I have a 28 pict on my 1300cc, will it make any improvment running a 31 or 34 pict carb instead?
Will a 34 pict carb bolt on to the exsisting single port manifold?

no the 34 wll not bolt up. and id be surprised if the 31 did as well.
you would probably have to change the manifold. its not a hard job but if i was doing it id stay away from the 34 pict its a pig of a carby. others will disagree with me on this i know but its the only one that came from factory with a flat spot. i removed mine and went back to the 31 and a 32/36 webber progressive later.

if your going to that much effort you may want to look in to twin carbs

VW wouldn't have sold them if they had flat spots from new.

34pict3 are a smooth as butter carb if you know how to work with them, they just have alot of little idiosyncrasies being more complex then early carbs and lots of wear after 40 years can make them piggy.

Main problem is most of the 1600 population has been fitted with 009 distributors and they do not work well with no vac advance and worn throttle bushings causing air leaks also makes for crap running.


One of the worst problems that I've found nearly all 34pict3 carbs suffering from though is the overtightened idle jet syndrome.

It peens over the seat and once that's done they wont idle well unless you back the jet out a turn or so but then it wants fall out.

My choice carb on 1600 twinports though is the 31pict3 from 70s 1300s.
It took me a while to getting the jetting right with that auxillary power jet to stop mid stumbles but after that it had great power right through and consistantly got 8.5-9L/100 around town.

You can buy adpaters to fit bigger or smaller carbs on the different manifold.

You could fit a 1500 30pict carb but the gains would be minimal, a 1300 is never gonna be a power house, just enjoy the fuel economy it gives.

joel, there is an article form 1972 in the volkswagen magazine that talks about this problem, it also mentions one of the big race drivers that was driving them refused to use them for this reason.
ive seen them have this problem new in both the solexs and brosals. so im not making things up. also the old man was a vw mechanic at a dealership so if anyone should know how to set one up it would be him, but even he hates them.

I didn't say you were making shit up but you are making a mountain out of a molehill.
If they did flatspot when the cars were new it was enough that most people didn't notice.
All of my supers and a couple of my standards have had 34pict3s when I bought them and none of them had flat spot issues except my white 71 S bug, but only cos it had a 009, once fitted with a SVDA it was smooth as any single port.

As I said you just need to know how to work on them, the owner of the garage I worked at was the boss of the dealership service department here and knew them inside out, he taught me alot about them.
I've got a box full of old dealership service bulletins from when I worked there, the only drama VW Australia had was when S bugs were first released they fitted double vacuum dissys to them and they were recalled and fitted with single vacuum as the DVDA gave a flatspot, terrible mileage and performance, oh and the dashpots they fitted to 76 beetles I think it was used to gum up and hold the throttle open.

They are world wide the most common vw carb, millions of VWs use them, the new brazillian and mexi repoops are useless paper weights but can still be made to work without flat spotting.
I actually thought it was strange someone that hates 34pict3s but likes progressives, if ever there was a useless carb its those weber progressives.



Anyway none of this is answering the OPs questions.
Long and short of it you're really not going to gain much other than making it thirstier by fitting a bigger stock carb.
You could fit twins but that will only bring the performance up level with a bog stock 1600.

I'm experimenting at the moment with how a 34pict3 will run on a 1300 S/P but the 34 has been modified for a 1600 formula vee; I picked it up second hand.

It has larger jets etc.. and no choke butterfly and gizmos; hopefully there will be more power over the stock 30pict1; becasue of the larger carb but also larger manifold size.

I don't anticipate a large flat spot if any; because the butterfly has been welded to close the hole; but also a 1600 Vee always runs with a 009 and like my car will be driven flat-out all the time; for street purposes this set-up would be rubbish! But this is going a "race" car.

Cheers

Shaun

Ok, so who has advice on what sized jet I should be using on my 1500TP with a 34 PICT 3 (replacement) carb?

I get a massive flat spot on acceleration when the engine is cold. In fact it's less of a flat spot and more of a near stall. My mechanic said that if I fiddle around with the jets I should be able to eliminate it. It has a 125 at the moment. Bigger? Smaller?

I'm running a VA distributor by the way.

I'm thinking bigger.