine... what would be considered more effective ?... dual plane, or single plane ?


yes I know you probably don,t want a bunch of math and tech info, but if you really want to know how and why things work take the time to read thru the links and sub links .it basically comes down to selecting an intake that will allow you to maximize cylinder fill efficiency in the rpm range you use most of the time.
for what your describing a good performance dual plane is far more likely to provide the best results.
keep in mind, your cylinder head cross sectional area, intake runner length, cam timing, valve lift, exhaust scavenging efficiency,drive train gearing, intended operational rpm range, your intended transmission,shift points, tire diameter, car weight, fuel octane, and your engines compression ratio and displacement all effect your selection. the goal is to keep air flow rates high, to maximize the inertial ram effect and maximize volumetric efficiency, without having the runner cross sectional area,so small, it will become restrictive in the upper rpm range.

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DUAL PLANE INTAKES USUALLY HAVE A DUAL AND SMALLER TWIN, EFFECTIVE PLENUM, VOLUME, GENERALLY GOOD INDIVIDUAL RUNNER FLOW RATES AND USUALLY A CURVED RATHER IN-DIRECT SHOT AT INTAKE PORT, BUT BETTER LOW AND MID RPM VOLUMETRIC EFFICIENCY DUE TO HIGHER AVERAGE AIR FLOW SPPED
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SINGLE PLANE INTAKES USUALLY HAVE A LARGER EFFECTIVE PLENUM, VOLUME, GENERALLY BETTER INDIVIDUAL RUNNER FLOW RATES AND USUALLY A SEMI-DIRECT SHOT AT INTAKE PORT, ALLOWING BETTER UPPER RPM CYLINDER FILL RATES, BUT PORT CROSS SECTIONAL AREA,EXHAUST SCAVENGING,DISPLACEMENT, AND CAM TIMING HAVE A HUGE EFFECT ON THE INTAKE EFFICIENCY

YOULL BE AMAZED AT WHAT YOU CAN LEARN READING LINKS AND SUB LINKS
http://victorylibrary.com/mopar/intake-tech-c.htm#new

viewtopic.php?f=55&t=58

viewtopic.php?f=55&t=5510

viewtopic.php?f=55&t=8485

viewtopic.php?f=55&t=1038

http://www.hipermath.com/engines/carburetor_cfm

viewtopic.php?f=55&t=109

viewtopic.php?f=55&t=624

Been a long time.. thanks, Grumpy... though as usual, I can't pronounce most of the words you use !

You read between the lines of my question... yes, at this point, I am curious as to WHY the dyno tests that were done, comparing 3 different intake manifolds... showed the single plane to be dominant anywhere over 3300 RPM ? No, it didn't kill low / mid range.

Test engine:

All standard size, re-ringed ( pretty tired actually ! ) 1963 Chevrolet "QB" 409 short block, using ported "333" small port cylinder heads with 2.06" / 1.735" valves. Compression ratio is 10.4:1. Camshaft is a mechanical flat tappet grind, P/N M242595D, manufactured to my specs, by Comp Cams. Net left at valve, .565" / .578", 242 / 246 duration @ .050", on a 108 lobe center sep. We used a set of Belanger design headers by Wilson Header Manufacturing... 1 7/8" X 36" primaries, with 3"collector lengthened to 16".
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The numbers:

Stock intake ( dotted line ..... )
torque 438.5 @ 3500 RPM
horsepower 389.9 @ 5400 RPM ( 387.7 @ 5300, 387.6 @ 5500, 385.6 @ 5600, 383.4 @ 5700 )

Performer RPM intake ( broken line _ _ _ _ _ )
torque 448.7 @ 4200 RPM
horsepower 424.8 @ 5700 RPM ( 422.9 @ 5500, 424.3 @ 5600, 424.5 @ 5800, 423.9 @ 5900, 423.0 @ 6000, 421.8 @ 6100 )

