| Author |
Message |
mcdonaldneal
Samba Member
Joined: June 13, 2013
Posts: 2649
Location: Gullane, Scotland
|
 Posted: Fri Jul 10, 2015 6:57 am Post subject: NOS PDSIT carbs. How to check if they are right for engine? |
 |
|
I have been having ongoing problems with the PDSIT dual carb setup in our 2000cc automatic bay window camper. I have it setup more or less ok, following advice and procedures from here on the Samba, but the idle remains variable, and there is little response from the idle circuit screws.
All discussed in a thread here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=630184&highlight=
Anyhow, I spotted and bought a pair of unused, NOS PDSIT carbs on a popular auction website.  Which are allegedly suitable for a 2 litre type 4 in a bay.
They are slightly different from my current, stock carbs. They do not have the hot idle valve, which is specific to the automatic, and the central idle circuit speed screw has a bolt head, rather than a slot.
I haven't taken it apart to check the main and air correction jet sizes, but I will do. It seems in perfect condition, still with caps and plugs on, and with a kind of clear sealant on the idle circuit 'choke' solenoid.
There are some identifying marks, including a sticker that ends in 'T3'. Could that mean it was originally destined for a type 3?
I've had a good search around, but couldn't really find useful specs, other than jet sizes in Bentley, so I'd be grateful for any comments or info anyone has, particularly:
Are they indeed suitable for my 2l bus?
What would be the effect of not having the hot idle valves, and should I transplant on the ones from my old carbs?
Thanks in advance!
_________________
1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
Stop dead photo links! Post photos to The Samba Gallery! |
|
| Back to top |
|
 |
mcdonaldneal
Samba Member
Joined: June 13, 2013
Posts: 2649
Location: Gullane, Scotland
|
| Posted: Thu Jul 16, 2015 3:43 am Post subject: |
|
|
Ok, a little more information, for those who might be interested.
The part number tags on the carbs are 071129027 (left) and 071129028C (right). I presume that means it's some sort of generic replacement carb, suitable for more than one model?
Googling the part numbers brings up a German spares website, and suggests they are suitable for a 2000cc bus (LKW).
The main jets, air correction jets and idle cutoff jets are different from my original carbs, and a different combo than any of the Bentley specs for '72-'74
I'll put the comparisons below, but I think I will end up bolting them on, and seeing how they go! Hopefully the lack of a hot idle valve won't be a problem? Might be a while before I have time, but I'll update when I do. Any other 'expert' observations are welcome! 
Original carbs (2000cc Auto)
Main jet x135
Air corr 160
Idle cutoff pilot jet 52.5
NOS carbs (no auto hot idle valve)
Main x132.5
AC 140
Idle 55
1974 (all below from Bentley)
Main x130
AC 175
Idle 52.5
1973 auto
Main x132.5
AC 155
Idle 50
1973 Manual
Main x130
AC 140
Idle 55
1972
Main x137.5
AC 155
Idle 55
_________________
1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
Stop dead photo links! Post photos to The Samba Gallery!
Last edited by mcdonaldneal on Fri Jul 17, 2015 3:52 am; edited 1 time in total |
|
| Back to top |
|
|
Xevin 
Samba Member
Joined: January 08, 2014
Posts: 7635
|
| Posted: Thu Jul 16, 2015 10:29 am Post subject: |
|
|
This may be of no help. Pretty sure early 80s (80-82?) UK spec Vanagons used solex PDSITs on some models. There is a YouTube vid of an English fellow? Tuning a 1980 Solex PDSIT dual set up which would mean Vanagon. In some parts of the world Vanagons are known as type 3. You being in Scotland. Perhaps you might find info looking up Vanagon Carb set ups. Hope I didn't send you on a wild goose chase. Cheers.
