Solex 40 p-ll without floats

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Ok ..im telling you we learn new things everyday...I've never seen or heard of solex p40 -ll being used without floats ..looks like the formula vee guys were doing these upgrades looks like it used 3 electric pumps to make them work ..basically by taking out the floats and adding a windage plate and drilling a return line from the bottom of the carb to return the gas back to the tank and you had to use 3 electric pumps ..basically like a dry sump oiling system but a carb dry sump .....has anyone have more info on this setup ... how bad would it be to use on the streets ..I know way way over kill but just curious ...I like crazy ideas and this one seem up my Alley .....here's a link of an old post that I found on Facebook and I was like oh wow crazy idea but just couldn't get it off my mind and I was like yeah this is going on vintage speed on thesamba lol ...yeah I know im bored let me be ...lol link below ..
https://www.facebook.com/groups/formulaveeracingusa/posts/10162498878768115/

[sled]

just.....why?
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[[email protected]]

I was curious on the setup ...I know way way over kill ..I know i wouldn't do it ...just looking to see if other folks seen or heard about this/ that setup ...and if someone does know about it what are the modifications besides the ones I know of ..but like I said i know not much about them because I just seen the post yesterday lol and was reading what folks were saying but not really much ....it would be cool to see how the gas lines are connected and wiring and would and extra battery be needed with 3 fuel pumps stuff like that.. I just want to see and know what folks think.. I like keep my mind with information on stuff like this ...

[SilverThing]

I haven't seen the specific facebook post, but your description sounds a bit like overflow carburetors. The only specific example I know of is the Solex 40 PI used on the very early Porsche 911 (they had issues I believe with throttle bushing wear and were discontinued). I'm sure there are other examples, but I don't know what they might be. I'd love to play with a 40 PI (or a set of four) for a vintage speed engine, but they are a bit rich for my blood even in completely destroyed condition. I hadn't thought about converting a float type carburetor to overflow before, but now that has the gears turning.
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[[email protected]]

[[email protected]]

Here they are ..

[earthquake]

I recall hearing about guys running floatless Holley carbs where they would fit a piece of fuel cell foam in the float bowl and run a return line back to the tank but that's all I remember.

eQ
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[SilverThing]

The pictures do make it appear to be a modification of a 40PII to run floatless “overflow” similar to an early 911. The intent is one pump constantly fills one part of the float chamber, but there is no float to cutoff fuel flow when the chamber is full. Instead the chamber is allowed to overflow to the other half of the chamber and is recirculated back to the tank via another pump. Porsche did that with a mechanical double pump arrangement on the 911, but could be easily done with electric pumps. While more complex than a typical carburetor setup, the benefit is to make fuel mixture more consistent in maneuvers like heavy cornering, where typical float carburetors will go lean or rich because of the fuel sloshing to one side and either opening or closing the float valve. In the case of VWs and Porsches with dual carburetors we tend to get both effects simultaneously where half the engine goes lean and the other half goes rich.

Just speculation on my part, but I suspect Porsche opted to attempt overflow carbs on the 911 because the engine also has a dry sump oil system where the engine is otherwise cable of higher lateral g maneuvers than typical wet sump designs. I imagine that one would need to address shortcomings of a wet sump design on a VW or 356/912 engine if they were to perform this modification and want to get the most out of it. Windage trays and baffles are common mods I have heard of, but I have also heard of weighted pivoting oil pickups to try and keep the pickup submerged as the oil sloshes around. There’s always converting the engine to a wet sump design, which would be interesting.

Jerry, I do appreciate your posts on otherwise obscure topics. For example the discussion we had on Tatra exhaust ejector cooling or the type 367/Petermax Müller engine. Someone is bound to be inspired to try something on their vintage speed project (and hopefully posts about it in the forums). Please keep them coming!
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Thank you for the info ...I like to see or bring back things that seem to get lost it would be sad if they were lost maybe someone would benefit with their problems and maybe see stuff like this and be like oh ok my engine / race car would benefit feom this ..ive never seen anyone post these carb modifications so i had to post it i get it its not for everyone ....I was told in the past that I have radical ideas but like I tell everyone no i dont I just search and search and did I say search for ideas from the past and just bring them back to life ....maybe I should change my samba name to radical idea guy lol jk ...

[[email protected]]

Oh I forgot this question.....it looks like 3 electric pumps were used ..what i dont understand is why 3pumps ..wouldn't 2 work ...1 pump was used to have the gas enter the carbs just like any duel carb setup manual or electric ....and it looks like each carb on these overflow setup each carb has its own return electric pumps to return to the gas tank so 2 total pumps making it 3 pumps ...but my question is why didnt they just use a Y connection/ line with 1 pump to return it to the tank just that would eliminate 1 pump no??? So total pumps would just be 2... 1 enters and 1 for return why do they use 2 pumps to return to the tank ...to me its would be easier using 2 pumps total...

[SilverThing]

You should be able to do it with just two pumps. I can't think of why three would be required or even beneficial, but maybe I am missing something.

One weird quirk of the early 911 design is Porsche put fuel bowls on the intake manifolds that I am still not sure I understand the purpose of. They have floats and valves in them which make me think it helps control fuel flow somehow, but maybe they have a completely different purpose.

I also like finding info on old air cooled engines that might be applicable to us: Tatra, Porsche, NSU, Steyr Puch, Honda, etc
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"I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
"I've seen pictures..." - Jeremy

[[email protected]]

Also to if one were to use this set up and say well they didn't have electric fuel pumps ..yes they did to fit the vintage speed one could use the Auto pulse 500 electric fuel pumps porsche 4 cam engines used these fuel pumps ...other pre 50s cars used these pumps ..so they would fit right in the vintage speed design / correct era parts .... im also shock that I haven't seen anyone who builds a vintage speed engine who eliminates the manual fuel pump and go with these auto pulse 500 electric pumps ....it would help the engine make a little bit power than the manual fuel pump ... dang looks like now folks are gonna buy them up and cost me more $$ lol ....maybe im giving to much info haha jk .....

[Lo Cash John]

I have some info...

Floatless carbs was an old off-road racing trick from the 1970's and maybe into the early 80's. Hot VWs did an article on this mod back in the late 70's. That's where I first heard of it.

Basically mod the carb to have a suction line that feeds to a scavenge pump and returns to the fuel tank. You also add some fuel cell foam or baffle plates in the carb bowl to stabilize the fuel against sloshing. The benefit was stable fuel level in the carb (a very difficult thing in off-road racing) and greater fuel capacity through the carb since you no longer have a needle valve restricting fuel flow and no longer waste space on a float. The fuel level (what we call float level) is adjusted by altering the relative height of the suction line in the bowl.

Years back, when AJ Sims, Clyde Berg and Joel Mohr were battling hot and heavy in the "Kadron Wars" (basically unlimited class except the car must use 2 Kadron carbs of any modification) at drag events on the west coast, AJ was struggling with fuel bowl size and keeping the bowls full. I was chatting with him at his shop and I recalled the ancient article in Hot VWs and I explained it to him. He'd never heard of it but the light clicked on in his head. Next thing I knew he'd adapted the concept to Kads and it solved his fuel trouble.
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[wagen19]

[EVfun]

Wow, it works like a Briggs & Stratton pulse jet carb. For the lawn mower the fuel pump was vacuum operated off the intake pulses and lifted the fuel to a small bowl inside the top of the fuel tank. Overflow fuel then gravity spilled back down into the tank.
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