Speed-Port 6000 intake ( solid line _______ )
torque 466.6 @ 4200 RPM
horsepower 465.8 @ 5800 RPM ( 464.8 @ 5600, 465.4 @ 5700, 465.7 5900, 465.7 @ 6000, 464.9 @ 6100, 464.4 @ 6200, 464.0 @ 6300 )





http://www.rbracing-rsr.com/runnertorquecalc.html

, your INTAKE design is not the only point of air flow restriction, if your runner size or cross sectional area is to small the design of the runners will be flow restrictive regardless of the plenum or route they take to the cylinder head port entrance, IF YOU STICK A SMALL PORT HEAD ON A 409 DISPLACEMENT ENGINE WITH 2.06" VALVES your more than likely dealing with a rather restrictive port, Id bet your not even close to the 3 square inches of cross sectional area too 3.3 square inches of cross sectional area that would be close to ideal with that cam, on a 409-454 cubic inch v8 thats expected to make power well up into the 6000rpm or higher RPM range
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if you pull the intake and measure the cylinder head and intake runners at the smallest cross sectional area on those heads youll find they are smaller than ideal.


use the link Im posting here and youll very quickly find out that the cylinder head port cross sectional area is significantly smaller than ideal for the displacement so the larger runners in the single plane helps reduce restriction, its NOT the runner or plenum design as much as the increased cross sectional area.
if you had installed a true large port runner dual plane intake you would have seen similar or better results


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a correctly designed intake can increase your volumetric efficiency noticeably, especially if matched to a correctly designed set of tuned headers and matched cam timing and compression

RELATED INFO
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viewtopic.php?f=55&t=624

viewtopic.php?f=55&t=10073&p=39779#p39779
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: How do I tell if my engines carburetor is too restrictiv

Postby grumpyvette » April 28th, 2013, 4:34 pm

OK, Grumpy... I'm with you on this... the small port heads, in bone stock form, are too small for real performance use. However, a large port dual plane ( factory or Edelbrock ), is not compatible with the small port heads. So, it's small port, to small port, to small port... ect.

Yes, the runners in the single plane are obviously larger cross section, but wouldn't that also reduce velocity at lower RPM ?

There has never been another single plane manifold for these engines, so there's nothing to compare it to.

I didn't forget the graph... but I CAN post one:

http://speed-port.ca/images/2964fa37fbac553 6d11dec...

With any luck, in about a month, we'll be testing a pretty aggressive ( hot street / drag race ) 452 inch 409 with large port heads with some work done. We'll of course be using the large port versions of the intake manifolds, hopefully a dual 4 barrel as well.



I have not built a 348 or 409 in about 20 years so just correct me if Im wrong here, but can,t you use a good epoxy filler and some port work to port match the larger port intake transition for use on the smaller port heads?
I know i build a good many big block chevy engines and some guys use the small peanut port heads , for which there are no single plane or good performance dual plane intakes , but theres several larger oval port intakes that can be modified to fit and function


Hah !... Grumpy, maybe it's about time that I fill in the blanks here

The single plane manifold used, is my own design / manufacture, which we just tested the final prototype. Reason I'm "fishing" for an explanation of sorts ( for why the single plane, in this case, annihilated a good dual plane ), is because I'm just at this moment, giving the final instructions to my pattern maker, for the runner volumes for the large port version.
Basically, the results were so astonishing, that I'm afraid to change ANYTHING. You should see the air / fuel ratio throughout the pull. The fact that the engine held within 10 ft lbs of peak torque, for 1700 consecutive RPM. The fact that it "clung" 2 horsepower of peak, for 700+ RPM.
I've driven as lot of 409's... but never a small port version that ran like this. For what it is, it's just plain BAD, all the time.

However, your comments of overcoming the anemic cylinder head, DOES offer some explanation.

When testing the large port, you have braced me for less dramatic results.

https://www.youtube.com/watch?feature=p ... ej7CwbvOUE

http://www.hipermath.com/engines/carburetor_cfm

well it seems rather obvious that you either did your home work (almost certainly the case here) or got lucky in the design and fabrication,phase (not nearly as likely) and have a very functional proto type for testing, and thats what true hot rodding is about (pushing the current limits for ever better performance.)
the fact that your power curve is showing significantly better power over most if not the entire rpm band indicates to me that the other intakes are not designed to take advantage of the longer duration cam timing in that test engine,and the ports are rather restrictive on that larger displacement engine. nor can those other intake designs supply the air flow that the engine can use with that cam, a cam that allows that smaller port head to breath much more efficiently..
you can probably get similar increased power with the larger port heads if you use a similar or slightly larger cam, with those larger port heads.
now to be fair here Id bet the original intake and the improved edelbrock intake were developed using a stock or mild performance cam, and I doubt you would see the exact same percentage of power increases with a much milder stock cam, using the single plane intake, simply because that single plane can easily out flow the other intakes as a single common plenum feeding the intake port runners is usually an advantage over two smaller plenums in a dual plane design when your dealing with a restrictive port.
thats one reason that Ive found the modified single plane oval port intakes on peanut port heads with a decent cam upgrade rather effective.
many guys think peanut port heads are only good as door stops but the truth is they can easily allow a 454-496 BBC to exceed 500 plus hp if matched to the correct components and if mildly ported.


