Upright Engine / Type I Carburetors!

[Bookwus]

Hiya All,

I went out to Bill Trafton's and sorted through all his junk carburetors. Practically none are complete having been picked over pretty good. But with some patient sorting I was able to construct two 30PICT3s. One for a manual and one for an AutoStick (both my VWs use a 30PICT3). Bill charged me about $10 for each carb.

I brought 'em home and pulled the AS carb apart to rebuild it (never have rebuilt an automotive carburetor). Got it done today and strapped it into the AutoStick Bug. Cranked it over and it runs like a dream! Yeehaw! And I haven't even dialed the thing in yet. This is so cool. A practically brand new Solex for $25.

[Manfred]

Awesome. I have no idea what a auto stick are or a auto carburetor is. Can you explain?

[Bookwus]

Hiya Manfred,

Awesome. I have no idea what a auto stick are or a auto carburetor is. Can you explain?

I will give it a shot................

Telling the difference between a carburetor designed for a manual application and an AutoStick application is fairly easy if you remember that AutoSticks were never equipped with throttle positioners. I'll show how that affects carburetor design in the pictures below. Bear in mind though, that this is not the only difference between the two versions of the (basically) same carburetor.

A 30PICT3 manual carburetor...........



And a 30PICT3 AutoStick carburetor............



Starting in 1970 all manual carburetors were equipped to work with a throttle positioner. The manual carb has an extra arm and ball joint (red arrow) whereas the AutoStick does not. Notice the spacer on the throttle shaft (just below the red arrow) in the AutoStick picture. That takes the place of the throttle positioner arm in the manuals carb.

The yellow arrows point to the boss on the rear of the carburetor where you will find a vacuum port in the AutoStick carburetor. This vacuum port controls the shift action initiated by the control valve in an AutoStick. It is not usually found in replacement carburetors. Consequently there are many AutoStick drivers who are experiencing harsh and abrupt shifting because they lack this port on their replacement carbs.

The blue arrow points to a vacuum port in the manual carb, but there is no such port in an AutoStick carburetor. That's because this port supplies vacuum to the throttle positioner which was not installed on an AutoStick.

The green arrow designates the vacuum port that feeds the retard signal to a DVDA type distributor. In this case why the AutoStick carb has a port and the manual does not is a bit of a mystery to me. Consider that neither of these carburetors were designed to run with a DVDA. Further, in my experience with 30PICT3s I have seen these vacuum ports on manual carbs and not on AutoStick carbs. There seems to be no discernible pattern to the presence or absence of these particular vacuum ports.

[Amskeptic]

I will give it a shot................

Some of the confusion with vacuum ports relates to the fact that two different styles of throttle positioners were utilized, and that the air filter preheater switched to vacuum-actuated in 1972, and the distributor retard started in 1971 as well.

Two piece throttle positioners were introduced in 1970, they stuck right out of the carb in 1969.

Any "pict3" carb has an air-bypass idle speed control (big brass screw).
Any "pict2" carb sets idle speed directly at throttle lever.
Colin

[Bookwus]

Hiya CK,

......Some of the confusion with vacuum ports relates to the fact that two different styles of throttle positioners were utilized, and that the air filter preheater switched to vacuum-actuated in 1972, and the distributor retard started in 1971 as well.

I'm with you on that. The problem for me in figuring out that pesky retard vacuum port (why it's there on some and not on others) is that the 30PICT3 was designed to sit on top pf a single port and it went the way of the dinosaur with the introduction of the dual ports in 71.

Why even have that (green arrow) port if a DVDA was never even going to be hooked up to a 30PICT3? Or might that port have been intended for something else? Or is this just a case of running into a bunch of carburetors that have been hacked by capricious POs?

[Amskeptic]

Hiya CK,

......Some of the confusion with vacuum ports relates to the fact that two different styles of throttle positioners were utilized, and that the air filter preheater switched to vacuum-actuated in 1972, and the distributor retard started in 1971 as well.

I'm with you on that. The problem for me in figuring out that pesky retard vacuum port (why it's there on some and not on others) is that the 30PICT3 was designed to sit on top pf a single port and it went the way of the dinosaur with the introduction of the dual ports in 71.

Why even have that (green arrow) port if a DVDA was never even going to be hooked up to a 30PICT3? Or might that port have been intended for something else? Or is this just a case of running into a bunch of carburetors that have been hacked by capricious POs?

If you are dealing with later carbs, they try to make universal applicability.
OEM-at-the-time carbs I think were trying to address a couple of different markets not to mention different models.
Colin