I had a test drive and after a few miles the car stalls with fouled plugs again. I have dual Weber 40 IDFs with an 009 dizzy and an after market coil from my FLAPS. The timing is right on and the dwell is fine. After cleaning the plugz away I go for a few more miles. Idling they even foul after a few minutes. If I start turning the idle mixture screw out I start to get poping thru the tail pipe, which sounds like a lean condition, but after a few minutes the car stalls with fouled plugz. The car really hasn't idle very smooth. Could the pump by-pass valve be the culprit? I had this thread before and still can't get the car to run right.

1st - what kinda of fuel pump?

2nd - Do you have a regulator in line?

Street carbs - 3.5 to max 5 psig

You may be over-riding the float valves and flooding.

Prolly not jetted right, too....

Pump bypass valve? Not sure what that is.

It can still be an ignition problem. What plugs are you running?

The by-pass valve is the valve at the bottom of the fuel bowl. I have a new rotary fuel pump from CB that has a built in regulator. (I do have a facet laying around somewhere). I an running Bosch plugz. My jets are Main = 115, Idle = 50 not sure of the air.

Which Bosch plugs? The exact model (the heat range is important).

If you watch your engine running with the aircleaners off, do you see fuel coming out of the accelerator pump nozzles while idling?

I have to check both those questions

Turning the idle mixture screw "out" makes it richer.

Have your tried following one of the guides at aircooled.net on how to set up your webers?

That would be a starting point.(after you make sure you have correct fuel pressure)

Have you synchronized the carbs? What size engine is this?

The engine is a 2056 ('originally '70 1.7). I have tried to sync the carbs and actually get pretty close.

Synchronizing can make miracles.

But, you are right. Carbs are from

I love carbs, but I'm doing the "Atkins" thing right now, so they are evil.

Oh, wait...

Carbs are not that tough, sounds like your jets are fine for that sized engine. Other things to consider as mentioned would be the plugs. If you are using Bosch, a heat range of 7 should be about right for a driver.

Also as mentioned, you don't need more than 3.5lbs of fuel pressure. Anything more isn't needed as long as your pump can keep up. It is easy to out "force" the floats. It sounds like you are close, keep at it.

You may also be getting weak spark. Sounds corny, but grab a stock coil or one of the 0012 coils and see if that makes a difference.

I was reading the How to jet your carbs article from Aircooled.net and at the end they say that the accelerator pump could be suppling to much fuel. You can turn the pump screw to adjust. I found a pic of the new Weber 40 IDf and were the adjustment nut is. Problem is I have the old version with the roller, were is the adjustment on these suckers.

You can change the pump jet itself, as well. I think this is what you're calling the bypass jet.

It's not uncommon, particularly with the roller types it seems, to have the pump nozzles dribble some fuel even with the throttle closed. If you look down the throat and see some fuel coming out of the nozzles, pull up on the linkage to force the throttle to be completely closed. If the dribbling stops, your linkage is holding the throttle slightly open (or you have the throttle stop open too much), so adjust as necessary. The nozzles are held into the bodies with screws that, if loose, will also cause some dribbling. If you can stop the dribbling by closing the throttle stops, but that causes the idle to be too low, then use the air bypass screws to add a bit more air. If you can't stop the dribbling by adjusting the throttle stop or linkage, then you may have to grind down the cam a touch to add clearance at the roller. This is a last resort, obviously. Once you take some off the cam, you can't add it back, and I have no idea if these cams are available as separate parts.

As others have noted, if you've been turning the idle mixture screws OUT to adjust, you're making it richer, not leaner. Turn them all the way in until they're lightly bottomed, then out 2.5 turns. With the engine running, turn them in until you the engine starts to stumble, then back out 1/4 turn. You're now at the lean end of idle. If you have to turn them out more than 2.5 turns from bottomed to get a good idle, your idle jets are too lean. If you have to turn them in more than 1 turn from bottomed, your idle jets are too rich. Since you have 50 idles in there, they're not likely to be too rich until you have fuel leaking out from somewhere else.

First you must throw that shitty distributor away. Get a stock 205 Dizzy for a 1.8 or 2.0 engine. Put some sort of magnetic or optical pickup in it (Pertronix or Compufire). Leave off the vaccum can (it can be run as a centrifigal advance).

Toss the Bosch Plugs in the garbage and get a set of NGK B7ES plugs, you might even try a set of B6ES to get the car tuned. You must then go through the standard procedure for setting the carbs up as listed here: http://www.inglese.com/tech.htm.

