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Fri Feb 24, 2017 9:56 am

Hey guys, wanted to share some information for the sake of posterity. I took vacuum readings from the vacuum advance port on these carbs. Here is a picture, thought it would be useful to fellow tinkerers. Did two tries.

-Frank

Fri Feb 24, 2017 11:53 am

Thanks for sharing. I got about 15", too.

Sat Feb 25, 2017 8:06 am

Frank Bassman wrote: Hey guys, wanted to share some information for the sake of posterity. I took vacuum readings from the vacuum advance port on these carbs. Here is a picture, thought it would be useful to fellow tinkerers. Did two tries.

-Frank

Is this at idle, or at a certain RPM? I would be very interested to see the advance graphed out every couple hundred RPM to see how the advance signal compares to stock carbs, and even other sets of duals. I know on my kadrons and my current 34PICT3 I don't get a reading until you start to open the throttle, uncovering the advance drillings in the throttle body.

Sat Feb 25, 2017 11:58 am

Hey Lindwendil, this is measured at approx 3000 rpm or slightly higher, about a fourth to a third throttle, engine unloaded.

While loaded the rpm would probably start at about 1300. I do not have a tach on there but may put one for the test. We'll see.

As far as I know 034 needs abiut 200 to 250 mm hg for full vac advance. Anyone have an exact figure?

-Frank

Sat Feb 25, 2017 12:18 pm

Frank Bassman wrote: Hey Lindwendil, this is measured at approx 3000 rpm or slightly higher, about a fourth to a third throttle, engine unloaded.

While loaded the rpm would probably start at about 1300. I do not have a tach on there but may put one for the test. We'll see.

As far as I know 034 needs abiut 200 to 250 mm hg for full vac advance. Anyone have an exact figure?

-Frank
You can always mount one in the engine compartment, like I did. Makes tuning real easy when you work on your car by yourself.

:D 8)

Sun Feb 26, 2017 3:48 am

Frank Bassman wrote: Hey Lindwendil, this is measured at approx 3000 rpm or slightly higher, about a fourth to a third throttle, engine unloaded.

While loaded the rpm would probably start at about 1300. I do not have a tach on there but may put one for the test. We'll see.

As far as I know 034 needs abiut 200 to 250 mm hg for full vac advance. Anyone have an exact figure?

-Frank

Vac canisters vary, but it's easy to check with your gauge, a T-fitting, just sucking on it. I did whole bunch, and the labelled each can with the "Hg it needed. IIRC, the range was about 9 to 15" Hg on different cans.

Sun Feb 26, 2017 3:13 pm

Thanks for sharing all this helpful information!

I'm in the process of removing the stock L-Jetronic fuel injection from my 1974 914's 1.8 liter engine and putting it all it a box that will go with the car when I sell it eventually. 25 years ago I built this engine with FAT Performance's hydraulic lifter / stock grind Web Cam kit and it worked great until recently when I could no longer keep the FI system operating because replacement parts have dried up. I purchased the CB Performance 34-PDSIT carb kit, 28 mm venturis and 145 main jets and just finished wiring up the new fuel pump so I'm just about ready to put gas back in the tank and start dialing the carbs in.

I had a pair of 36 hp VW oil bath air cleaners set up for crankcase vent hose and they fit the carbs perfectly and I really like the factory look. The "T" to split the crankcase vent tube is a part from a 1999 to 2006 Audi/VW crankcase vent and has the VW/Audi logo so it looks like it belongs there. It's crazy to see a simple little Type-4 engine in there with all that wiring and hoses from the L-Jetronic system removed. Now it almost looks industrial!

I've really enjoyed reading this thread and getting the 4-1-1 on what it will take to dial these carbs in. I've got Webers and Kadron carbs on other cars so I'm kind of looking forward to futzing with this tinker-toy. I'm most enthused about the electric chokes and fabricated a wiring harness to retain the stock 914 relay board and added the electric choke wires to the existing engine wiring that connects to it.

Thanks!

Sun Feb 26, 2017 6:35 pm

Darryl, I really like those dual oil baths, I am feverishly trying to find a set of two as well for my motor, I really do not like the air cleaners that are on there... I prefer the stock look, plus the VW cleaners have a "built in" velocity stack in them.

I wanted to let you know that as of now I am running a 150 main jet in these carbs and a 55 idle with the 28 mm vents...(1699 type 1 motor) I had an annoying midrange transition with them before I did... I didn't want my mileage to drop but as it turns out It didn't the driving did get much better. I get a flat 30 mpg highway with these carbs, impressed the hell out of me!

-Frank

Mon Feb 27, 2017 12:02 am

Thanks for the update and compliment Frank! I'm sure there's going to be some jetting experiments required but just to get the car moving under its own power will be nice since it's been sitting for almost a year since it last died.

Obviously a 1.8 liter with a stock grind cam and hydraulic lifters doesn't put me in the "performance" class, I'm just wanting something that starts reliably and drives smoothly, top speed and acceleration aren't high on my list, rather the ability to be putting around in my first Porsche and returning home without needing AAA!

Thanks!

Darryl

Mon Feb 27, 2017 4:03 pm

^ I love the look of dual oil baths. I'm digging through every parts pile I come across to find a pair for an eventual dual ICT single port build.

You wouldn't happen to know the year or date code on those would you?

Mon Feb 27, 2017 7:03 pm

Lingwendil wrote: ^ I love the look of dual oil baths. I'm digging through every parts pile I come across to find a pair for an eventual dual ICT single port build.

You wouldn't happen to know the year or date code on those would you?

Yes, they are the Mann 2-clip air cleaner, 111 129 611A, used from 1954 up until around 1958.

