Weber 40IDF Carbs

[ron69912t]

Looks like i am going to have to replace the Solex 40PII-4 carbs on my 69 912 so I can pass the state emmissions test.

Where is the best place to buy a weber 40IDF conversion kit?

I found prices range from $600 to $960 for a conversion kit...yikes!


Thanks,
Ron D

[Steve F]

Here Ya Go!

http://www.cbperformance.com/

[craign]

try

www.piercemanifolds.com

they are a little cheaper than others but absolute experts on the Webers

Craig

[C. Clark]

I bought mine from CB Performance, they get bashed here from time to time but they work for me, fast service and the best price.
Good luck,
Chas.

[ron69912t]

Thanks for the leads. CB has the best price and they are in stock. Another supplier said they were in short supply and back ordered.

What required changes will I run into with the gas lines and linkage? The Maestro says to cut the banjo ends off the stock gas lines but I don't want to do that. Is there another way? Run all rubber gas lines with a "T" connection?

How about the stock fuel pump does it put out enough pressure for the Webers or will I have to change it?

Does anyone have the instructions for installing the Weber 40IDF kit so I could read it ahead of time just in case.

Thanks for all your help.

Ron D

[C. Clark]

Ron,
Use the search here and you will pull up lots of info on Webers., tuning and such. As for my install, I replaced the old fuel pump with a Facet electric, I made my own block off plate out of 3/16 aluminum stock, very easy, and added a fuel regulator, I personally believe the regulator is the trick to having a trouble free installation. CB has the regulator and JC Whitney was the cheapest for the Facet pump, yes JC Whitney. As for the fuel lines, I modified the old ones and added the rubber line that is in the kit, the installation came out very clean. Oh yea, a fuel filter would be a good idea, old Porsches are known for rust in the tank. I've been running the Webers since Sept. and so far everything has been good with the new carbs.
Good luck and I hope this helps,
Chas.

[Efrain68912]

I have the Weber 40s and use the stock fuel pump, no problem.

[Green 912]

Random thoughts. Pellow is right, it IS OK to cut the stock fuel lines. Use a pipe cutter so the cut is nice and clean with no burrs that might dig into the rubber lines and it doesn’t make little metal flakes that get into things. The pipes will line up well. Check and retighten the band clamps after driving sum as the rubber tubing has a way of “relaxing” some after installation. The conversion plates work very well but if you want a somewhat cleaner looking install PMO makes a nice set of intakes.

Spend much time adjusting the arms so that both carbs open at the same time, move at the same rate and open fully. I measure the butterfly openings as the carbs open at 25% 50% and 75% open making sure that both not only start opening at the same time but move at the same rate. Remove the ventures while adjusting; it makes it easer to see what you are doing. All you are measuring for is that both are the same at any given time. I pull the carbs open by the lever arm in the back of the motor, not pushing down on one of the linkage arms. Pushing on the arms makes things slightly uneven. I like to fine tune lincage length by pushing down slightly on the top of each lincage arm. Pushing on the “short” arm (the one that is laging opening it’s carb) will make the motor run better at the point when the butterflies start to open as this evens things out a little. Likewise pushing on the “long” arm will make it worse by opening it’s carb even earlier. Keep going back and forth and adjusting one side until both have the same effect.

The stock pump works well for stock motors using Webbers and is well within the pressure and flow rate needed by them. Personally, I always use a fuel filter and install it prior to the pump. Webbers have little screens in them but the Webber supplied screens can let some big enough stuff past and into the carbs workings to wreck all kinds of havoc. With really rusty tanks with bad tank socks (which is many of them) the Webber screens will also slowly clog up and lean out the motor at speed and do so unevenly. You then start adjusting the carbs trying to correct something that keeps changing.
The rear inside carb nuts can be a bear to get to, you can make a tool by cutting the correct size box wrench short and grinding it thin on the sides and the arm. I use blue locktight to keep things snug but still be able to get them apart. Make sure that all the intake sealing surfaces are clean and smooth. Air leaks suck. Cut all the gaskets so that they don’t block any intake airflow at all. I like the PMO thick gaskets as they help isolate the intake heat from the carbs. Don’t polish the insides of the intakes; they are supposed to be a little rough. Smooth surfaces will help the fuel to cling to the intake rather than staying atomized and going into the motor when it is supposed to.

