Has anyone experimented using the '56 Lincoln carburetors as dual quads? What size jets are recommended for the primaries and secondaries? I have two Lincoln carbs that I'm currently rebuilding and modifying to dual quad status. #55's are used for the primaries in one carb. while #59's are used in the other. which ones are correct for the stock Lincoln? #96's are used in both carbs for there secondaries. I'm pretty certain that #43's are used as the primaries and #55's for the secondaires on the authentic dual quad ECJ 9510 AA or AB carbs. What sizes would work best with the Lincolns?

Jeff P.s. thanks to all for the help.....it's most appreciated

If you get the Y-Block Magazine, then issues #115 & 116 went into detail on dyno testing of the various dual quad intakes where different pairs of Lincoln Teapots were also in the mix. For the List #1094-1 carbs, the primary jets were happy at #60 and secondary jets at #82. For the List #1094-4 carbs, primary jets were #57 and secondary jets were #82. I don’t recall the power valve numbers off hand as they are also players on the primary jetting side. That information is here but currently buried.

Lorena, Texas (South of Waco)

Hi Ted,

thank you for the quick response and the very helpful info. I was thinking you or someone else would respond and say it's too much carburetion for the 312 engine. I'm using the original '57 ECG aluminum intake. Is this acceptable to use with the jets you mentioned and the Lincoln carburetors? I, really want to keep the set up as stock as possible. I'm working on the Carb bases and have made vacuum ports (under the fuel inlet at the rear uses a 1/4" pipe thread) as if the Lincoln carbs were the 1956 ECZ Carbs (or the actual dual quad carb ECJ 9510 AA-AB). I, put in the balance tubes, put in the small 1/8th diam. plugs for the Right side secondarys. (I, believe it's a plug and not a tube?) I'm getting aluminum plugs made to block off and seal the hole where the spark control valve would go. Removed the brass idle tubes in the primary venturies (I, believe there called idle tubes?) Ted, I, don't mean to make this a long drawn out message :-) The job is a little bit intricate and like running through the steps that I've taken to some one more knowledgeable like yourself. Unfortunately I don't get the y-block Mag. that you mentioned. If you do come across the the power valve # that I, should be using that would be great.....I, know I have more changes to make the Lincoln's. While I'm thinking of it.....Is it necessary to have the #58 type air horns (fuel bowl cover) like the actual ecj 9510 aa-ab carbs? It's hard to describe through text but how do the larger circles on the #58 covers matter? I, believe the Lincoln's are #48's? and the same for the ECZ 1956 carbs...I, got a little bit long winded on this mssag....Lol.

Thank you you again for the info and the interest

Best Regards,

Jeff Abate

The original 57 Holley 4000 Dual Quads use smaller power valves than the original single quad applications. The larger power valves cause the engine to bog.

Paul J. - '57 E Code

Personally I have found that jetting is pretty close from one carb to another but what I found was if I put it on an engine of higher compression a change was needed. The stock jetting was to the ventuii size and the compression and not as much relevant to cubic inches all things being equal.

Bigger carbs have bigger venturiis so a larger jet is needed to compensate for the increase in air to keep at the prescribed ratio of fuel to air. When I would raise comp ratio it would then be lean and I would change jetting.

As an example I use a 331 1953 Cadillac Carter WCFB on my 1956 292 small base. The Cadillac comp ratio is 8.25 and the Ford is 8.4 and it runs great with no changes. Exhaust is clean and the plugs do not soot up with mostly city driving.

After market carbs today are set for what would be the norm in compression 8 thru 9 to 1 and you need to keep an eye on the plugs pretty quickly after installation......Good Luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Thank you for your input on helping me keep the CFM in perspective to engine displaclement. And actuality one doesn't have a lot to do with the other. I, understand what your saying that the cfm is greater in a particular carburetor and this demands an increase in the jets.....I, need to figure out what size power valves I, need? Ted Eaton Got me on track with the primary and secondary jets.....So I'm off to a good start....I, appreciate everyone's input and support.....Haven't put them back together yet....Need to clean parts, order another reb. kit with sec. diaph. and finish the conversion..... thanks again for the help

Jeff

Thanks Paul,

Your helping me get a better perspective on how the Carbs work and the reasons why Holley did what they did to make them work properly......What do you think would happen if I, used to small of a power valve? Was #33 the correct one for the Orig. dual quad? I, can't remember?

