Carb Upgrade - from Single to Duals

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BusBassist
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Carb Upgrade - from Single to Duals

Post by BusBassist » Thu Jul 18, 2019 9:55 am

I have a 1973 bus with a type 4 - 1.7 engine from a 1970 914 Porsche. It came with a Weber center mount carb which, is not performing well and it’s time to switch to duals.

I am running an electric fuel pump that is mounted near the transmission nose cone, out and away from the engine bay.

I’m not sure of the distributor type but it can be seen here:



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I have recently acquired two sets of Solex 32-34 PDSIT- 3 carbs. I am seeking input to determine if I have complete sets, and if not, what am I missing?

Both sets came from the classifieds from the Samba. This first one came off a 1973 parts bus:

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This second set came from a running 1974 bus and looks to be in better shape and more complete:

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Once I determine if I have all of the components, how do I evaluate the health and work-ability of the parts? (I have read and studied Colin's treatise on setting dual's and know it's a complicated operation.)


Thanks for your help and input.

Jeff
Late 73 Bay w/a transplanted 914 Engine.

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satchmo
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Re: Carb Upgrade - from Single to Duals

Post by satchmo » Thu Jul 18, 2019 12:49 pm

Well, you are in for a treat.

Just to answer your main question, the second set up is more complete, with the central idle spider tubing, balance pipe and the correct intake air filter box (although the lid is on with left and right reversed - EDIT: no it isn't). It is nice to have two sets of carbs so you have easy access to spare parts.

I would recommend you get the carbs cleaned and rebuilt, then follow Colin's dual carb procedure.

The distributor looks okay. It is a dual vacuum/dual advance unit, which is what you want.

Your fuel pump needs to be fairly low pressure or it will overwhelm the float needle valve in the carb bowls. I think it's like 3-4 psi, but I don't recall exactly since I no longer have a 73 bus.

Have you been through this thread?

viewtopic.php?f=3&t=13619

Good luck!

Satchmo
By three methods we may learn wisdom:
First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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BusBassist
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Re: Carb Upgrade - from Single to Duals

Post by BusBassist » Thu Jul 18, 2019 9:21 pm

Thanks for the reply Satchmo. And thanks for the link to Xyzzy’s post on the same topic.

Ironically, I’ve been dealing with a similar hesitation issue with my fuel delivery system - hence my desire to ditch my center mount progressive carb.

Where does one send carbs to be rebuilt these days?

Thanks,

Jeff
Late 73 Bay w/a transplanted 914 Engine.

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satchmo
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Re: Carb Upgrade - from Single to Duals

Post by satchmo » Thu Jul 18, 2019 11:40 pm

BusBassist wrote:
Thu Jul 18, 2019 9:21 pm


Where does one send carbs to be rebuilt these days?

https://www.volkzbitz.com/
By three methods we may learn wisdom:
First, by reflection, which is noblest;
second, by immitation, which is easiest;
and third, by experience, which is bitterest. -Confucius

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SlowLane
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Re: Carb Upgrade - from Single to Duals

Post by SlowLane » Sat Jul 20, 2019 11:31 am

satchmo wrote:
Thu Jul 18, 2019 12:49 pm
The distributor looks okay. It is a dual vacuum/dual advance unit, which is what you want.
Just a caveat here: not all air-cooled VW vacuum advance/retard cans are the same. And '73/'74 dual-carb buses are quite the odd ones out.

Many air-cooled VWs had vacuum advance/retard cans (commonly referred to as DVDA nowadays for some reason), and the excellent Old Volks Home Ignition page is very useful in deciphering the characteristics of different ones.

If you peruse the list, you will note that most of the advance/retard cans have pretty much the same characteristics for the retard side: generally 11-13 degrees of retard. But the '73 & '74 manual trans dual-carb engines have a retard range of 16-18 degrees.

This can mess up your ignition timing when following the procedure of setting the timing at the prescribed setting (10 degrees ATDC with hoses on) if you don't have the correct vacuum can that provides 16-18 degrees of retard. If the can you have is from some other vehicle, or is the generic DVDA sold by all the vendors, and only provides 11-13 degrees of retard, then you will be setting the timing 5 degrees too retarded and beating your head against the wall wondering why you have so little power.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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BusBassist
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Re: Carb Upgrade - from Single to Duals

Post by BusBassist » Sun Jul 21, 2019 2:04 pm

If you peruse the list, you will note that most of the advance/retard cans have pretty much the same characteristics for the retard side: generally 11-13 degrees of retard. But the '73 & '74 manual trans dual-carb engines have a retard range of 16-18 degrees.

