34Pict Tuning Problems

[hosspowerinc]

I cant seem to figure my carb out. I have a fresh bone stock 1600dp with a 205 dvda and bocar 34 Pict 3. Only the advance side of the can is hooked up on the distributor and the timing is 30 degrees. Fuel pressure is 2.5 psi at all rpm. I have a 55 idle, 70 air, 127.5 main, 47 power. I have good idle and off idle performance as well as full throttle performance but at about 30-40% throttle at low rpms it just falls on its face, especially when it gets under load in 3rd gear.

This is in a ghia and the air should be an 80 but I dont think that is what is causing my problem. I swapped everything to another carb body I have and it acts exactly the same. Timing is smooth and spot on and the vacuum advance works fine (I have a digital timing light). The accelerator pump works fine and there is no hesitation when flooring it. It seems to be going lean to me but with the engine stock I dont see why the jetting should be any different.

One interesting thing is it seems to be more rpm dependent since you can give it the same 30-40% throttle at high rpm in a low gear and it acts fine. I stuck a 60 idle in it with no change. I dont have any different airs or mains to try but Im not sure either would fix it. Im not sure on the exact float level but the float itself was pretty much level. Thanks for any help.

[vugbug68]

I've never had good luck tuning that carb even with the correct vacuum distributor and thoroughly cleaning the carb. Usually I can't get it to idle and if I do there is hesitation right off idle.
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71 super

[kombiboy]

The 34 carb can be a hassle, but I've had good luck when I've followed these steps exactly as they're written.

http://www.vw-resource.com/34pict3.html

[borninabus]

it's your distributor.
30deg all in is not enough advance.
DVDAs are a lazy, crappy unit and you should set it to 35-38 all in with just advance the hose connected.

there are better options out there.

here is the *OFFICIAL* 34PICT thread if you missed it.
http://www.thesamba.com/vw/forum/viewtopic.php?t=56411&highlight=idle+adjust

karmann's also came with a bigger main (130) to accompany the bigger air jet.
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[mharney]

In order to get it to idle at the correct speed, how far open is your big screw?

[spencerfvee]

hi are you setting your timing with the vacuum hose on ? if you are take the vacuum hose off and set the timming at 32degs total with the motor running about 2,800 rpms then put the vacuum hose back on . rejet your carb with a 130 main jet those carbs are jetted way lean . then check the acc pump jet to make sure the pump jet is discharging the fuel between the butter fly plate as it opens . the pump jet should give a good shot of fuel right into the intake manifold . this is over looked a lot .a other thing allways run a stock air cleanner it has a built in 6 "stack that helps to keep fuel stand off in check . if you dont run a stack with a air cleanner the fuel wants to climb out the top of the carb just my two cents spencerfvee...........................................................................................................................................

[hosspowerinc]

[modok]

The old school way to go about it is to TRY stuff, go richer and leaner, try more advance and less. See what fixes it. Once you know what is actually going on then you can go about fixing it properly

[Altema]

[hosspowerinc]

[hosspowerinc]

Im also having a heck of a time trying to find an 80 air. Anyone know where I can get one?

[baked beetle]

spencerfvee is bang on with his suggestion.
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[spencerfvee]

hi . not true on useing stock jets on a stock motor .to make my point . i worked at a vw dealer in 1973 on all 34 pic carbs. we installed 130 main jets . these carbs were running so lean . they would not pull small hills with out down shifting they were dogs . and why do you want to go to a 80 air jet . that is going to lean out the carb out even more . all so the distributor you are useing is not the best . i like useing a 1968 to 1969 auto stick distributor it has a faster adv. built in . the distributor you have has a longer adv. your intl. setting TDC . your distributor the only thing your vac. adv. does is pull the adv. from TDC to 8 degs intl. were the auto stick setting is 8 degs intl. it makes a big differnts on how a motor runs . spencerfvee

[hosspowerinc]

Thank you spencer. Just the info I was looking for. My timing is at 8 degrees initial to get the 30 total so maybe I have the better unit. At any rate Ill get a bigger main jet, leave the air alone and report back.

[mharney]

Stock jets were for GASOLINE. Now we have ethanol in it, and things are different.

The float level is important. It should be 17-19mm from the top of the carb body to the fuel level when it is full. Lots of times I find cores that have thick washers under the needle and seat, and that causes the fuel level to be too low. Something to check.

80 air will not necessarily lean out the carb. It will encourage more fuel earlier in transition which may help.

As far as idle jets, I use around a 50 for the pilot, and 55-60 for the idle jet, and that tends to do well. Depending on your intake heat, you can do better than that sometimes. Realize that the two jets for idle circuit work in parallel, together, and when the two sizes are relatively close to each other, the increase of one jet is not that significant, like it is with single idle jet carbs.

[hosspowerinc]

[mharney]

Naw.. the auxiliary jet supplies fuel to the circuit that the large screw contributes air from. Its there to linearize the response of adjusting the big air screw, so that it does not lean significantly as you increase the air flow by opening the big screw, or richen by closing it down. It is part of the low speed "circuit". That's why there are two air bleeds above the bore. One is for the idle jet, and one is for the auxiliary jet.

[spencerfvee]

hi . i work with these 34 carbs a lot . and i have found out over the years that . when rebuilding them . you will find out that . no matter what you do to some 34 pic carbs . they just wont work right and i end up junking them . and who knows what kind of life they have had lol seeing that you have tryed a other 34 pic carb. on your motor and the motor ran the same . i would try changeing the distributor next . to a 009 or a vac. distributor . allso when testing allways make sure you know a carb or distributor is in good working cond. so your test wont be a waist of time . i have found out that the stock 34 pic carb on a stock motor with stock jetting does not like anthing bigger than a 70 air jet vws spot on . with the 70 air jet .with a stock 127 main jet . the only time a bigger air jet works on a 1600cc motor is when i have used a 132 main then i make and use a 110 air jet and these motors have a header and mild cam in them . to point out how well a 34 carb can work on a bigger motor i have a 2,180 cc motor with a 34 pic carb that has had the ventrui opened up to a 30mm it runs just like a stock vw would till you pass some one on the free way . and if i dont watch my speed i will be doing 85mph and 90mph like right now lol a 34 pic carb is not a bad carb once you get it dialed in just my two cents. take it or leave it good luck spencerfvee...............................

[Altema]

[mharney]

Jack, any that you are going to do that with send to me!