Once your carbs are synced you MUST make sure they are opening at the same rate and the same amount. I spent several hours on just making the linkage open each carb at exactly the same time. The more time you spend getting this perfect the more enjoyable the drive will be. My car drove like my stock injected Honda when I was driving it everyday.

Set the valves first before you do anything else. I use the procedure:

Bring #1 up to TDC adjust #1 INT & EXH, #2 intake, #4 Exhaust
Rotate the engine 180 degrees to TDC on #3
Adjust #3 INT and EXH and #2 Exhaust. Set them all intakes to .005 and exhaust to.006


90% of carb problems are found in the Dizzy. I would start the car and bring it to operating temp, and start making carb adjustments.

Brett,
Have you had trouble with #4 intake when using this method?

Nope 17k Miles without a single problem. Too bad I wrecked the car.

uhhh.... your instructions don't include #4 intake

You mean they didn't tell you about this secret when you bought your 914? I thought everyone knew about this.

Number four never gets adjusted

Sorry I left that one out. Adjust number four intake when you do #3int and exh, #2 exhaust, #4 intake.

I don't know if any of you are old enough to remember this, but, several years back there was a guy who developed a carb. that had like 1/3 the parts, was self adjusting for altitude, and gave better gas mileage by more effeciently mixing the fuel with the air. Before he could market it the "BIG FIVE" got a law passed making it illegal, so he could only sell it for the track. Ring a bell? Anyone know what happened to the guy and his product?

sounds like another urban myth

they probebly didn't want to spend the money to get it C.A.R.B legalized

variable venturi carbs....Preditor makes them....nothing new, been around for 100 years or longer, some better than others

Ford experimented with them as well, ran great if you knew how to tune them, if not, you're screwed and will hate them....they died when FI became more used by the factory

there is also supposed to be some "fish" carb.....sounds great, but it's pure BS until I see real testing results and not from one of his groupies

No, no myth. The major auto makers made sure legislation was passed making it illegal to modify the factory fuel system, right after this guy developed it. It left him with thousands of units and a limited market. Technically, carbed 914-4s are illegal. But because it costs too much to correct the fuel system I think they become exempt.

Bob I gotta wave

Because if that legislation where still in action then every major fuel system component manufacture in the world would be breaking the law. SEMA even supports these companies. As bad as manufacturers are about filing lawsuits, if such legislation exist it would be a lawsuit fest nowdays.

yes, for street use (not sure about all states), at least here in California, even a '70 914/4 "supposed" to have the fuel injection

There was some extensive writeup on the Fish in some British tuning books. They were interesting looking, with a fuel control that was entirely tied to throttle position. The fuel came out of the throttle spindle, through small drillings in it. Looked like it would provide decent atomization, but didn't seem to have any other major advantages.

The bit about some suppressed high-mileage carb is an old, old story, and is simply not believable. If the guy had filed a patent on it, this would be a matter of public record and would have been found by someone in the last 50 years (this story is that old, and it's usually the oil companies, not the car companies, suppressing it). If he didn't file a patent, the technology would have been stolen by someone else by now. Fuel efficiency is a huge seller in many markets (Europe, for instance), and it makes no sense for the car companies to suppress it.

Conspiracy theories work best when it actually appears to be in the best interests of the powers that be to do whatever it is they're supposed to have done. This story simply makes no sense. The timing also doesn't work, as there are published accounts of this story going back to the 1950s, yet the emissions regulations that forbade altering the car's intake systems didn't pass until 1965-1968, and the car companies fought it tooth and nail.

And who are the "BIG FIVE"? At the time these stories started to circulate, GM, Ford, and Chrysler totally dominated the US car market, and had been referred to as the Big Three for quite some time. Throughout the 50s, the US car market was gigantic compared to any other market, so for all intents, the Big Three controlled world car production. Nonetheless, they so ignored other markets that our intrepid inventor, after being suppressed by the Big Three, would have found ready buyers for his technology in Europe. The French and British automakers would have snapped this up and made extensive use of it in the 50s. One has to remember that at the time, the typical European car had an engine under 1 liter for fuel efficiency, and there were a large number of cars with 750cc or smaller engines on the Continent. The most common version of this story tells of a 100mpg carb tested on a normal American car of the day, which would have had a six or eight cylinder engine in the 3 liter or larger range. If the Europeans could have made 100mpg cars, they would have. Even the 750s struggled to do better than 40mpg, and only under very light loads.

Finally, the story makes no sense thermodynamically. The inefficiency of the Otto engine (only 15% of the energy content of the fuel is actually used to make the car go, 70% of it goes right out the exhaust) isn't caused by its fuel system (or, at least, not by that alone).