Two original versions of the P78 tool

[Joao Filipe]

Hello there, question: Are there two original versions of the P78 tool?

1 - Harry Bieker wrote in his excellent article for Registry (Tuning Solex 40PII-4, Set/2010) to set the fuel level: "Be sure to remove the jet from the carrier and install it into the end of the gauge before installing the gauge" (...) and, after setting the fuel level, “don't forget to remove the jet from the tool and install it back into its carrier".

2 – In the 356 Factory Workshop Manual / Checking Carburator float level with the P-78 - they don't mention it (as there was not a jet to be moved from the carrier to the tool and vice-versa).

Well, in my new aftermarket P78 (from Pelican/Stoddard parts) in the photo, the main jet cannot screw in the gauge (!)… How can I perform a running test? Has the tool (T80-780-000) a wrong design?

Many thanks!

[C J Murray]

The car will run fine on the idle jet. No need for a main jet.

[Albert Tiedemann]

I have seen two designs of this tool of the interface in question. One design of the tool accommodates the main jet and the other does not. In the OEM version of the tool that I have, there is no provision for the main jet. I made clones of this tool many years ago and the supply has been virtually exhausted. There are two major design challenges in producing/reproducing the tool.

First there is the sealing of the "sight glass" and the second is finding an appropriate sight glass material that will not succumb to the ravages of deterioration of the newer fuels. I have investigated many plastics for suitable material. Claims are made by some producers to have no visible effect from agents likely to be found in the currently blended fuels. But, such materials are costly and the quantity that you would need to buy for a modest run is significant. Engineering samples or even offers to buy same fall on deaf ears. It is like going to a machine shop with an order for a small run of a new tool. Most places want to make at least 50, and for some applications, there are not that many enthusiasts that will purchase a quality tool for the task.

The tool shown takes considerable license in producing a clone based upon an OEM sample. Effective sealing of the sight vial to the tool body appears to have been via o-rings but the edge distance of the sight vial is far too thin. There is no need for such a thin section. It should be a full radius. It will crack in time. I have made many replacement vials for Factory [OEM] units that presented such a thin interface. This was one of my first improvements on the design and embodied in the units that I offered.

[John Brooks]

I have an old P-78. Mine has a relief for the jet carrier.

I made up a test bench many years ago when I was doing lots of carbs. I use a spare manifold to match the carb. I used the gas tank off a weed whacker. A small battery and 12v low pressure fuel pump. (Al and Brad have this type of pump)

You rebuild the carb, the put this test stand on a level bench. Bolt the carb on finger tight. Adjust the floats, accelerator pump stroke, leak check all on the bench. All you need to so is tweek the idle jets on the car. Even when I was a kid the marks on the p78 were hard to see in the car, same for the test tube under the pump squirter. I got too old to do this in the car, but the bench still works.

There is a 5/16 rod welded to the plate, it goes through the center manifold bolt hole. I use a spring and ball knob, to hold the manifold down and level. You can lift it up and turn the assembly to access the far side. Probably cost under $100.00 to build, even if you don't have spare manifolds lying around. But that is much cheaper that setting the engine on fire from a leak. It works for the old 911's also. It just makes the carburetor process so much easier, even if I only use it every couple years. Also Reduces the number of off color Italian hand gestures needed when working on Webber's

[Ron LaDow]

I used another approach and I can't find an image on this computer.
Fasten a worn-out timing cover to the face of the bench, find a decent distributor drive 'stub' and fuel pump; fit them.
'Hose' as required (I used manifolds as carb mounts also), stick a 3/4" spade bit fitted to a drill motor down the distributor hole until it drops into the grooves on the 'stub', crank it up.

Hey, Ab! Are you coming to the Lit Meet?

[John Brooks]

Ron

I have done that to check fuel pump pressure after a rebuild. I like pressing a button for the electric pump. Some where I have a M12 banjo bolt with a 1/8" NPT in the end, to check fuel pump pressure at the cab in the car. One of those things you make and never throw away.

[Albert Tiedemann]

Hey, Ab! Are you coming to the Lit Meet?

Thank you for the thought, Ron, but as in years past, I will not be able to attend.

[Albert Tiedemann]

Thanks for posting that picture of a real P25a. Its the only tool that would fit between the injection nozzle and the 24 mm venturi on the Zenith 32NDIX used on the old 1600 N engines. This was because it was an oval shape. With the rage for power these days, you rarely see this application. The original P25a was a very thin oval "test tube" with test tube engravings for the volumes. It was also very, very fragile because it was glass. If you compared what is offered today for "P25a" coupled with the hefty price, you will find that it is far too long and too heavy and too big in diameter. I made special sized, plastic, calibrated versions of P25a back in the day when P25a was selling for about $25[wow!]. The newer blended fuels ruin most plastics used in this application BUT a real P25a still works well because it is glass.

