34 PDSIT SOLEX CB Performance

[Slow 1200]

left and right jetting differences are related to the air cleaner, yes

More discussion about that and PDSIT jetting here

[gooFI]

Does anyone know if the CB 28mm venturi will fit an original 32 PDSIT? Since I've had difficulties finding 26mm T-2 venturis.

[PumaVW79]

[FreeBug]

The 28s are just a tiny bit loose compared to the stock 26 or 24, which makes it easy to take them in and out, unlike the stock ones, which need persuading...

[gooFI]

Thank you for the information. Those 28mm venturis will be useful in my upcoming build.

[Frank Bassman]

About dual oil baths... Here is my version.

-Frank

[daos]

what a great thread! just what a carb/carby noob like me needs.

trying to get my ex FI 1600dp with 32 PDSIT 2/3s tuned in. the carbs were from an older 1500 so not particularly well suited regarding jetting.

to make matters worse i also have a 009 clone. all fitted by the PO.

has new valves & guides + upgraded exhaust with j-tubes + replacement air cleaners + electronic ignition. fitted by me.

jetting is 45 idle, 130 main, 180 air.

right now it's running unevenly - especially at idle (carbs are not synced) - and the right hand side of the engine is really cold. after a 20 min steady drive, temps (measured at exhaust close to manifold) are: #1 & #2: 70°-90°C, #3 & #4: 180°-220°C.

unsure if left side is too hot but right side is far too cold. seems to run ok under acceleration/deceleration but stumbles under constant load. and at idle #1 & #2 don't seem to do much. i can pull the plug wires with pretty much no change.

if i'm off topic here please let me know but since everything is related it's not always clear exactly where to post.

[Slow 1200]

45 idle sounds lean, also, have you checked sync?

[daos]

haven't synced yet, hunting down a sync tool. could that cause a hot/cold side?

[Frank Bassman]

Sure can. Unsynced dual carbs are worthless. You probably have 24 or 26 mm vents. Double check.

-Franm

[daos]

ok, good to know. syncing as soon as i can. also need to check again, more thoroughly, for air leaks before anything else. i fixed one, there may be more.

[FreeBug]

I gather this is a type 3 engine (because of the fuelie bit)? You say they are from a 1500, right? The only type 3 1500 which came with twin carbs was the 1500 S, which had 21.5 (very early!) but mostly 23 mm, a bit smaller than the 1600's 24mm.

[daos]

yes, it's a type 3. was looking at the spec sheets and the nearest thing judging by the jet sizing was a 1500. i'm not even sure if they're a matching pair, need to look at the numbers. but the float weights don't match - 7,3g and 7,0g. i'm pretty sure that doesn't help anything so i'll change one of those. a friend has a couple of spare 32 pdsits knocking about that i can use for parts.

will check the venturi size tomorrow when i'm in the garage, that should reveal more about their age. also ordered some new jets in a few sizes. i already changed up from 125 to 130 mains which seemed to improve things slightly. slow progress.

[daos]

checked out the venturis, they are 21,5. too small for a 1600?

also i can confirm they are not a matched pair. main jets are in different positions (if it matters). pilot jets - one has the ball, one is closed. as i mentioned before, floats are different weights. the lighter one is also flatter due to the way the main jet is located below it, so i can't just swap in another 7,3g.

will try with the new jets when they arrive and see where it goes.

[FreeBug]

[Frank Bassman]

You are going to have one hell of a time dialing those puny venturies in. My money is on you're going to end up with very tiny jets because the vacuum signal will be so strong and your engine will definitely be choked out.

