Mark: Very informative post. I'd appreciate your comment on one little-discussed possibility for off-idle hesitation. On page 10 of the Fuel System chapter in the Orange Bentley, step 9 in the procedure for adjusting a 34PICT-3 has one adjust the volume control screw to give maximum rpm and then to turn it clockwise until the rpm drops by 20 - 30.
I seem to recall reading that this final adjustment is to promote smooth acceleration off idle. Have you any evidence that this is the case? Jack >So long as the SP vacuum-only distributor isn't giving >too much advance at idle (easy to check, at a normal >idle speed the timing shouldn't change when the vacuum >advance line is disconnected) it's fine on a >singleport - but the ported vacuum signal is greater >from a 34PICT-3 than it is from any of the 30PICT >carbs, so it's not a good idea to use one on a >dualport unless you're prepared to fiddle with the >return spring tension to dial it in for that >application. >The 0 231 178 009 distributor gets a lot of bad press, >blaming it and it alone for a "flat spot" on >acceleration. It's true that an SVDA or DVDA >distributor will usually alleviate the problem to some >degree (any engine will respond to more timing advance >up to a point - the problem is knowing when to stop >before it causes damage), but the root cause is lack >of sufficient intake manifold heat...and it's worse on >a dualport because the larger diameter of the intake >tract reduces flow velocity. VW acknowledged that >problem on `74 engines (dual preheat pipes) and on >`75-up Euro-spec carbureted engines (a much larger >preheat pipe, ~3/4"). I've never had a problem getting >a 34PICT-3 to run OK with an 009 provided the manifold >heat is good and the thermostatic aircleaner is >working properly - WITHOUT plugging the throttle plate >hole or richening the jetting more than one >step...tampering with the carb like this is the wrong >way to address the problem, it's all about intake >temperature and off-idle timing. > >--- [EMAIL PROTECTED] wrote: > >> Marc, >> Could you clarify your last post. The thread was >> about a problem >> with a 34-Pict-3 carb (dual port); so can I assume >> you're saying not >> to mix and match VW parts of differing applications; >> specifically the >> single port vacuum only advance distributor with a >> 34-PICT-3. Or is there >> a problem with the single port Vacuum advance >> distributor even in >> the stock application on the single port engine. In >> other words, do you >> suggest using a 009 distributor instead of a stock >> vacuum advance unit >> on a single port motor (stock configuration)? >> >> Thanks, >> Brian >> >> >> ----- Original Message ----- >> From: "marc vellat" <[EMAIL PROTECTED]> >> To: "Air-Cooled Volkswagen Discussion List" >> <[email protected]> >> Sent: Sunday, May 06, 2007 7:43 PM >> Subject: Re: [vintagvw] Carberator Problem? >> >> >> > If you have a stock DUALPORT distributor it's >> worth a >> > shot. The vacuum-ONLY type used on singleports has >> its >> > own issues - it'll most likely provide too much >> > advance, too soon, which can harm the engine...I'd >> > choose the 009 over it. >> > >> > --- Eric Larson <[EMAIL PROTECTED]> wrote: >> > >> >> Would changing the distributor really make that >> much >> >> of a difference? I'm running a 009 cent only >> >> advance. I've heard people say that the cause >> >> hesitation, and I've heard others say they are >> >> better. Maybe I'll put the stock vacuum advance >> on >> >> and see how it works. I'll double check all the > > >> typical vacuum leak areas like you said. I might >> >> have missed something. >> >> >> >> Eric >> >> ----- Original Message ----- >> >> From: Mike<mailto:[EMAIL PROTECTED]> >> >> To: Air-Cooled Volkswagen Discussion >> >> List<mailto:[email protected]> >> >> Sent: Saturday, May 05, 2007 8:27 PM >> >> Subject: Re: [vintagvw] Carberator Problem? >> >> >> >> >> >> The accel pump adjustment is to compensate for >> >> slight differences/wear