This can mess up your ignition timing when following the procedure of setting the timing at the prescribed setting (10 degrees ATDC with hoses on) if you don't have the correct vacuum can that provides 16-18 degrees of retard. If the can you have is from some other vehicle, or is the generic DVDA sold by all the vendors, and only provides 11-13 degrees of retard, then you will be setting the timing 5 degrees too retarded and beating your head against the wall wondering why you have so little power.
Thanks SlowLane -

I have been concerned that my distributor may not be correct. Especially since this engine is a Frankenstein: as stated above, the engine is from a 1970 914 and the fan shroud has a serial number from 1978.

It may be that the dizzy is original to the bus and that when the engine was switched out, they kept it. BUT - who knows? I’m going to check the numbers on the distributor against the info on the link you sent.

And - how do I evaluate the vacuum values on the can?

Thanks,
Jeff
Late 73 Bay w/a transplanted 914 Engine.

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SlowLane
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Re: Carb Upgrade - from Single to Duals

Post by SlowLane » Sun Jul 21, 2019 4:15 pm

BusBassist wrote:
Sun Jul 21, 2019 2:04 pm
how do I evaluate the vacuum values on the can
I fear that the extent of my knowledge on this subject is limited to what I've already presented: simply that the '73/'74 dual-carbed manual transmission buses had that extra bit of retardation.

Now, if you compare the idle timing on all of those cars with a vacuum retard on them, you should see that the base timing (ie, with vacuum hoses off, so no advance or retard taking place) works out to about 7.5 degrees BTDC. So even if you can't deduce the type of can that you have from the numbers stamped into it, you could measure the amount of retard you get by timing your engine to 7.5 BTDC with hoses off (or even time it statically. Muir had a good description on how to do that.), then connect the hoses and see how much the timing retards from your base. If it goes to 10 degrees ATDC, then you have the right can. If it only goes to 5 degrees ATDC, then the can is from another engine.

All this is assuming that the retard side of your can functions at all. They are notorious for failing and introducing a nice big vacuum leak to confuddle you.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Amskeptic
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Re: Carb Upgrade - from Single to Duals

Post by Amskeptic » Sun Jul 21, 2019 8:47 pm

SlowLane wrote:
Sat Jul 20, 2019 11:31 am

This can mess up your ignition timing when following the procedure of setting the timing at the prescribed setting (10 degrees ATDC with hoses on) if you don't have the correct vacuum can that provides 16-18 degrees of retard. If the can you have is from some other vehicle, or is the generic DVDA sold by all the vendors, and only provides 11-13 degrees of retard, then you will be setting the timing 5 degrees too retarded and beating your head against the wall wondering why you have so little power.

We set our timing at 28* @ 3,400 rpm all hoses off, so it won't affect road performance. The only difference between the 10*ATDC and the 5*ATDC cans would be a lower idle with the 10* and a slightly faster idle with the 5*. This is easily compensated for at the central idling circuit ... most times.

Hey Jeff, your photograph of the '73 carb set has the air filter box mounted backwards. The air intake is supposed to be in front of the right carb.
ColinInSaltLakeCity
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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BusBassist
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Re: Carb Upgrade - from Single to Duals

Post by BusBassist » Sun Jul 21, 2019 10:10 pm

Hey Jeff, your photograph of the '73 carb set has the air filter box mounted backwards. The air intake is supposed to be in front of the right carb.
ColinInSaltLakeCity
Thanks Colin. I pulled these parts out of the shipping box and set them up in the back of my bus for the photo shoot. Having never laid eyes on an actual set of original duals, I was guessing at best as to how they are organized.

Please send my greetings to my home town. I tried to contact Rallybug last fall when I was there but was not able to connect - next time.

I think a dual carb set up is on tap for the 2020 lap for both myself and Judahthedog when you come to Rochester.

JC
Late 73 Bay w/a transplanted 914 Engine.

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Amskeptic
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Re: Carb Upgrade - from Single to Duals

Post by Amskeptic » Mon Jul 22, 2019 7:17 am

BusBassist wrote:
Sun Jul 21, 2019 10:10 pm

I think a dual carb set up is on tap for the 2020 lap for both myself and Judahthedog when you come to Rochester.

