To all 34 Pict 3 carb experts

[cyberdyne systems]

Ok so I run the standard carb and distributor and air cleaner, I've got the same set up in my bug. I can set up the bug carb ok and it runs well. I set up the bus one (rebuilt solex with no shaft play), but on the initial settings of 2.5 turn out on the mixture screw I get a pulsing where it slows and revs. Once i have opened the mixture up quite a bit more I find a much smoother running and can lower the revs back down with the bypass screw. Is this fine or do i have a problem as i can't set it near the initial settings? I checked the plugs and they are a great colour with no soot. Oh one last thing I just rebuilt the distributor as a spring came off the advance weights as the retaining bit was broken, fitted new points and the dwell measures just right.

The reason i'm asking is I have had a hesitation when accelerating or under load up a hill say. Like a misfire. I have cleaned out the tank and fitted a new screen filter in there, I have a paper type filter in line under the tank, plus the late model fuel pump has a screen too. Now this was before I rebuilt the distributor which may have caused/contributed to the hesitation. But still I can't set up the carb at the 2.5 turns.

Two things that may effect it are the carb to manifold joint doesn't seem flat (without the gasket in place) so its the gasket thats making a seal (but if I was gettting a leak here, how come spraying it makes no difference and I can set it up albeit with more mixture). Also there are no cooling flaps or themostat, so this could mean taking longer to warm up the manifold once the choke is off, and there definately is an improvement when its been run for longer (I don't see icing but the manifold is cool to touch). I cleaned out the heatrisers too - though with an aftermarked 4 - 1 header (drilled heatrisers) only one side gets hot as the design doesn't pull through like a stock exhaust, and the air cleaner has the warm air feed working).

Just wondered what opinions are on this?

 

[Trikky2]

The pict carbs for beetle (1302 S - 1303) 1600 twin ports had a slightly larger main jet and idle jet than the same carb fitted as stock to the type 2.

Back in the old days we used to cure poor running and flat spots on T2's by changing the jets to beetle ones. (basically 1 size up)

Theres a good chance that this might explain the symptoms you describe so it may be worth checking to see what you have. (The idle jet, being external, can be checked without any dismantling).

As for the heat riser - theres not much you can do about it with a 4 into 1 exhaust manifold but it is certain that having a thermostat and flaps fitted to the fanshroud has a significant effect on the warm up and correct running of the engine. The colder the ambient temperature the more noticeable the effect is. VW fitted them for good reason.

In cool temperatures, running around town for instance, you would be surprised at how long the flaps stay closed. The other thing that so many seem to ignore/forget is that the thermostatat is not an on/off switch and in cool weather the vehicle will often run for prolonged periods with the flaps partially open - maintaining the engine resonably close to optimum temperature.

 

[cyberdyne systems]

Thanks Trikky2, makes sense what you've said. I'll take a look at the idle/pilot jet to see if its size differs to a beetle one i have. I'm also in agreement over the flaps and thermostat, should never be removed and i'll source the bits so i can reinstate and then see how it feels.

 

[cyberdyne systems]

Ok here's what i've found:

Pilot: 55
Main: 125
Air: 80

I've tried to find what a type 2 version's jets would be, and from what I can find the main is correct, pilot might be ok though some say 57 and air should be 75 or 80 for gear (& bus maybe?).

So I think I have the option to increase both the pilot and main perhaps. I have to say the colour of the plugs and the general feel at mid revs and above suggests the main and air are probably ok, but i could gain some slight performance (up to a T1 version carb).

Does anyone know the definative jetting for a type 2 34 pict 3? I've read thats its to do with the aircleaner being different to a type 1 and the extra weight of the vehicle and possibly fuel emission/economy?

 

[cyberdyne systems]

Update:

I had chance to look at everything again, i had wanted to check the valve gaps when cold too just to be sure. Well after trying two different carbs and jets etc, I felt so sure there must be some sort of leak somewhere as it just refused to run smoothly with the mixture around 2.5 turns until i took it quite far out.

I tried to pull at the servo pipe, i'd not really considered this as the van never stalled and the servo was working well making me think i didnt have a leak from the pipe, but as I moved it the revs changed. I had to try it a couple of times to be sure and realised there was a split in the pipe that meant that the servo was still able to work when the pipe was stationary but i was having to rich up the mixture at idle to get it to work. Now having trimmed the pipe back a tad (i'll get some new as its quite old), I found I could set the carb from the base setting of 2.5 turns and get the idle nice and constant at that level. I've gone back to the original jets and will see how it runs from here!

 

[lard]

Update:

I had chance to look at everything again, i had wanted to check the valve gaps when cold too just to be sure. Well after trying two different carbs and jets etc, I felt so sure there must be some sort of leak somewhere as it just refused to run smoothly with the mixture around 2.5 turns until i took it quite far out.

I tried to pull at the servo pipe, i'd not really considered this as the van never stalled and the servo was working well making me think i didnt have a leak from the pipe, but as I moved it the revs changed. I had to try it a couple of times to be sure and realised there was a split in the pipe that meant that the servo was still able to work when the pipe was stationary but i was having to rich up the mixture at idle to get it to work. Now having trimmed the pipe back a tad (i'll get some new as its quite old), I found I could set the carb from the base setting of 2.5 turns and get the idle nice and constant at that level. I've gone back to the original jets and will see how it runs from here!

nice one

When I read your post it did sound like the same issue I had - two different carbs (origanol and new one) and both wouldn't adjust on the standard settings, had to make it much richer, all down to a vacuum leak but couldn't find it (new flanges, checked boots, pipes e.t.c.)

My issue was likely a leak from the manifold boot, I've got it in the garage and still can't see any holes in it! - at least you managed to track it down exactly by the sounds of it, with mine I replaced the boot as that was all it could be after changing out most of the other bits (along with the fuel pump rod being upside down) and the issue has gone, always nice when you can put your finger on the problem and know it's gone for good!

 

[cyberdyne systems]

always nice when you can put your finger on the problem and know it's gone for good!

until next time... :lol: