I don't know of a source for those parts.  The power valve can be disabled by clipping off the actuating stem of the diaphragm, but there is very limited adjustment capability of the accelerating pump.  Clipping the stem will leave the PV closed all the time.

John - "The Hoosier Hurricane"

Is there a source for assorted power valves for these? How about secondary tubes? I recall a friend of mine talking about eleminating the power valve on the flat bowel Holley's and making accelerator pump adjustments to compensate but I do not remember exactly what he said. He just put in a plug.

The teapot power valves are nothing like the later Holley ones.   The teapot ones are a brass valve in the bottom of the fuel bowl, acturated from above by a stem on a diaphragm.  The spring on the stem holds the valve open, the vacuum on the diaphragm allows the valve to close.

John - "The Hoosier Hurricane"

I set mine up from the Hot Rod Magazine Ford Pefromance Handbook printed in 1962. Their dual quad carb recomendation based on dyno tuning was .048 primaries and .055 secondaries with the float level set at 1/2 inch from the top of the float bowl to the gas level with the engine running. No power valve recomendation was given. This is right where the Holly specifications were. I am wondering if I need to step up the primary jetting with todays fuels? The primary jets are standard holly but the .055 secondary tubes were hell to find in 1965. Does any one know of a source today? I also have a question on the power valves. Are these standard Holley power valves that are available today? I have always used the ones that came with the carb kits and that could be a problem. This has been a great source of info for those of us still running the E carb setup. I appreciate all the info.

I"m sure you know of the existance of the 56 Ford dual quad setup using the Teapots.

Holly factory specs on the 56 dual quad carbs are #48 jets for the primarys and #55 for the secondarys .

Now the same carbs were used on the Mercury M 260 dual quad setup.I have a Mercury service letter that says to install #49 main jets in place of the existing # 44 jets.

So thats a bit confusing since according to Holly there were no #44 jets used.

Take it for what its worth.Hope this is helpful.

Oldmics

Me-I"m gonna jet the crap outta my twin teapots to accomidate the cam. and see what happens

As pointed out, the dual quad Holley teapots had several differences from the '56 Holley single quad units. On the '57 dual quads, for operating from 0 to 15,000 ft. elevation, the factory numbers were:

- Main jets #45

- Secondary metering tubes #55

- Power valves #32



My '56 single quad carbs came with #50 main jets, #73 metering tubes, and #28 power valves. While going with the dual quad jetting numbers may not be perfect depending on an engine's displacement, camshaft, etc. it should provide a reasonable starting point for sorting things out. I'm scratching my head regarding the difference in secondary metering tube sizes.



IF anyone has suggestions regarding jetting the '56 teapot carbs for use in tandem, Slumlord and I are interested.



Information in previous Forum threads from Ted and others regarding modifications to power valves, vacuum diaphragm springs, use of a balancing tube, and things to be careful about when rebuilding the Holley teapots have been GREATLY appreciated.



This forum is invaluable to me as I effort to assemble y-block combinations without a lot of trial, error, and frustration. THANKS to ALL for their contributions of time, information, and hard-knocks experiences. APPRECIATED!

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

slumlord444 (12/13/2011)

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As I recall I saw flow figures on the dual quad carbs a long time ago and they were 350 CFM. That sounds realistic considering they made a 500 cfm 2 barrel. That comes to 700 cfm. I am thinking even if they were only 300 cfm that adds up to 600 cfm. I can see where the better 4 barrel manifold would be better but I doubt the numbers. I am wondering what the jetting was in the dual quads? Both sets of original dual quad carbs that I have had '56 Ford single quad jets in them when I got them. Way too rich.

The comparision chart only shows the dual quad setup going to slighly under 6000 rpm. Mine goes to 6500 with no problem and has gone to 7000.

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When dyno testing, it’s typically only performed to the point just past peak power being made.  Any more than this simply stresses the engine although it’s capable of considerably more rpms.

Regarding the richness of the single 4V Teapot carbs being used on a 2X4 intake, the power valve actuation springs must be modified.  With dual quads, the vacuum signal to each carb is essentially cut in half and this is enough to keep the single quad power valves from closing at idle with any kind of performance camshaft being used.  The power valve springs and diaphragm that come with the new carb  kits are designed for single quad use and not dual quad use.  Hence the need to modify the tiny ‘ball point pen’ springs on the new units before they are installed in the carbs.  And then if you want the secondaries to open at the factory specified rpms, the spring tension in the secondary diaphragms must also be reduced.  That same ‘half vacuum signal’ scenario plays in with this also.  The long yellow springs supplied in the Holley spring kits is a good starting point for this.

While camshaft and valve springs will ultimately dictate what the valve train limitations will be, where the peak horsepower and torque numbers actually come into play can be determined by a variety of other factors.  It’s one thing for an engine to be able to twist past 7000 rpms but entirely another for it to make good power numbers at that same rpm.  The 2009 EMC Y engine was twisted repeatedly at the Engine Masters Challenge to 7400-7500 rpms but the power numbers fell like a rock after 6500 rpms.  This was an engine that still required significantly more air flow than was being supplied by the fully ported 113 heads that were on it.  The aluminum heads cured that issue in the 2010 EMC competition.

As the cubic inches goes up, so does the air flow requirement to maintain the power increases in the upper rpm band.  If the overall air flow is not correspondingly upsized along with the cubic inches, then the flow becomes more restricted as the rpms do go up.  In these instances, the torque numbers increase at a lower rpm but the horsepower drops off earlier in the rpm band.  If increasing the head flow, then the intake flow must at least match the head flow but this is typically at the cost of some of the lower rpm band torque numbers.  In those instances where the intake manifold and/or carburetor are matched closely to the stock head flow, then porting the heads where they flow considerably more will not see the same improvements as using intakes that also flow appropriately more.  There will be an improvement but not near as much as if the whole system is ‘balanced’ or matched throughout.

But back to the main question.  The aluminum heads simply require an intake and carburetor combination that matches the air flow requirements in the upper rpm’s.  For this I’ve reposted the HP graph below.  Up to 4300 rpms, the 2X4 intake and the Mummert 4V intake are similar in HP values.  It’s after 4300 rpms that the Mummert intake on the aluminum heads starts to run away from the 2X4 intake.  It’s not that the 2X4 intake is all that bad, it just that the Mummert intake and 750 carb that were being used are just that good.  Had a pair of carbs with more cfm capability been used on the 2X4 intake with the aluminum heads, I suspect the HP values would have been closer.  Keep in mind that the original 2X4 carbs that were used in this test are smaller in cfm than the standard run of the mill Teapot carbs that are used on the single four barrel applications.  Those original carbs were suitably matched to the factory heads and camshaft as well as ‘just’ 312 cubic inches.

 

Lorena, Texas (South of Waco)

I don't see where engine size has anything to do with how many rpms the engine will turn. That would be determined by the camshaft and valve springs. Still wonder what the jetting was on the dyno test dual quads. My manifold has had the ports matched to the heads using the intake gasket as a guide. I am assuming this helps flow somewhat. Still can't see the 45 horse loss with the dual quads. I know when I canged out my original factory single 4 barrel to the dual quad setup the improvement was not near 45 horses.

Guys: As I recall the article, Karol Miller ended up reving the engine to 7200 rpm, not because it made more power there, but because of the amount of drop off on gear changes.

Paul

The build and size of the engine will come into play so that chart can't really be used to determine maximum rpm potential for anything other than that engine. What may rev to 7000rpm on one engine may not on another. I believe Karol Miller's Bonneville Ford was reved to 7200 with 2-4s.


Lawrenceville, GA