Jeff

Didn't mean to repeat what you just explained to me....just wanted you to know that I, get what your saying on CFM and compression ratios.....and how changes maybe needed? I'm running some where around 9.1 to to 1 Might be slightly higher?

Jeff

The aforementioned dual quad testing was performed on a +060 over 312 that uses an older Crower 238° @ 050”camshaft. Depending upon the heads being used, the static cr is 9.1-9.6:1. This particular short block would have been a pretty typical build for many of the performance Y builds in the 50’s & 60’s. The Lincoln T-Pots on this engine did outperform both the factory dual quad carbs (which included both List 1268’s and 1434’s) and a pair of modified List 1161’s in most instances so over-carburetion with the Lincoln Teapots on this particular combination is not an issue. Port work on the intakes is always a big help as the HP numbers with ported intakes really takes off with the larger carbs.

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The fuel bowl covers on both sets of Lincoln carbs used in the dual quad testing are #48's. As delivered from the factory, those covers contain air bleed holes that are sized as per application. On the Teapot dual quad applications, it’s important that the same ‘numbered’ covers be used on each carb. By using the wide band oxygen sensors on the dyno, the fuel curve throughout the rpm range can be evaluated and modified as deemed appropriate. The key here is having a fuel curve that’s consistent throughout the rpm range and not lean on one end and rich on the other. Swapping covers can alter the idle and/or high speed fuel mixtures depending upon the bleed hole sizes. Cover changes by number are a quick way to do this once the various hole sizes are measured. To do this you’d need a stack of the various covers in lieu of either soldering up holes and redrilling or making the existing holes larger.

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If the brass tubes to which you refer are the tubes that protrude from the bottom of some of the Teapot covers, those are necessary to richen up the high speed circuit. Removing them may cause a serious off idle stumble while also creating a lean condition jetting changes cannot fix. I’ve found that the idle bleed holes in the Lincoln Teapots are on the large side when using them as pairs on the smaller cubic inch Y’s. Sticking various sizes of small diameter wire in those holes on both carbs while running the engine at idle helps to determine exactly what hole size is ultimately needed for the idle mixture. With the right size idle bleed hole in place, the idle mixture screws are happy at ~1 turn off of closed.

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As a general rule, whatever jets are correct for a single four barrel application will be too large for the same carbs when used as pairs. This is simply due to the reduction in cfm that takes place through each carb when using them as pairs. The larger the carbs, the more sensitive they are to jet changes. For the optimum air/fuel ratio when switching single four barrel carbs to dual quad pairs, the jet sizes in both the primaries and secondaries are reduced accordingly. Otherwise the carbs tend to run on the rich side.

Lorena, Texas (South of Waco)

Hi Ted,

The tubes that I'm referring to are the ones in the primary venturi's found on the ECZ 1956 holley 4000 teapot carbs. They come up from the bottom and are at an angle. These are not present on the ECJ 9510 AA or AB dual quad carburetors. To help some-up what I'm doing....I'm converting the Lincoln Carbs, To match the original Dual quad Characteristics. I, hope I'm correct in doing so for proper running.....e.g. I, installed the balance tubes. Making a plug for the spark control ports, etc. If i'm understanding you correctly on the "air horn or "lid" of the carburetors the #48 air horns are ok to run as a pair? Thank you for your time in explanation and research you've done.....Honestly some of it is a little over my head....

I'm running a 312 engine .030 over ECZ-G heads. .005 milled off both decks, Heads were milled by someone before I, bought them. The person milled enough off of them to where they started to cut into the lettering that's cast into the head surf. It, could be .020 to .030 milled? You probably have better other standing as to how much? I, run the M-260 cam. .434 lift 268 degrees of Duration (this is what was printed on the grind card) I'm currently running with the factory orig. dual quad set-up no problems.....just wanted to try something else... Curious to hear your thoughts and imput....

Jeff