I won't BS you, Grumpy ;) ... about 50% studying... 25% my ability to draw, and run with "that should be good", "yes, this will work", ect... and 25% lucky :rotfl:

The cam isn't really as big as it looks at a glance. VERY short seat timing... only 272 / 276 ( I'm kind of obsessive about that... I don't like lazy ramps ). Has a rough idle at about 900 RPM... I was shifting at 6500-6700 :eek: I dunno ?... It just doesn't seem to go away ?
VERY strange experience in one of these things, for sure. Heck, my Stock Eliminator engine makes around 530 HP, but it doesn't have this "never stop pulling" effect. In fact, if the test engine wasn't on it's second re-ring, with oval shaped cylinders, I'm sure we'd have seen 500 horse, with an 800 cfm carb.

Anyhow, thanks for your explanation... and not using those 12 cylinder words again ;)

Image

Image

viewtopic.php?f=55&t=6254&p=19680#p19680

Just making a few minor mods to the pattern... mostly to enhance appearance.
You know... it's a 409... it don't go fast, but it DOES look good
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: is my engines carburetor or intake is too restrictive?

Postby C_Stock_409Chevy » April 30th, 2013, 2:17 pm

Grumpy.... I'm trying to post photos of a series of dyno charts, but I have to get them on the net first.
I think the most astounding part of that test, was just how unbelievably poor the factory 409 340 HP intake is. TRULY a marvel of automotive failure :lol:
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Re: is my engines carburetor or intake is too restrictive?

Postby grumpyvette » May 1st, 2013, 9:37 am

how about you tell us some back ground info on the intake fabrication, and development process, what was required to get the manifold cast, who did it and what info or what proto type did you needed to provide to have it done?
did you need to commit to buying several hundred copys come on, a few of us have wanted to design and fabricate intakes or other engine components, and it would be very interesting to know what you went thru, as to cost, time, effort and road blocks?
I know Ive extensively modified intakes, in the past, Ive even rebuilt a few with very extensive aluminum welding and mill work,done that significantly changed it from its original configuration, but obviously either as a single, "one of a kind"or very limited production personal race car intake. " As you found out, youll sometimes find that a custom intake may not look as nice as a factory produced intake, but a proto type on a test mule may produce surprisingly better results, and you would amazed at what you can learn with a vacuum gauge, I.R. temp gun and fuel air ratio meter, and learning to read spark plugs or the improvements you can get when an intakes correctly ported and matched to a cam designed to maximize that intakes flow rates
I know I found out that simply mods like porting, and a cam swap easily gained 45-50 more hp


RELATED INFO

Image
stock un-ported runner entrances, restrict flow

Image
porting the runner entrances like this helps flow significantly

http://www.carbideselect.com/burshpescuts.php

viewtopic.php?f=55&t=431

Image

Image

below is a picture I took about 9 years ago, a very early proto type version on my test mule corvette 383 engine where I was testing cams with versions of the custom intake during research.
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: is my engines carburetor or intake is too restrictive?

Postby C_Stock_409Chevy » May 1st, 2013, 8:41 pm

Grumpy,
I was fortunate enough to be able to do the design and full scale drafting , myself.
This series of drawings was first sent to a pattern maker in Ontario, Canada.
After 1 year, and thousands of dollars, I received a completed pattern / mould.
A foundry in Alberta, was finally able to make a casting.... took 25 hours.
Pattern didn't assemble properly.
Another pattern maker in Alberta this time, turned out to be a miracle worker. He charged me another couple thousand... and actually managed to make the pattern worse.
Went to another pattern maker in British Columbia.
After 8 months, they fixed the pattern so it now works properly. Cost me me just about the total up to that date, all over again.

