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.

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.

Charlie has it right on the heads in regards to determining how much they have been milled. Any measurement less than 1.000” at those pads will give an approximation on how much the heads have been 'flat' milled.

Jeff. The brass tubes within the throttle bores sees the manifold pressure (vacuum) via a passage that’s drilled width wise at the bottom of the carburetor. Those tubes being in the throttle bores at an angle boosts the negative pressure signal at the fuel discharge nozzles when the throttles are opened just beyond the idle position. This would have been Holley’s answer for that time period for a transition circuit or a way to get some extra fuel to the engine between the idle and high speed circuits. On the Holley 4150/4160 carbs, this is accomplished with slots in the throttle bores that would allow an extra amount of idle fuel into the engine when the throttles are opened up slightly. On the model 4000 Holleys (Teapots), that extra amount of fuel is by way of an earlier discharge from the high speed fuel circuit which also helps to prevent an off idle stumble.

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The brass tubes were likely not needed on the dual quad carbs due to the brass rings on the boosters which by themselves increases the air flow through the venturies at the lower rpms. The original purpose of the brass rings was for a cfm reduction in the carbs which makes them more responsive at the lower rpms. That increase in air flow also promotes an earlier discharge from the main fuel circuit which makes the brass tubes that were standard fare on the larger Teapots no longer needed. But a secondary reason for getting rid of those internal brass tubes was that they were simply in the way of the brass rings on the atomization nozzles found in the factory dual quad carbs.

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Here’s a picture of the bottom of a non dual-quad Holley model 4000 carb showing the ‘crossways’ drilled passage that allows the vacuum signal below the throttle blades to be transferred to the brass tubes going up to the primary venturies.

The main detriment to the Holley model 4000 4V carbs is the single needle seat design which simply limits the amount of fuel that can be supplied to the carb. On 400 or more horsepower, it’s difficult to keep the fuel bowl full through that single needle seat. With horsepower levels steadily going up, the introduction of the Holley model 4150s’s in 1957 was Holley’s answer to the fuel supply issue. The transition between the idle and high speed circuits was also improved. The Carter and Rochester 4V carbs of the time already incorporated a two inlet fuel design (two needle seats) and so they were ahead of the curve at the time.

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For the pistons, I believe this is the post you’re looking for.

http://forums.y-blocksforever.com/FindPost88522.aspx

Jeff. While any custom piston manufacturer can make pistons to your specifications, I use either Diamond or Wiseco for the Y-Block stuff.

Wayne. It was the ’56 Merc Carter WCFB carbs that were tested. There were no ’57 Lincoln carbs available at the time of the tests but some of the mid-Fifties Carters from GM engines were tested and those did have larger venturies than the Merc carbs. The GM Carter carbs (WCFB’s) ran close to the same performance numbers as the Lincoln Teapots but those carbs also had the same carburetor base flange as the Teapots and ’56 Merc WCFB carbs. I’m guessing that the ’57 Lincoln Carter carb is the AFB version and not the earlier WCFB version?