34 pict 3 vac signal to SVSA distributer too strong at idle

[hdaiken]

The ignition timing on my '74 ghia does not change with engine rpm. It has a single hose, vacuum advance only distributor. Initially, the vac advance mechanism was stuck, but once I freed it up and started the car, now I find that the generic 34 pict 3 carb is providing full vacuum, even at idle. The vacuum to the distributor comes from the port on the left side of the carb, by the idle and volume screws. I measured up to 20 inch Hg from this port at all rpms, which is essentially manifold vacuum. As shown in the pic, the vacuum source for the port is below the throttle plate, even when the throttle is closed (throttle screw with slight clearance at the fast idle cam). I noticed that the throttle plate doesn't shut as close to horizontal as a Solex 34 pict 3 I have in the garage. Is there some way to adjust the throttle plate so it will shut closer to horizontal and put this port above the throttle plate, or is this a defect of this generic carb, or am I missing something?

Thanks for any input.

[busdaddy]

Bummer, looks like the quality control guy at Sum-Ting-Wong mfg. was off that day.

You can try loosening the screws on the shaft the hold the plate slightly and tap each side of the plate with a blunt punch to seat it in the bore better (more closed), but it could just be a result of loose tolerances. (tighten screws after).

The best solution is to ask Tim @ https://www.volkzbitz.com/ to build you the correct German carb, yeah it's way more than that budget carb, but you only have to spend once.
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!

[DesertSasquatchXploration]

Had the same problem with my $$$ (REDLINE) carb, remove the butterfly 800 grit paper brake the sharp edges and deburr the two holes reinstall the butterfly with screws lose let it find its happy place fully closed and then snug them up should be fine. You can run some 1500 grit around the carb throat too chances are a burr has boogered up the works.

(Big difference when building a car over just putting one together)

(Ill take a tight fitting carb any day over a worn out one)

[HighDesert56]

Is that a witness mark of where the throttle plate used to sit in the bore? If the plate hasn't shifted on the shaft, maybe worn throttle shaft bores/bushings?

[Alstrup]

Idle has likely been "adjusted" on the mouse stairs instead of the volume screw.
An SVA distributor does not work with a 34 Pict3.
Get the right distributor and adjust the idle correct and I´m pretty sure things will begin to work as intended.
_________________
https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[oprn]

Correct me if I am wrong here but to me that is the wrong port to connect the distributor to. That one is intended to power the retard side of a dual vacuum pot and/or perhaps the throttle position pot for high idle on deceleration on smog engines. The proper port for the distributor is about 1/2 way up the carb body above the throttle plate.

The second problem as Alstrup says is that is the wrong distributor for that carb. The Solex 30 PICT-2 if memory serves is the correct carb match with the correct vacuum signal for that distributor. That combination came on the '67 - '69 1500 SP engines.
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[hdaiken]

This is on a 1974 Ghia, engine code AH44909 (California model). The distributor is VW part number is 113 905 205 M. It's had a 34 pict 3 and that distributor all the time I've owned it (since the early 80s). So that just leaves 8 years or so unaccounted for. It's ran well with that setup- the distributor advance worked fine and it has always been connected to the port by the volume and mixing screws on the left side of the carb. Still has the metal vent tube used when connecting to that vac port with short sections of vac hose. I installed the generic 34 pict 3 because the Solex got gunked up from sitting too long. I may try to clean it and rebuild it since its vacuum sensing hole is not below the throttle plate.

Based on the above advice, I removed the throttle plate and tried to clean up any burrs on the edge of the disk. I reinstalled it and even with the throttle adjusting screw removed, the throttle plate won't close enough to cover this vacuum hole. The attached pic shows the clearance (about 3/16") between the tab on the throttle arm the adjacent linkage in this condition. With the throttle plate removed, the throttle plate shaft will rotate further- until the tab on the throttle arm touches the arm below it (clearance goes to zero). So, it seems to me that the throttle plate is slightly oversized- it hits the carb body and won't rotate enough to cover the vac hole.

I could install a non-vac Bosch 009 for $46 and call it a day, but I'm not sure I'm ready for the outcry.

[HighDesert56]

Since the carb may be junk anyhow, it may be worth taking the throttle plate back out and running it over some 400 or so sandpaper being careful to follow the opposing bevel angles. It shouldn't take too much to get it to close just over the port, then you can finish it off with something finer.
That's all assuming the bore is round and free of bumps or burrs.

[kreemoweet]

The throttle shaft has to be perfectly located for the plate to be able to close all the way. Perhaps it was assembled incorrectly, or someone's been messing with it. Suggest you undo the nuts on either side of the throttle shaft so it has some sideways play, and then see if the plate will close completely, covering the vacuum hole.
_________________
'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[Alstrup]

The distributor is definitely not the correct model for neither the car nor the engine, so at some point some imbesile has replaced the correct one.
The one you have is used on a ´68 1500 type 1 manual trans, and is SVA.
the one you SHOULD have had is a 043 905 205C (Alternatively a 113 905 205AN)
That said, if youre outside Ca and don´t have to clear the yearly visual inspection I would suggest that you instead use a 043 905 205 and set idle timing to 7,5-8 degr. btdc. Much better.

Wrt the carb. If the suggested methods for remedy fail I am sad to say that you have likely gotten a poor example of a copy carb. The butterfly position is all wrong. If the butterfly can not come down to the correct position the carb will never work as it should.
_________________
https://www.thesamba.com/vw/forum/viewtopic.php?t=435993