Webber Transition Ports

[Bill Cuthbertso]

Instead of drilling a third hole, has anybody tried opening up the original two holes to equal the volume of three as if the third hole was added? This would eliminate the need for a jig. It seems that this could be done on the car by coating the drill bit with some sticky grease to capture the chips. I think that any of the very small chips that happen to enter the cylinders would be vaporized with no damage being done. What do you think?

[zimmy]

Bill:

I think you have missed the point of the third transition hole. It isn't to increase the volume of mixture available, it is the position of the hole that helps. The third hole is positioned just above the upper hole so that it becomes enabled as the throttle plate continues to open. By adding the third hole, you extend the transition circuit by increasing the flow of the transition circuits for a longer period of time as the throttle opens.

[Bill Cuthbertso]

zimmy,
Thanks, makes sense, however the volume of fuel must also increase but I will abandon the idea of enlarging. Is it absolutly critical (as others have stated) that the holes are placed exactly at the same spot an all carbs? If so what does the drill jig look like?
Bill

[dlampe]

That is a good question. If someone has this jig, maybe we could pass it around with a deposit so we could make these modifications.

[Rick Parker]

I have heard of the tool being a piece of brass round stock that had a very small tight tolerance hole drilled off center in it lengthwise. It is inserted in the port after the threaded brass plug is removed, the hole is clocked to particular position (12 o'clock?) and then a correctly sized drill is inserted in the hole and then by using a pin vise twisted with your fingers you create the new hole through very thin metal in the carb bore.

Having access to a Bridgeport Mill would also allow the hole to be very accurately located.

[Gaz64]

Originally Posted by Rick Parker

I have heard of the tool being a piece of brass round stock that had a very small tight tolerance hole drilled off center in it lengthwise. It is inserted in the port after the threaded brass plug is removed, the hole is clocked to particular position (12 o'clock?) and then a correctly sized drill is inserted in the hole and then by using a pin vise twisted with your fingers you create the new hole through very thin metal in the carb bore.

Having access to a Bridgeport Mill would also allow the hole to be very accurately located.

Yes, I'd agree with your thinking Rick, but I'd make it of steel (tool steel if possible) the harder the better, less chance of the drill wearing the hole after repeated use.

Some form of saddle clamp around it and tying it to the base of the carb would be solid enough.

Only Mr. Weber will ever know why he released IDAs with only two progression holes.

The are 4 and 5 hole DCOE carbs now.

[Rick Parker]

They were first designed I believe for the Porsche Carrera 4 1600 CC double OHC engine used in the RSK Spyder and 356. They were intended to be used in a race environment; transition was not given a lot consideration.
They are now used in many applications for which they were not intended.

[Bill Cuthbertso]

Made the jig, threaded some brass round stock, drilled .039" hole off center, screwed into port, locked at 12 o'clock with locknut, drilled hole through carburetor bore, done!
Didn't even take carbs off of the engine. stuffed a rag with a small amount of grease on it down the carb bore. drilled the hole and of course most if not all of the chips came away from the internals. Used a special aluminum magnet (Q-tip with grease on it) to gather up the chips. These pieces of alum are so tiny that I think if any did make their way into the combustion chamber they would be vaporized and would cause no damage.
Definitely improved the mid range driveability.

[carmine]

Hello Bill

How about posting some pics of the new hole and drill tool quide
you made up

Pictures worth 1000 words

Thanks Carmine

[Rick Parker]

Bill:



How far off center was the hole drilled or did you just "Eyeball it"?

[Bill Cuthbertso]

I do realize this is a really crappie pict but it's the best I can do.
This is a picture of one guide disassembled and one assembled as it would go into the carb. It can be locked into any position you desire, I set my third hole at 12 o'clock. If you make the jig, I would suggest using a one millemeter new HSS bit of good quality as this will reduce the tendency to wander off center. The threads are 7mm x 1.0.
These modifications were done for a 2332 cc opposed four cylinder engine.
Hole is 2/32 ( 1/16 for the mathamatically challanged).
off center, overall all length is 15/16.