JC
Oh hail yes .... :flower:
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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xyzzy
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Re: Carb Upgrade - from Single to Duals

Post by xyzzy » Mon Jul 22, 2019 9:35 am

Your distributor should be a 205J, and alternatively a 205N will work as well.

In addition to what Satchmo mentioned it also appears:

1) You have the metal collars and rubber grommets on the idle jet solenoids -- DONT LOSE THESE. Take them off before sending to Volkzbitz for rebuild.

2) The vacuum can appears to be correct -- verify it works.

3) The air cleaner box in the last picture looks best. You're missing (in the photos) the rubber donut piece of the warm air intake valve which should mount to an opening on the firewall which connects to the warm-air-intake duct mounted to the reverse side of the firewall.

Donut piece:
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Inside-firewall warm air intake duct
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4) It looks like there's whats left of a part number on one of the carbs, it should end in a "Q" for the 73.

Send the carbs to Volkbitz for a rebuild.
---
1973 Westfalia
Encinitas, California USA

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BusBassist
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Re: Carb Upgrade - from Single to Duals

Post by BusBassist » Mon Jul 22, 2019 10:31 am

Your distributor should be a 205J, and alternatively a 205N will work as well.
I was able to retrieve the numbers stamped on my distributor:

2031 173 005
021 905 205E

I’m thinking this one will work fine for my situation.


Xyzzy - Per the missing rubber donut piece, I do have both the mount on the inside of the fire wall as well as the duct on the backside as shown in your photo. I have to imagine that rubber donut piece may be difficult to source.

Colin, I have one more set of duals on the way (from Robbie) so Judahthedog and I will put together two good sets and patiently await your arrival for the 2020 lap.

Thanks for all of input from all of you. This is a great community of faceless friends.

JC
Late 73 Bay w/a transplanted 914 Engine.

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xyzzy
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Re: Carb Upgrade - from Single to Duals

Post by xyzzy » Tue Jul 23, 2019 12:39 pm

The 205E is for a 72 Manual Transmission Type 2. It's not correct, you should try and find a 205J or 205N, and make sure your vacuum can is correct.

If your 205E is off a 1972 Type 2 MT then Vacuum canister is 021905271B/1 237 121 it should produce 8-12° @ 200mm Hg Advance and 11-15° @ 170mm Hg retard.

A correct 205J with vacuum canister 021905271E/1 237 121 should produce 7-12° @ 180mm Hg Advance and 16-18° @ 210mm Hg retard.

In my opinion, if you're going to do this, you should really do it right and get a 205J or 205N with a NOS or validated vacuum canister . The 205E with that vacuum can is advancing 8-12 degrees @ 200mm Hg instead of 7-12 degrees at 180mm Hg and 170mm retard as opposed to 210mm Hg.....
---
1973 Westfalia
Encinitas, California USA

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BusBassist
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Re: Carb Upgrade - from Single to Duals

Post by BusBassist » Tue Jul 23, 2019 8:01 pm

Thanks Xyzzy,

I very much appreciate your help and guidance on this. I probably won’t install these carbs until Colin’s 2020 lap next summer so this my learning/prepping/parts gathering time.

JC
Late 73 Bay w/a transplanted 914 Engine.

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asiab3
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Re: Carb Upgrade - from Single to Duals

Post by asiab3 » Tue Jul 23, 2019 9:06 pm

Where is this vacuum line going? As far as I know, no progressive carb has ever been improved by the addition of vacuum retard.
Screen Shot 2019-07-23 at 10.59.52 PM.png
Screen Shot 2019-07-23 at 10.59.52 PM.png (1.54 MiB) Viewed 7646 times

Did you know there are at least four different parts for needle-type idle cutoff solenoids? I didn't either until I realized I had driven three times around the distance earth's equator without a spare 30pict3 solenoid. Xyzzy gave me two NOS spares this year and I lucked out last week when I had to swap it! Colin, I would like to donate one to Chloe when you have a steady mailing address. Xyzzy, can you post the PDSIT solenoid part numbers for our collective edumafication?

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Carb delivery is on hiatus. When I showed up, the good soul was cussing like a sailor at the new Progressive. He kept the Solexes for now, but will ship if he has an epiphany. My apologies.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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