[Tom Vaught]

I like your "assumed" answer much better vs the float sticking/ carb flooding one.

Most idle feed restrictions are in the .035" range and we know that you can move a bunch of idle fuel through that orifice size which is only .007" bigger vs the .027" air orifice you are describing. You could get a lot more air (vapor) thru those holes than most people think. A flooded carb with fuel pouring out of the booster though is a bit of a stretch as far as fuel passage.

Tom V.

[Doug]

I'm enjoying this discussion so I thought I would offer some things to think about.

First off, the "bore" of the base plate on my '66 end carb is 1 11/16" (nominal) diameter. Since it is a "cylindrical bore" and the throttle plate when closed sits at an angle of about 10 or 12 degrees or so to the bore when it is closed, the plate is actually an elliptical shape instead of being a circular one.

The half of the plate that points "down" when closed has the 0.027" (so called) hole in the plate about 3/8" from the edge of the plate and when the plate is closed, it creates a small pocket where a small amount of fluid could accumulate (at least in theory).

The 0.027" diameter plate "hole" calculates to be 0.000572557 square inches in area.

The circumference of the plate is (disregarding the ellipse vs circle shape) 5.30145 inches.

We all have heard that if you can see any daylight around your throttle plates when closed, you need to make repairs.

So, I did a little math and compared the area of the 0.027" hole to an "equal area" around the circumference of the throttle plate. It turns out the 0.027" hole is equal to having a 0.000108" wide "leak" around the plate.

When I hold up my baseplate and look for daylight around the plate, how much does a 0.000108" wide "leak" look like?. Maybe it's easier to plug the 0.027" hole than wear yourself out overhauling a carb.

And, I don't believe there is any tri-power driver that can refrain from nibbling on the end carbs every time he is out on the road.

P.S. There's still those darned throttle plate shafts that leak. (Hmmmmm?)

[Dick Boneske]

Good comments, Doug. After thinking about this subject for quite a few years, I believe the main function of the holes was to ensure fuel circulation in the end carbs without a detrimental effect on idle quality. We all know how badly a small gap around the throttle plates affects idle. With many I've rebuilt, DAG 213 was the only way to eliminate this gap.

According to feedback from members, these holes were used only in 1964-1966.

[Tom Vaught]

Originally Posted by Dick Boneske

Good comments, Doug. After thinking about this subject for quite a few years, I believe the main function of the holes was to ensure fuel circulation in the end carbs without a detrimental effect on idle quality. We all know how badly a small gap around the throttle plates affects idle. With many I've rebuilt, DAG 213 was the only way to eliminate this gap.

According to feedback from members, these holes were used only in 1964-1966.

So where would the fuel for the front and rear blade holes be coming from Dick? I assume you are not referring to the center carb based on the statement above.

The front and rear carbs have no idle circuits, No Power valve circuits, etc.

Help me understand where the fuel is from that passes thru those holes at idle. The pump circuit and main circuit is not on at idle.
(Not a criticism, just a question).

Tom V.

[Dick Boneske]

Tom, your point is exactly correct. However, in actual operation, there is always SOME amount of dampness--gas--in the venturi area. I don't know if it comes from splashing in the float bowl that allows a few drops to drip from the nozzles or where it comes from.

By the way, this is on a setup with near-perfect throttle plate fit--no .027 holes.

What do you think?

[Tom Vaught]

On a holley carb without a Vent Whistle, if a guy put the brakes on hard after a spirited acceleration you could get fuel out of the vent tube and into the venturi/throttle plate area.

The Rochester 2 BBLs having the vent in the roof of the carb lid would make fuel from the bowl migrating into the throttle blade area more difficult.

I agree totally with you that your experience says there is fuel in that area.
I was hoping you could help me understand where it was coming from.

Fuel pull-over from the shooters happens occasionally on the holley carbs which is why most use a fairly heavy needle vs a ball like the Rochester stuff. The ball is at the lower part of the carb pump well so maybe enough fuel is above the ball that it migrates out the shooter at times. Just thinking out loud as I type.

Tom V.