No one would machine it... so I bought a milling machine, and I'm doing it myself.

Pattern maker is currently making a few slight revisions that I instructed him on. ... for even more money.
New large port catings will be made by the end of the month.

I have to sell 120 of these things, and donate 300 more hours of my time, to get to the break even point of the cash invested.
With the serious setback that I had mid way through the project... I ended up continuing, ONLY because I want to save face, and my reputation.... because I said i would do it.
Was it worth it ?

not a chance
I, and my family, will live in utter poverty for the rest of our lives.
If Edelbrock decides to make a Victor JR.....
We won't even have poverty to live in !
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Re: is my engines carburetor or intake is too restrictive?

Postby grumpyvette » May 2nd, 2013, 9:52 am

ONCE you have the intakes available, in sale-able condition, I doubt youll have any problem selling them.

your experience is VERY similar to mine, Ive almost always found that most of the commercially available aftermarket performance parts could easily be improved or had obviously been designed more for ease of manufacturing than performance potential,this tends to piss me off, knowing the parts could easily be improved, About 9 years ago, I looked over the Holley steathram EFI intake when it first came out on the market, its obviously designed to be made with the minimal possible changes, to Holley existing tunnel ram, carb intake.(its a decent design but theres several ways its easily improved)
its an unfortunate fact that just having the skill and knowledge and ability required to build or fabricate the correct parts is not all thats necessary to have those parts available.
I looked it over and did a great many calculations, and fell into the mental trap of thinking simply building a much better version would be the only major thing that needed to be done, and invested about $5K in a mill, $3k in a used tig welder, plus accessories, and $2k in materials, and spent about $3200 in parts testing various cam designs
I built and tested about a dozen proto types, bought and tested over a dozen cams ,looking for a good matched combo,and in the process learned a great deal, about what makes an engine run efficiently, in the power band the intakes designed for and what mods to the intake help it work best. and while on the plus side , I improved my tig welding skills,in the process it cost me $10k to have a really good intake that performed better than the one holley sold, and also fit under a stock corvette hood line, but once I had a working, and tested intake , I used the remaining materials to knock out a couple copys, now my proto type designed easily out performed the stock holley EFI intake once all the modifications and the new plenum design and matched cam were used. I went looking for a more skilled machinist , that could produce the intakes in quantity, but no machinist I contacted and showed the proto type would agree to produce copys for anything close to a cost effective level. and I found the actual cost even without amortizing in the milling machine, and welder cost and time required was very unlikely to allow me to make anything close to a profit. so I just absorbed my losses and learned that just because I have the skill and knowledge to produce something that works really well, I also found I don,t have the financial resources required to do it commercially.
I have since greatly increased the performance potential on several advanced , and totally different versions for my own car,use, but Im no longer living in a dream were I think I can make a profit manufacturing them, so I take solace in beating the local street racing competition ,and have them give me that "DEER IN THE HEAD-LIGHTS" stare when they find I fabricated several of my custom and unique engine components
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: is my engines carburetor or intake is too restrictive?

Postby C_Stock_409Chevy » May 2nd, 2013, 5:41 pm

Geez, Grumpy... that IS similar ! ... except I'm 2 1/2 times that much money !

Super Chevy has indicated a real interest in doing an article on this. I spent HOURS communicating with Patrick Hill, nd submitted an extensive information package.
After a month, the declined.... FINALLY admitting that in their view, it would conflict with their major advertiser.

I need to get a few out there. Lamar Waldon Automotive in Georgia wants them, as does Tony Shaffer at Day Automotive in Missouri.
If I can get a few in the hands of prominent people like this, and make people happy... there shouldn't be room for another "player".
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Re: is my engines carburetor or intake is too restrictive?

Postby 87vette81big » May 3rd, 2013, 10:30 pm

C_Stock_409Chevy wrote:Geez, Grumpy... that IS similar ! ... except I'm 2 1/2 times that much money !

Super Chevy has indicated a real interest in doing an article on this. I spent HOURS communicating with Patrick Hill, nd submitted an extensive information package.
After a month, the declined.... FINALLY admitting that in their view, it would conflict with their major advertiser.

I need to get a few out there. Lamar Waldon Automotive in Georgia wants them, as does Tony Shaffer at Day Automotive in Missouri.
If I can get a few in the hands of prominent people like this, and make people happy... there shouldn't be room
for another "player".