[Joao Filipe]

Hello there. Now I´m happy and grateful to all of you. Knowing from Albert that there was two (!) P-78 versions of the tool (with and without main jet on the tool); from John the way he used to do it (thanks for the precious photos – I had never seen a true P25); from Ron an “unusual” approach; and finely from my ingenious brother who turned the version 1 in to version 2 with his lathe. Easy task - for him, of course!
Now I will show you the tool result. Later the “dynamic” test, I hope (with and without main jets for CJ Murrey )
Thank you!

[Joris Koning]

For giggles i dug some of mine out. Poth the P77 and 78 have small changes over the years. Jon B would be the one to ask

[Albert Tiedemann]

That is quite an array of variations in the gauges for the Solex and Zenith carburetors.

My Factory "variation" of P78 is the third from the bottom shown in the photo. If you look carefully, the principal change in those shown for P78 is the method of retaining the "loose" section of the tool, that being the metal section that is captured between the carburetor housing and the sight glass. Apparently no retention method was used in the bottom one, a screw in the 2nd from the bottom and in the third, a short cylindrical slug captured by a circumferential ring in a groove. You will find an application of the ring in the emergency jack as well. Effective sealing of the loose section to the threaded one is compromised in each progression of the tool and the latter one requires the most protection of migratory fuel in the transfer process. Erosion of the carburetor housing interface aids in promotion. With aging carburetors, an o-ring seal at the carburetor interface instead of fiber [original issue] seems to work well.

The sight glass material may also have been changed as mine has about the same hue as the 3rd from the bottom. Those still "in the bag" appear to have the circumferential groove.

I am looking carefully at those presented as variation or subtle changes in tool P77. Those illustrated as applications in figures in the shop manual seem to have been turned at one time from hexagonal stock because this is evident in the photo/figures [which they rarely change] throughout the production of all the shop manuals if the gist of the photo is relevant.

No, in nearly 55 years I have not handled a P77 with a hex section that came in a tool delivery to a Porsche Dealer or in a bag obtained over the counter from a Dealer. Could this be the prototype [or sample sent for approval] used just for the photo for later inclusion in the manual?

[Joris Koning]

Ab,

The hex shown is actually a nut holding various fiber and alu sealing washers to the tool. A mechanics trick from back in the day I would imagine.

[Olivier Auvray]

1) It's not necessary to put one jet into the tool.
2) To adjust correctly the float level, the needle valve must be in motion (regular cycle "open/close").
3) The fuel pressure has a lot of effect on float level; if you adjust it on a bench, you need to be sure that, on your engine, the fuel pressure is the same.

regarding points 2) & 3), float level adjustment on one running engine is the best way for the best result............. don't forget your fire extinguisher!

If you're working on a bench, check fuel pressure and find a solution to consume fuel.

Please, check the following photo:

It's not for a Solex 40 PII.... it's for a Zenith 32NDIX
It's not a Porsche factory tool.......... it's a Zenith factory tool
It's made with a real glass tube (modern fuel has no effect on it)
It has something like a drain plug to create a fuel consumption!

[Joao Filipe]

Hello, I´m back. Thank you Joris for showing us your P77/P78 surprisingly collection. Congratulations. Now I know that were made small changes (not only two) all over the years. Albert emphasised for us the differences, thank you.
Oliver surprised us with "no jet into the tool" but I think he refers to a static test. Besides that he said us not to forget: the fire extinguisher; to pay attention to the position of the needle valve; and, very important, check and recheck the fuel level with different fuel pressure; and it must have a consumption…
With a Solex in "Power Metering" (normal operation) the fuel needs to flow through the main jet (be calibrated) to reach the venturi. In a working mode, with the right fuel pump pressure and consumption, the level must stay there (as the fire extinguisher). Next move.
Today I have done a static test (with my bench levelled – John’s advice) and set the right (?) level with the P78 at near 6 PSI in dial gauge. Well, no fuel appear in the inspection port although I was expected it will happens as 2.5 - 3 PSI is the usual working pressure. Am ´ I right? I will recheck the level later.
By the way, I feel that my previous topic (Insulating spacer for the Solex 40 PII-4) and the present should come together. It is here:
viewtopic.php?f=1&t=40752

[John Clarke]

Hi all
Why was there ever a need for this Gauge in the beginning? What was wrong with the plugged float chamber hole that Solex provided? Seemed a very simple method. Was it originally OK with 'Old Fuels'
Jay