Maybe these guys could help you with the specs.
http://www.coolairvw.co.uk/Information/547/VW_T3_or_Type_25_Model_Identification.html
Link
_________________
Keep on Busin'
| 67rustavenger wrote: |
| GFY's Xevin and VW_Jimbo! |
| Clatter wrote: |
| Damn that Xevin... |
| skills@eurocarsplus wrote: |
I respect Xevin and he's a turd  |
| SGKent wrote: |
My God! Xevin and I 100% agree  |
|
|
| Back to top |
|
|
918griffin
Samba Member
Joined: February 08, 2013
Posts: 39
Location: Glendale AZ
|
| Posted: Thu Jul 16, 2015 10:50 am Post subject: |
|
|
| Those carbs look great! I have a set on my 2.0 and so far so good. |
|
| Back to top |
|
|
SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
|
| Posted: Thu Jul 16, 2015 12:50 pm Post subject: |
|
|
| Quote: |
Original carbs (2000cc Auto)
Main jet x135
Air corr 160
Idle cutoff pilot jet ???
NOS carbs (no auto hot idle valve)
Main x132.5
AC 140
Idle 55 |
Assuming same size venturi, The NOS mains are one stage leaner but the air are 4 stages richer. 3 AC =~ 1 main so they are richer at the top end and about the same at the low end if I remember my jetting correctly. The slope favors richness on the top end on the new carbs. The idle will determine how far in or out the mixture screw works best. It has been 35 years since I jetted a carb for performance but I think that is how it works.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
|
| Back to top |
|
|
mcdonaldneal
Samba Member
Joined: June 13, 2013
Posts: 2649
Location: Gullane, Scotland
|
|
| Back to top |
|
|
mcdonaldneal
Samba Member
Joined: June 13, 2013
Posts: 2649
Location: Gullane, Scotland
|
| Posted: Fri Jul 17, 2015 3:51 am Post subject: |
|
|
I had a small window yesterday to start fitting the new carbs.
Started on the left. Got the old one out without too much bother. Swapped over the linkage bracket and the rubber gasket for the air horn. Shiny shiny!
Took out the idle circuit screws, which are beautiful compared to the gnawed up old ones! Put a dab of glycerine for lubrication on the o rings and reinstalled. A drop of engine oil on the choke and throttle plate pivots and bolted the carb in. The choke plate was wide open cold, so I loosened the retaining ring to adjust it, but it was too stuck to move. With the ring off, it popped off easily enough, but the choke internals are fancier than the old ones. I figured that the arm on the carb should fit between the wires on the choke, so a bit of fiddling and it was back together! Next up, the right side!
_________________
1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
Stop dead photo links! Post photos to The Samba Gallery! |
|
| Back to top |
|
|
mcdonaldneal
Samba Member
Joined: June 13, 2013
Posts: 2649
Location: Gullane, Scotland
|
|
| Back to top |
|
|
mcdonaldneal
Samba Member
Joined: June 13, 2013
Posts: 2649
Location: Gullane, Scotland
|
| Posted: Fri Jul 17, 2015 6:30 am Post subject: |
|
|
So, I've been back out to the farmers shed and fitted the right hand carb.
Two issues; there seems to be a vacuum port on the new carb which is capped off. I've left it capped, but I wonder what it is for? Any ideas?
Second, when I fitted the carb the long linkage bar between the carbs wouldn't fit in, but I just adjusted the mounts a little and all was good.
Struggled to get the bus started, because my chassis battery is on its last legs, but the split charge arrangement I have allows me to link in the leisure battery, which was enough to get started.
What a difference!  
Idles smoothly, hot and cold, very nice power delivery and the idle circuit adjustment screws are working again for the first time in over a year!
I haven't adjusted anything away from how they came out of the box, apart from the chokes, but they are both fully open when the engine warmed up.
Fine tuning still to be done, but I'm very happy so far!
_________________
1978 marino yellow Bay Dormobile camper
1969 signal orange Karmann Ghia convertible
1976 martini olive Bay Dormobile camper
Stop dead photo links! Post photos to The Samba Gallery! |
|
| Back to top |
|
|
SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
|
| Posted: Fri Jul 17, 2015 8:39 am Post subject: |
|
|
to know what that vacuum might be for, put a vacuum gauge on it and see when that idle comes in. If it is present at idle then it goes to below the throttle plate. If it is present only when the throttle is opened then it is ported vacuum and drove a device like the distributor vac can, canister purge valve, vac egr etc.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
|
| Back to top |
|
|
|