The best advertising is not in a magazine or the internet.
Its the racetrack.
Get a few of your protype final copy intakes on a few drag and street cars. Keep in constant contact.
You have lost $, its a temporary situation.
If people win races using your single plane intake...... The word will be out.
Internet forums like Grumpys will be talking .

Briam
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Re: is my engines carburetor or intake is too restrictive?

Postby C_Stock_409Chevy » May 5th, 2013, 2:30 pm

Two problems there....
trying to get those half sozen racers to buy one.
and
going fast doesn't necesarly mean you win the silly bracket race !
( Stock / Super Stock guys do it for the chance at a heads up ! )
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Re: is my engines carburetor or intake is too restrictive?

Postby grumpyvette » May 5th, 2013, 3:30 pm

C_Stock_409Chevy wrote:Two problems there....
trying to get those half dozen racers to buy one.
and
going fast doesn't necessarily mean you win the silly bracket race !
( Stock / Super Stock guys do it for the chance at a heads up ! )


WON,t be a problem if the price is semi competitive, guys are always looking for an edge
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: is my engines carburetor or intake is too restrictive?

Postby 87vette81big » May 5th, 2013, 10:20 pm

C_Stock_409Chevy wrote:Two problems there....
trying to get those half sozen racers to buy one.
and
going fast doesn't necesarly mean you win the silly bracket race !
( Stock / Super Stock guys do it for the chance at a heads up ! )


Maybe focus on the Nostalgia Super Stock guys.
And the Nostalgia Gasser Guys.
Few of them hang out on Yellow Bullet Forum.
There are other sites those guys hang out on.
They are a tight nit group.
But they are always looking for an edge.
Down to the 100 ths of a second. 1 mph gain also.
Many refuse to use air shifters and delay boxes.
Heads up racing and 100 % driver in control.
Just like the 1950-1970s were.

Have to keep trying.
Only way to succeed . In life too.

Brian
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Re: is my engines carburetor or intake is too restrictive?

Postby C_Stock_409Chevy » May 8th, 2013, 8:49 pm

Brian...
I joined that yellow bullet forum
naah
WAY to conveluted ( spelling ? ! )... sort of like the HAMB... just too much non-specific junk.

Also joined NSS forum.
Scary, man...
99% Mopar !
A couple good 409 guys though.

Guess we'll see what happens. Everything is done at the pattern maker, and the foundry is preparig to run the first batch of castings
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Re: is my engines carburetor or intake is too restrictive?

Postby 87vette81big » May 8th, 2013, 10:45 pm

C_Stock_409Chevy wrote:Brian...
I joined that yellow bullet forum
naah
WAY to conveluted ( spelling ? ! )... sort of like the HAMB... just too much non-specific junk.

Also joined NSS forum.
Scary, man...
99% Mopar !
A couple good 409 guys though.

Guess we'll see what happens. Everything is done at the pattern maker, and the foundry is preparig to run the first batch of castings


I have to think for the next day or 2 for you.....
Last year I had a very rare Bill Cirello Frankenstein Magneto, 2nd generation about 1968- 1971 Vintage that I sold. Grumpy will remember. Less than 300 were made total. Was for a 426 Hemi Chrysler.
Old Top Fuel Dragster or Funny Car Magneto.
I advertised on the HAMB in a thread.....they got mad at me, created quite the stir up there. Yes they are a jumbled up group.
But there are a few guys always lurking there with Vintage Top Fuel Nostalgia Rails & Funny Cars.
I had guys emailing me & calling my cellphone coast to coast non stop for over 2 weeks, even at 3 am.
Texting me also.
For 13 years, everyone told me the Magneto was nothing & worthless. Deep down I just had a feeling it was very rare.
It sold for very good coin $, bought my dual axle car trailer & had $ left over.

There are a few small dedicated forums for the racers I stumbled across in the past, like Super Stock 409 guys.
I believe the market is there for you.
Just getting the word out.
Still think using 1 of your intakes on a succesfull 409 Racers race car one of the best way to get the word out.

The problem with Yellow Bullet is all the crazies there.
Just like a real NHRA Race Track on a Sunday Summer afternoon. ;)
There are a few very smart guys posting there time to time.
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