Jetting... The following is just an opinion! A good place to start for a stock 1600CC 912. 28MM ventures, 115 mains, 200 air correction, F11 emulsion tubes and 50 idle jets. If you have an “improved” motor (cam 1720CC ect) try 32MM ventures, 130 mains, 180 air correction, F7 emulsion tubes and 55 idle jets. All motors seem to be a little different and this is just a recommended place to start.

[ron69912t]

When I ordered my Webers today the folks at CB told me the Weber 40IDF's need 3 to 3-1/2 psi fuel pressure (3-1/2 psi max.) and the stock fuel pump would work on a stock 69 912.

But I read that many of you have changed to an electric pump for more pressure. I assume you all have modified engines or know something else.

What is the correct recommendation for a stock conversion? How much psi does the original mechanical fuel pump put out?

Thanks,

Ron D

[craign]

Ron,

I am running a stock fuel pump with Weber 40's on my 69 with no problems.

To be honest I don't know what the fuel pressure output is......

Craig

[Efrain68912]

Ron, I know of many very hot 1720s with a stock fuel pump that work perfectly fine. I've got a 1720 myself with the stock fuel pump, it works fine. Don't make the conversion more difficult than it needs to be. I also run the fuel filter after the pump.

[ron69912t]

Here is what my 912 Shop Manual says for a stock 69 912 fuel pump.

Pump Pressure: 2.9 to 3.5 psi at 1,000 to 3,000 rpm with float needle valve closed.

Minimum Fuel Delivery: 7.9 U.S. gallons per hour or 16.9 US fluid ounces per minute at 4,500 rpm.

Stoddard catalog states you can vary the stock pump spacer gasket thickness (P/N 616.108.441.00) to alter the psi. They say Solex 40PII-4's require 1.9 to 2.6 psi.

CB told me Weber 40IDF's need 3 to 3-1/2 psi (3-1/2psi max).

FYI
Ron D

[wwwcad]

Hi Efrain,

You run the filter after the fuel pump? What's the advantage? I wouldn't think it could make any difference in overall pressure, but could introduce more particulate into the fuel pump, no?

Bill

[Efrain68912]

A friend of mine recently breathed on my motor, and that's where he put it. I suppose if you were worried that your tank was full of junk then you'd want to run it before, but mine is pretty clean so I'm not worried about it. Its just a cleaner installation. Actually, I used to be pretty paranoid about it, so I ran two - one before and one after. However, it was pointed out to me that it might cause a lean condition at high rpm. With the filter before the fuel pump, it might cause a slightly lean condition at high rpm, I suppose.

[HarryD]

In my work, I design things to move all kinds of gritty, dirty, and/or corrosive things from one place to another. I always put my filters after the pump. Most fuel pumps are of the positive displacement type and can move a pretty big piece of junk without harm.

If you put the filter before the pump, when (not if) the filter clogs, you starve the pump and risk damage to the diaphragm because the pump will cavitate. In severe cases, the pump will literally self destruct.

If you want to protect the pump, put a Screen or strainer in front of the pump to catch the big chunks.

[wwwcad]

Hi,
Good point. It also occurred to me that there's a screen in the fuel pump as well, no? I haven't gotten around to rebuilding that yet, I'm still working on the crankcase. I guess the key is also cleaning up the gas tank in the first place. I'm going to use the Por-15 gas tank kit which recoats the interior of the tank and eliminates the rust. Should go a long way to reducing the particles!

Bill

[ron69912t]

I measured the fuel pressure from my stock 69 912 fuel pump at 1000 rpm, it was 3-1/4 psi. This is perfect for the new Webers which need 3 to 3-1/2 psi.

UPS should deliver my new Webers Mon or Tues.

FYI

Ron D

[ron69912t]

Hooray!!

I just came back from the test site and am very happy to tell you all that I passed the emissions test thanks to my new Webers. The HC's were down to 500 from 1100 with the Solexe's. The States max is 900. Way to go.

A 1968 Corvette was in front of me, a very nice car, but he failed the test, too much unburned HC's. He was not a happy camper.

Yea for the 912!!

Thanks to all for all your suggestions and help on this. I am a free man now for two more years.
Ron

[cgarr]

good job!!!! I feel just as you do every two years when I have to pass my 3rd class medical for my pilots license, its gettin harder every year and you never know????? we dont have to do any testing of are cars in our area as yet.

Craig

[Dieselfitter]

As for the strainer in the fuel pump yes there is one on the suction side under the little cover plate on the end with the small bolt in the center. I would not remove it though to look unless you have a new cork gasket for this strainer cover. see ya Mike