Oil bath air cleaners are quite the little engineering marvel, to quote Bob Hoover, "a classic example of a 'two-stage' kinetic filtering element" and they remove 100% the heavier than air contaminates, especially at high speed. COOL!!!

Mon Feb 27, 2017 7:42 pm

DarrylD wrote: Lingwendil wrote: ^ I love the look of dual oil baths. I'm digging through every parts pile I come across to find a pair for an eventual dual ICT single port build.

You wouldn't happen to know the year or date code on those would you?

Yes, they are the Mann 2-clip air cleaner, 111 129 611A, used from 1954 up until around 1958.

Oil bath air cleaners are quite the little engineering marvel, to quote Bob Hoover, "a classic example of a 'two-stage' kinetic filtering element" and they remove 100% the heavier than air contaminates, especially at high speed. COOL!!!

Just be sure that they are sized properly for your application. Contrary to hopefull belief.....they do not flow as well....volume wise....as a pleated element. That being said they sre not an impediment....as long as they are sized properly for internal volume....something that the factory did quite well with.

One on each carb of that size should be really nice.

If they are too small they are restrictive and will use excessive oil, putting it through enhine...and may not filter effectively. If thetly are grossly too large they will not filter properly as the internal velocity that makes the directional change that makes the heavier particles drop out over the oil pool.....will not be high enough at lower rpms. Ray

Tue Feb 28, 2017 6:39 am

Oil bath filters are great! I however was not super happy with my results: with a FK-65 cam on a 1745, with Kads, i still had enough reversion at low rpm to create an oily mist around them, in the beetle engine compartment.

When I went to less cam ,and the CB 34 PDSITs, I also dropped the oli-baths. Maybe I should try again--

Tue Feb 28, 2017 11:32 am

I'm curious to see how the Solex 34-PDSIT carburetors behave with the more restrictive oil bath air cleaners on them. I say "more restrictive" than the cheap K&N style ones that come with the kit. The original L-Jetronic airbox had a 42 mm opening at the end of the "snout" and each of the oil bath cleaners have a 36 mm opening at the top of the tapered internal "velocity stack" so I did the basic math:

To determine that there's a 46% larger "eye of the needle" the air has to pass through. Both intakes are tapered to create a venturi effect, which I suspect is an attempt to reduce intake air temperature and eek out just a little more horsepower. Again, my goal here isn't to set a salt flat land speed record but simply provide a reliable alternative to my unreliable, obsolete FI system.

I've been babying this engine for 25 years, I rarely rev my 914 past 4500 RPM so if there is a theoretical limit to how much air can flow through the oil bath cleaners it will probably never be reached. I also think the backup air filtering feature of the oil bath filters, the kerosene soaked "coir" (coconut husks) are still more effective than the K&N style filters provided with the kit so if the oil bath isn't effective at idle, I'm still safe. I also never go off the pavement so I'm more worried about cottonwood seeds than dust!

So really, it's more for aesthetics than engineering... creating the "illusion" of that anal-retentive German engineering that draws us to these old mechanical tinker-toys in the first place! :)

Tue Feb 28, 2017 2:35 pm

^ proof that the idea isn't that crazy.

For a reasonably sized engine they are a great idea, and since you are increasing potential airflow with the dual carbs, but still limited by dual single throat carbs, it all works. I wouldn't want to do it on a big 2L+ engine, but most people know that that isn't the place for ICT's anyway :)

Too bad the throat on Kadrons is as big as it is, I'd love to do a set when my kads come back, but since I'm putting together a 1600SP soon, ICT's and oil baths is the goal.

Tue Feb 28, 2017 3:23 pm

Oil-bath filters offer intake silence. That was my interest. They also filter really well...

My thinking was if you can get 40 horses through 1, you should be able to get 80 Hp through 2, maybe more...

1300 x 4500= 5'850'000

1745 x 5500/2=4'798'750

Not an all-out race car, so I can tolerate some intake restriction for silence..

Tue Feb 28, 2017 3:24 pm

some perhaps useful perhaps not data I saw yesterday. F-ing aussies use the word carby instead of carb, don't shoot the messenger

what is interesting is the jets are set up differently left and right. I presume this is to help with reversion, depletion of the atomized fuel from one cylinder firing right before the other for the same barrel? Maybe not, but I thought it odd

I know when you are setting up linkage on a type 3, the look, listen, do it better book says to make the left carb your master and sync the right carb to it

32-34 PDSIT - 2 Left Carby
32-34 PDSIT - 3 Right Carby

Venturi - Left & Right 24mm dia

Other info:
Main Jet -
Left Carby X130
Right Carby X127.5

Air Correction Jet -
Left Carby 155
Right Carby 120

Pilot Jet with cut off valve -
Both left & right 50

Float needle valve -
Both left & right 1.2mm dia

Float Weight -
Both left & right 7.3 grams

Pump Capacity -
Both left & right 0.35 - 0.55 cc/stroke

Information sourced from my Australian Publication - Gregory's No.47 VW Type 3 1500-1600 Service & Repair Manual..

Tue Feb 28, 2017 3:34 pm

IIRC, Left and right carbs started to differ when emissions became more stringent. I'll look it up in Without Guesswork tomorrow.

Tue Feb 28, 2017 3:40 pm

As far as I recall the two carbs were jetted different due to differences in intake restriction from side to side of the factory type 3 air cleaner...............or so I read somewhere. If that is the case it does not apply to type 1 based motors with identical cleaners....

-Frank

Wed Mar 01, 2017 1:16 am

It starts with the T engines from 8 June 1966. Main jet and emulsion differ.

T engines from first June 1970 are back to having symmetrical jetting. I'ts quite the opposite of what I had thought. Sorry.

My Without Guesswork stops in 1973, not sure about later models. Interestingly, the type 4 1700s are mostly all symmetrically jetted, too.