Weber 45's?????

[dino8925]

Sorry to re-awaken a sleeper but I have a set of dual webers on my '67 Porsche 912 and the aluminum tag reads "Weber 45" and the venturis measure 36. There is only the idle mixture screws(2) and some brass vacuum tubes(2) near the mix screws with a nut machined into the metal tubes. No air bypass screws with lock nuts. The closest picture on the net I can find is calling them dual 36 idf's. Either way, I can't seem to figure out how to synchronize the front and rear throats with each other on either side. The rear-most throats (for cylinders 4 and 2) are user friendly when using the unisyn but if I put that tool on the 1 and 3, it will kill it quick. I can lean the number 4 completely out and with no popping or anything but the 1 and 3 will react accordingly. I have sprayed the carbs down and found no vacuum leaks while running. Timing won't idle well at 3 degrees before TDC. Is currently at approx. 30 degrees before. Will check compression tomorrow but confident is carb related. Any advice is appreciated. DiNo

[Jaems]

The 45's with 36 venturis are tooo big for the 912 engine. You want 40 idf's with 32 venturis or 40 Solexis with 32 venturis. Also valve adjustment is very critical to carb adjustments always do this before adjusting carbs. With 30 degrees BTDC, you are lucky if you have not burned up your engine. It should be 30-35 degrees at 3100 rpm.

[dino8925]

Cool, by too big, if I put the 86mm big bore kit on it would that make it worthy? And the main jets are only 110's. My brother adjusted the valves but did it the short way by turning the crank to TDC for the #1 and adjusting those valves as well as the closed valve on the opposite side of the engine and then vice versa. I am not a short cut guy but he's a believer so I let him try it. It seems to be running better than it did. And the timing, do you think the distributor could be 180 out? or maybe something more serious? Thanks!!

[Jaems]

A big bore kit will work just fine with the 40's. The 45's are just too big for this engine. If you want to build the engine for racing and not the street. Then the 45's might be OK. Being a 180 degrees out will not make any difference to the timing. #1 on the distributor still has to be connected to #1 cylinder.

This is a 912 engine and not a type 4 or type 1 VW type?

It maybe that you have a wrong distributor for you engine. With 45's that might be that the PO might have been doing something like they do on a VW which is not a 912 engine or even close.

You should have one of these type Bosh Distributors. type 1 or type2 031, a 022, or a RS00012. These three types are optimized for the 912 engines.

a 009 was for a VW and does not work well on a stock 912 engine. It is used for racing where the rpms stay in the upper range all the time. The older 050 replacement were OK and will get you by. However, the newer ones are nothing but garbage.

[dino8925]

O.K. got the Weber 40's with the 32mm venturis. The main jets are 110 and the idle jets are 50's. Dipped the two of them and cleaned out the jets accordingly. I also noticed the float needle valves have a ring around them but cannot catch the ring with my fingernail. I called the redline folks and was told the float level should be at 14mm so I set it then found a schematic that shows the float level at 10mm. So I already had it all together and figured I'd tune it as best I could and set the timing at a sweet 10-15 BTDC. It idles at about 900-1000. Installed new plugs and wires. Still has a slight flat spot during the transition in first gear but wasn't like the horror it was before. And even though it isn't perfect, it does have a pretty strong go about it. I'm thinking reset the floats and change those needle valves but still not sure about the dominant throats on the carbs. How to equalize and synchronize all four. The Non-dominant throats idle mixture screws can be set all the way turned in with no effect on the idle. Any Ideas? Thanks!

[dino8925]

Oh yeah, it has a "flame thrower" pointless distributor.

