Ted, the brass tubes are actually pressed into the primary veturies. As mentioned before they come in at an angle from the bottom-up. There actually pressed into the side walls of the venturies at an angle. Holley omitted them on the factory dual quads for a reason....not sure why? Don't know what they do? the part that's confusing is the tubes "lead" to the base of the carb. The holes get covered up when mounted on the intake. This would only leave the brass tube open at that end?

Thanks again for the help and explanation

Jeff

This is a bit of a bunny trail from your carburetor questions, Jeff.

My understanding is that the pads located below the cylinder head exhaust ports, adjacent to the cylinder head surface area that mates with the cylinder block... those pads were 1.000 inch thick when new from the factory.

Sooo... if you measure the thickness of your pads, you'll know how much each cylinder head has been milled over time.

Hope this helps.

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

Actually the area is in the machined surface of the head.....I'm not sure but I, think it might have ecz there? Not to be confused with the corners of the head that are visible with the heads installed. ECZ-G

Jeff

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.

Lorena, Texas (South of Waco)

I'm aware of how ford claimed to have made there "machined" thickness blocks and how they made it so that the thickness could be determined. I, found it to be inaccurate. I, measured heads that were machined verses one that I, felt were not. Never felt like I, came up with a confident # with the different heads I, measured. I, work in a machine shop on diesel engines. In some instances the manufacturer (caterpillar) would mill the coil spring seat area and then you could use a depth mic with a strait edge on the deck surface. ....Unfortunately there is nothing machined on the valve cover side of the y-block cylinder heads. Ted, you probably have a lot more experience with the y-blocks then I , have but I, never felt confident with fords way of measuring cylinder head deck thickness

Jeff

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.

.

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.

.

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.

Lorena, Texas (South of Waco)

Hi Ted,

I appreciate your efforts in helping me to understand why Holley did the changes and modifications to the e-code carbs. Along with that just being able to understand the functions of the teapot Carburetor..... Unfortunately there aren't many people out there that know a lot about them and the Ignorant one's replace then with Edelbrock units and the like. I admit they are a little intimidating cause quite frankly few people know how they work! Walt Nuckles was a guy who knew a lot about the Carbs and Y-blocks and unfortunately has been deceased for about 15yrs. now. He also was from Texas. If you have the chance.....could u put the photos of the different semi spherical pistons as an option for using the "G" heads with the Supercharged engines. You had put these pictures on a month or so ago when I was asking about supercharging an engine....I, tried to find the photos but can't seem to find them?

Thank you again for your help n interest

Jeff

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.

.

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

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

Lorena, Texas (South of Waco)

Hi Ted,

Thank you for the explanation as to why the Teapot was replaced and thanks for finding me the link on the pistons....Very cool.... :-)

Thanks so much n Best Regards,

Jeff abate.... P.s. If you needed to have a set of Pistons made with the semispherical design...where

would you send them?

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

Lorena, Texas (South of Waco)