[ENTDOC]

gotta admire a guy that takes the bull by the horns and gets the job done

[Earl J]

Originally Posted by Bill Cuthbertso

Made the jig, threaded some brass round stock, drilled .039" hole off center, screwed into port, locked at 12 o'clock with locknut, drilled hole through carburetor bore, done!
Didn't even take carbs off of the engine. stuffed a rag with a small amount of grease on it down the carb bore. drilled the hole and of course most if not all of the chips came away from the internals. Used a special aluminum magnet (Q-tip with grease on it) to gather up the chips. These pieces of alum are so tiny that I think if any did make their way into the combustion chamber they would be vaporized and would cause no damage.
Definitely improved the mid range driveability.

Hello Bill,

Great job! I do have a question is this item for sale or rent? I’m also curious to know if it’s possible to add the other two holes to the tool so when one aligns the 2 existing holes with the tool, the placement of the third hole would be symmetrical instead of eyeballing the third hole to the 12 o’clock position going from carb to carb. Just a suggestion.

Thanks,

[carmine]

Does anyone know if 12 oclock is the correct position to drill the 3rd progression hole.

[Bill Cuthbertso]

I really think that there is no really correct position for the third hole. I think that the upper area is a convenient place to put the hole because there is alot of room.
If you turn carburetor upsike down and watch the butterflies open, you will see that the progression holes are not opened in sequence. All three are open to the vacume at the same time so I do not think it matters to much if at all. The size of the hole certainly does matter. 12 o'clock seemed to work for me, but I think 2 o'clock will also work. I used 12 because it was easy to eyeball that location from carb to carb.
Lets hear your thoughts.

[Jac Mac]

Has anyone ever considered simply joining the 1st & second holes to form a slot similar to a Holley & then extend that slot up toward the choke/venturi rather than drilling a 3rd/4th hole?

[Bill Cuthbertso]

Originally Posted by Earl J

Hello Bill,

Great job! I do have a question is this item for sale or rent? I’m also curious to know if it’s possible to add the other two holes to the tool so when one aligns the 2 existing holes with the tool, the placement of the third hole would be symmetrical instead of eyeballing the third hole to the 12 o’clock position going from carb to carb. Just a suggestion.

Thanks,

Earl,
In a perfect world we would assume the factory holes are all in the exact same position and they may well be, however I have seen other "factory parts" vary slightly. What you suggest could certainly be done but with the tools at my disposal I would have to cut a carb in half to properly locate the two factory holes. Unfortunatly I do not have a bunch of 48IDAs to sacrifice.
Fairly easy to locate the third hole at 12 and as I stated in the post below I do not think that the holes have to be exactly at the same Location.
Let me hear your thoughts.

[Bill Cuthbertso]

Originally Posted by Jac Mac

Has anyone ever considered simply joining the 1st & second holes to form a slot similar to a Holley & then extend that slot up toward the choke/venturi rather than drilling a 3rd/4th hole?

We are talking about adding a hole that is .039 of an inch in diameter. I think a slot would result in fuel overload and be alot harder to repair if it didn't work.

[dlampe]

I sent you a PM weeks ago about renting the tool. I guess you are not open to that.

I have 2 carbs that have a threaded port and 2 carbs that are plugged and I don't know if they are threaded behind the plug or not. Any ideas?

[Gaz64]

Originally Posted by Bill Cuthbertso

I really think that there is no really correct position for the third hole. I think that the upper area is a convenient place to put the hole because there is alot of room.
If you turn carburetor upsike down and watch the butterflies open, you will see that the progression holes are not opened in sequence. All three are open to the vacume at the same time so I do not think it matters to much if at all. The size of the hole certainly does matter. 12 o'clock seemed to work for me, but I think 2 o'clock will also work. I used 12 because it was easy to eyeball that location from carb to carb.
Lets hear your thoughts.

Bill,

Others will agree that all of the progression holes are exposed one at a time.

Originally Posted by dlampe

I sent you a PM weeks ago about renting the tool. I guess you are not open to that.

I have 2 carbs that have a threaded port and 2 carbs that are plugged and I don't know if they are threaded behind the plug or not. Any ideas?

I'd say a plugged progression port would have no threads, cheaper to make.