[WFBowen]

Can you adjust your Unisyn to work on the 2 problem cylinders without choking them down or killing the motor? Over the years, I've never had much luck with Unisyns on downdraft carbs and there are cheaper, better products out there. The Unisyn (IIRC) was really intended for the sidedraft SU's used mostly on the older British stuff.
Try this method for a basic setting. Get your motor fully warmed and idling at around 1000rpm - the revs aren't as critical as the fact that the idle is steady with no "climbing". Put a small piece of hose (like rubber fuel line) in your ear and put the other end into the top of each carb throat. Compare the sound you hear ( i.e. front to rear on each carb.) Then compare "low sound" on left carb to the same throat on the right carb and adjust to match. If you're adjusting one of the vertical rods, make sure you remember where you started (#of turns left/or right.) A smooth idle is nice to have, but the critical things are: 1.that the carbs open at the exact same moment with no delay in the accel. pump injectors; 2. that they are synced (left to right) at around 3000rpm and 3. Your idle mixture is on the slightly rich side to help in the transition to midrange running.
As for adjusting the front to rear throats, the air bypass is used at the factory for that purpose. You might get some advice about the old procedure of putting an end wrench on each side of the throttle shaft and bending the shaft to adjust the actual throttle butterflies - your decision, but remember that you'll be going down a very slippery one-way street.
Good luck & if possible post some close-ups of the sides of the carbs.

[Jaems]

I think it is PMC that makes new Weber's. They can help you with the correct air, jets etc. To get the correct adjustments for your area, (mountains, sea level).

If the Webers are adjusted correctly with the correct air, jets, and etc. There will be no flat spots . I have had to adjust my Webers only once in the last 5-6 years. That was because they change the gas in my area to 10% alcohol and I lost my idle down to about 300rpms. I prefer a little higher idle than the factory around 1000 rpms.

I am not familiar with a "flame thrower" distributor. The ones stated earlier are the only ones that I would recommend for the 912. You also need to check your timing at 3100rpms. It should be between 30-35 degrees. The distributor you have may not have the correct curve for you engine.

If you have not done a valve adjustment. You could be just whistling in the wind.

[dino8925]

Can anyone tell me what these are? My main jets are 110. Not sure what to call the others because I can't find a schematic showing the same spot where I pull these from (all from the top of the carb) but here are the numbers: 50/200/F11/ and 7OF7. Never-mind the wire holding onto the throttle linkage. If you look at the first photo closely you can see the 32 stamped into the venturi. The main throat is 36mm. There is only the fuel pump, mixture screws, and some vacuum tubes on the outside and the choke on the other which is not blanked off. Oddly there is the "45" stamped on the tin by the pump and the "36 idf 66 5L" stamped into the base. I am a little confused yet eager to find the service instructions so that I might start from scratch somehow. I do appreciate the help so far and any further help you guys can provide.

DiNo
"67 912

[WFBowen]

Dino:
As far as I can find out, those are an early IDF carb which was used on VW/Porsche aftermarket Weber kits years ago and were also factory carbs on the Alfa (type 33?)
As far as the 45 metal tag, my guess is that it's the accelerator pump jet size installed.
Once you get them properly setup, these carbs should work well on a stock 4cyl Porsche or ;umped-up VW dual port motor.
No one (myself incl.) ever likes to do this, but have you done a compression test on that motor? I think it would be a good starting point if the motor isn't responding to fine-tuning.
Bill.

[Jaems]

Also if you have not done this or have been told. You need to disconnect the linkage from the carbs while adjusting them. Then adjust the linkage to the carbs afterwards.

[djdsc]

I would pass on messing with these Weber's. They are a bit too far off the path for 912 fitment. Remember that the more normal 40 IDF Weber's come in 3 varieties each with their own special issues when installing on a 912 (perhaps 4 if you count the new EMPI units) and can be hard enough to get setup and tuned correctly.

I am not Weber bashing in fact I am a Weber guy and successfully run the early cam style pump jets units on my 912. I am wiling to take on any 40 IDF problem but I would pass on these unless you have unlimited time to research and tune them.

[dino8925]

WFBowen-Right, I am finding also that they were installed on some alpha's and I took the carbs down as far as I could and found the pump jets were stamped 4,5. Not sure if that's the same but shouldn't cause too much trouble? I did the compression test and the 1,2,3,4 cylinders were at 158,155,150,and 150 respectively so I am confident there.

