Stock 34PICT-3?

[BTL069]

Cobey,
Let us know how'd you go with that carb modification once you're done.

Volkenstein,
Thanks for your generosity. My bug is a 1500 SP. I'm in the process of upgrading it to a 1641 DP with a 34 PICT carb.

[conradk]

Hi,

I'm back again after letting the beetle sit for 6 or more months in disgust. So, it turns out that the problem is that none of the replacement carbs I got had the proper vacuum connection. That's explains many things.

Do I just drill a 1-1.5mm hole in the plug? I don't have a press, or way to align the hole, is it critical? How far am I going in? And then I have to find a brass fitting. Anyone have a good source for one?

Thanks,
Conrad

[volkenstein]

Conrad,
          I think a 1.5mm hole all the way through wouldn't pick up enough of a vacuum signal from the venturi. I measured the hole and it's about 2mm at the venturi, and then stepped down to 1.5mm further along.

Drilling. Get a 2mm bit and drill as straight as you can in the centre of the boss all the way through. Next, get a 4mm bit (or nearest imperial size), wrap a piece of tape 10mm up from the tip and drill into the boss until the tape depth. You could get a 1.2mm welding tip, cut the end off & file flat (.5mm thick?), drill it to 1.5 and file like mad till it's 4mm in diameter. Wedge this in the boss then whack a 4mm tube on.

Have a think about it. It's nice to have a sacrificial lamb to try on :lol:


Enjoy
Volkenstein

[conradk]

I scrounged around and found the "original" carb that was on the bug when I bought it. So, the source of my confusion was that the original carb didn't have a vacuum feed tube, but had the hole. My bug had an 009 on it and ran like crap, so that's another mystery solved. Had I known that mechanic #2 put the engine in (which is a nice engine, and cost more than what I bought the entire car for) I wouldn't have sought him out to fix the carb problem. Oh well.



I checked around and I didn't have metric size drill bits, I went with the smallest I could find which was a 1/16". I checked it against the original and it was larger than the original hole. Guessing that the hole may taper larger towards the venturi, and given that's an extremely small bit, I decided to go for it.

I took the vacuum retard tube off the old carb to use on the new vacuum port.

Now, my intent was to pull the carb and work on it on the bench, but I couldn't find my handy carb wrench and wasn't about to spend two hours pulling and installing the carb without it. So, I grabbed my fire extinguisher, shop vac and drill and headed out to the rear of the bug.

The Bocar has an indentation where the vacuum hole would normally be. I'm guessing that's on purpose, because it is centered and made my job super easy. I first drilled out the hole incremently larger making sure I didn't go further than the existing plug. The new tube just barely fit in the opening, so I knew that's what I wanted and moved on to the vacuum hole itself.

I then drilled out the vacuum hole slowly with the 1/16" bit. I stopped frequently to vacuum out the hole. I eventually popped the bit into the Venturi - hopefully not putting bits of metal into the carb, but probably did. It is soft metal if that makes me feel any better. I put the shop vac hose on the top of the carb and let it suck away just in case I would lucky enough to suck out any incidental debris.

I gently whacked in the new vacuum tube until it was in as far as the original.

I plugged the vacuum retard nipple and moved the vacuum feed hose over to the new outlet.

Started the car up and kept shifting into gears cuz I couldn't believe how smooth it was. I did do a minor adjustment to speed up the shift transition, which is amazing in and of itself. And I still have a small crunch going into reverse if I go too fast, but that's small potatoes now that I can cruise around in all forward gears.

Thanks for your help!!!!

[conradk]

Here's the new carb in action.



My camera battery died right afterwards, which didn't matter as I was about jump in and drive around the neighborhood. :-D

By the way, you will see an extra vacuum port lower down on the manifold neck. A previous mechanic thought my problem was a leaking vacuum port on the manifold, so I gave him an auto T3 manifold and he welded in the larger vacuum port. (That is positioned behind the T3 port.) I'm not sure why he kept the T3 port there instead of welding it up. He was a bit of a sloppy mechanic. Nice enough but sloppy. Anyways, his welding works. Someday I'll pull that manifold off and touch it up so it looks pretty.