I once ran a 30 pict 2 on a 1600 and jetted it 125 main 55 idle and I THINK it had a 110 air and I fouled the plugs super quick. I think I ended up with 50 idle and 110 main and it was still rich but didn't trash the plugs. (Still super dirty) It was more an experiment than anything but I learned a lot from it. 30 pict 2's have 30mm throttle plates and 24 mm vents I THINK, someone confirm. I know they are way smaller than the 34 picts or pdsits

-Frank

[daos]

yeah, it's going to be fun.. i'm certainly getting good at pulling the carbs and tearing them down and rebuilding. they are quite enjoyable to work on.

i have a spare set of pdsits i can cannibalise for 23mm vents, and a couple more on the way in, so i can put together a matching set - at least in terms of the construction.

ordered a bunch of jets from ebay, will be experimenting to see what works. any recommendations for baseline with the 23mm vents? how about 50 idle, 130 main, 160 air?

ultimately i aim to reinstate FI on this car, albeit a more modern version. but would be good to get it running halfway decently so i can use it this summer.

checked compression just be sure, have a healthy 9 Bar/135 psi on all four. good spark too so the issues are definitely fuel/timing related.

[Frank Bassman]

I'd try to source bus carbs and cannibalize them for their 26 mm venturies. Then you can jet them 137 or 140 main, 55 idle and go from there.

I think your carbs will want smaller than 130 mains but I'm not sure they make em that small try the 130's and do let us know how you get along please!


-Frank

[daos]

found this supplier on ebay with a good range of solex jets:
https://www.ebay.co.uk/usr/carb.deals?_trksid=p2057872.m2749.l2754

bus carbs would be nice. will definitely update once the jets arrive and i start experimenting. just to clarify - this car is a bona fide back from the dead vehicle, after 20 odd years languishing in the woods of northern sweden.

here's a shot from yesterday's carb workshop

[vwpieces]

Just rebuilt a 1600 Single Port
Web cam 86 grind and their cam followers
Web cam single valve springs
8.1CR
Some match porting in heads and aluminum intakes hogged out Intakes have MB on castings, no idea how or where they were from. Studs were too wide for the Solex, so some creative drilling for helicoils brought the studs closer to fit these carbs. Also running the bakelite spacers.
VW 034 SVDA with old pertronix, no vacuum at idle...
Timing @ 28* vac line disconnected/plugged. Pulls to 44* when line connected on accel.
Heater boxes and an old Ernst stock exhaust, welded on flanges and gaskets. All ports cleaned up for flow. And home made damper pipe that is larger ID and O2 bung. Made tail pipe from an old industrial engine J-Tube. Sounds good.

I have 2 sets of the PDSI carbs, both appear to be older aftermarket sets. One set has the pressed in air correction jets and had 26mm venturis. Chose NOT to use this set because of the fixed air correction jets.

Now on engine are the pair of H32/34 PDSI 2-3 actual left and right carbs.
Have the CB 28mm venturis
Some stock Brazilian car air filters with VW and 040 part number on top with K&N filters.
Current jetting to get into ball park and running decent on engine stand.
55 idle
115 air correction
160 mains
Stock rebuilt 40HP type fuel pump with 2 PSI
Float level about 12mm
Tried to follow some of the jetting others have used but this engine wasn't having it.
I am close to what this set originally had installed with 24mm venturis, 52.5 idle solenoids, 115 air correction and 155 mains.


Not sure how you guys are running 180 ish air correction jets as My engine would not even rev with 130 and higher. Ended up going down with better results.

Now my question is about throttle plate positioning and balance tube...
With balance tube crimped off and setting up with old Uni-Syn metal synchronizer I get it equal at throttle plates @ 900rpm. Choke lever arms are not bound up. Now when I un-crimp the balance tube I drop rpm to about 600ish rpm.
Seems odd and making me question things.
Should I use the timing to gain back the rpm, keeping throttle plates as set with balance tube crimped?
would drilling holes in throttle plates help here?

I have an LM2 wideband hooked up and will also use it to get it dialed in once installed in my 68 bus.

_________________
68 BUS
83 JETTA TURBO DIESEL
83 2dr JETTA 16V
81 Turbo Diesel Jabbit