Jaems-Got it, linkage disconnected while tuning.

djdsc-I am beginning to agree with you. I feel though I am in too deep now to let them go. I think I am at my wits end now as I have taken them down as far as a screw driver and soft plyers can take them and dipped them for about a half hour each and made a trip to the import place and got a couple gasket kits with new float needles and o-rings. I will attempt to fine tune once again on the morrow and if the flat spot remains, I will most likely sell for an updated set.

Thanks guys!!


DiNo
'67 912

[dino8925]

Just took a closer look at ALL FOUR idle jets to find I have 3 "50" size and one "55". I had just attempted to tune the mixture after a good clean and blow to find I could completely turn in the mixture on the right carb (cyl 1 and 2 ) and it would not effect the idle. I pulled the jets and they were clean. Carb orifaces were clean. I noticed the left side carbs were responding somewhat so I pulled the jets and found the dominant of the two throats was the "55". I want to go to "55" on the rest. Without bombarding me with the math......Does this not make sense?

[dino8925]

Oh yeah, I soaked the exterior with carb cleaner to find no leaks. I sprayed the left carb down the throat and it wanted to die. I sprayed the right side (1 and 2) and almost no response. Could the jets effect this also??

[WFBowen]

Dino:
What happens on 1&2 when, at idle, you pull each plug wire?

[dino8925]

I did try pulling the wires individually in the beginning and it did still affect the idle however slight with the non-dominant cylinders (which were 2 and 4 at first) and would die when I pulled one of the dominant (was #1 cyl at the time). (Am now figuring out the most dominant cyl had the "55" idle jet. I am going to get those jets in the morning and if I can keep it running I will test the firing if it is still non-responsive to the mixture. Thanks for the advice.

[djdsc]

I appreciate your tenacity with these and wish you all the success, but........ in order for Weber's or any carbs to be setup correctly for that matter, there are many variables that need to be correctly addressed and correctly matched. Truly, carb tuning is way more art than science. All of the following need to be addressed with Weber 40 IDF's for correct drivability on an 912/356: idle jets, main jets, air corrector jets, emulsion tubes, pump jets, exhaust jets (on the early style), secondary ventures (chokes) and the often over looked accelerator pump jet volume and duration. All this is above basic tuning and balancing technique.

There exists a known base line for the above when using the 40 IDF carbs on 912's. With the units you are attempting to use do you have any of the baseline information to work from? By the time you figure out, if ever and if it is even possible, the correct combinations with these you could have sold these and bought a pair of 40's and be well on the way to a great running car. These carbs are an unknown fitment for the 912 and may never be correct no matter how much time and money you spend on them. The internals of the carbs, passages, emulsion/mixture chambers, progression ports and on and on simply may not be a fit for the 912. Diagnosing a cars drivability by throwing money at it is seldom the best fix.

[C. Clark]

Well said djdsc,
I've always thought of engine tuning as Zen.....I like your part about art and science, although with the proper perspective and patience they can merge as one.
Webers are problematic at best, they were never really intended for the use they were adapted to. The late Harry Pellow I believe had much to do with the direction the market took, mainly because of the limited expertise available at the time.....but if one could find it..... it was financially a diminishing return, or so it seemed for rebuilding or better stated re-manufacturing....Webers were a cheaper, easier, quicker fix......the typical American way.......or so it seemed.......I had my Solex 40's re-manufactured for the 356 by Harry Bieker and never looked back........my 912 runs Weber 40's, with patience and persistence it ultimately ran and runs well today.........44's, 45's whatever........ are just wrong for the 356/912 engine........sorry.
Chas.
356912911

[mpetry]

My 912 runs great with 40IDF-70 Webers, big bore kit, and recurved 031 distributor.

Jetting: 125 mains, 190 air correction, F7 tube, 32mm venturi, 55 idles.

I would concur with DJD above that these webers are not worth messing around with. They are probably the ones from Ebay seller "alfa1750" and are not really meant for our cars. You'll never get the accelerator pump working right.

One other hint- if the mixture screws are turned out 3-4 turns, go up a step on the idle jets. In order to get the transition set right (off idle to about 2500 rpm) the idle screws should only be turned out 1 to 1 1/2 turns.