in > > >> the accelerator pump itself and linkage slop >> .... >> >> If I remember from my >> >> rebuild kit and Bently manual, the spec on the >> >> pump is a certain number of >> >> CC's of fuel for a given number of "squirts" >> with >> >> the pump activated thru >> >> the throttle linkage. If you get too much total >> >> fuel, you adjust it back and >> >> vice versa. >> >> >> >> The stock main jet on the carb is a little on >> the >> >> lean side; this was part >> >> of the first attempts at exhaust emissions >> >> reduction on the engine. The >> >> stock main is a 127.5 and I replaced it with a >> >> 130....much better. >> >> >> >> Like Mark suggested, another possible cause for >> >> the stumbles is a blocked >> >> manifold heat riser or one with insufficient >> flow. >> >> If you have a stock >> >> muffler (or an aftermarket with the heat riser >> >> pigtail) make sure the end of >> >> the pigtail is centered in the exhaust outlet >> >> (remove the left tip, look >> >> into the muffler and you should see the outlet >> end >> >> of the pigtail centered >> >> in the opening....if it is cocked slightly, use >> a >> >> big screwdriver to center >> >> it... muffler exhaust flow around the end of >> the >> >> pigtail helps draw the heat >> >> riser exhaust flow. Check to make sure your >> center >> >> manifold to cylinder head >> >> riser rubber couplings are not leaking. Check >> to >> >> make sure your throttle >> >> plate bushings are not leaking air (unhook the >> >> return spring from the >> >> throttle arm and try to move it up and >> down/fore >> >> and aft....anything but the >> >> slightest hint of movement means you have worn >> >> bushings). >> >> >> >> mike >> >> 73T1 >> >> >> >> >> >> >> >> ----- Original Message ----- >> >> From: "Eric Larson" >> >> <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> >> >> To: "vintagevwlist" >> >> >> > >> ><[email protected]<mailto:[email protected]>> >> >> Sent: Saturday, May 05, 2007 11:37 >> >> Subject: [vintagvw] Carberator Problem? >> >> >> >> >> >> > What does the adjustment on the accel arm of >> a >> >> 34 Pict -3 carb supposed to >> >> > do? I assume it makes the accel pump squirt >> >> faster when you hit the >> >> > throttle? (I have the non-alternator carb >> that I >> >> modified to work.) >> >> > Problem is - hesitation. it hesitates after >> it's >> >> warmed up. The hesitation >> >> > isn't there when you rev it in neutral. Can >> you >> >> adjust that out with the >> >> > accel arm adjustments? Do I need bigger jets? >> >> > >> >> > I'm also running 33" mud tires, which I'm >> sure >> >> doesn't help things. They >> >> > really kill the power. No power off the >> start, >> >> and it hesitates when the >> >> > choke turns off. Anything below 2000 rpm is >> >> slow. Descent power till about >> >> > 3500 rpms, then slow again. Should I try >> >> different tires and see if the >> >> > flat spot disappears? Or should I adjust the >> >> carb some more? I have a set >> >> > of Kadrons. Would they help with the >> tire/power >> >> problem? Any ideas are >> >> > appreciated. >> >> > >> >> > Eric >> >> > >> _______________________________________________ >> >> > vintagvw site list >> >> > >> >> >> > >> >[email protected]<mailto:[email protected]> >> >> > >> >> >> > >> >http://lists.sjsu.edu/mailman/listinfo/vintagvw<http://lists.sjsu.edu/mailman/listinfo/vintagvw> >> >> > >> >> >> >> _______________________________________________ >> >> vintagvw site list >> >> >> >> >> > >> >[email protected]<mailto:[email protected]> >> >> >> >> >> > >> >http://lists.sjsu.edu/mailman/listinfo/vintagvw<http://lists.sjsu.edu/mailman/listinfo/vintagvw> > > >> _______________________________________________ >> >> vintagvw site list >> >> [email protected] >> >> http://lists.sjsu.edu/mailman/listinfo/vintagvw >> >> >> > >> > >> > __________________________________________________ >> > Do You Yahoo!? >> > Tired of spam? Yahoo! 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