The Solex B40 PA4IO-5a Carburetor thread!

[B.S.F.]

The thread for the vacuum pipe appears to be M6, which makes sense considering SOLEX is or started off as a french company. I think all the bolts on the carby are metric.
.M.

[JDNSW]

Both Solex and Zenith are originally French, and all threads are metric - but I would not bet on them all being ISO metric!

John

[EISTO]

Chris; excellent suggestion to use the 13mm boss. I think that's what we'll do. Also, the position of the small hole in relation to the butterfly is a very important point. I'll have a close look to make sure I get it right.
Just ordered a 3mm hose tail from ebay.au. This one has a standard metric M5x0.8 male thread, which leaves plenty of room inside the 13mm boss.

And yes: I was convinced that all threads were UNC or UNF, but just as John and M. say, it looks as if they've used metric threads. What I thought was a 5/16 nut on the throttle spindle appears to be a 8mm x 1mm metric fine thread. This remains to be confirmed, though. They are very similar; the M8x1mm pitch is almost exactly the same as for 5/16 UNF (25.4 instead of 24 threads per inch).

Br,
Einar

[Busted Syncro]

G'day Einar,

Yes the Solex is all metric thread, designed in France and in 1925 Gordon Richards started manufacturing Solex in England. All still metric.

The spindle thread is M8 x 1.00. I would run a full nut with lubrication over the threads to clean them up. Also be careful when starting the nut because of the two flats. It's easy to cross up the threads.

The use of the Boss with the 1.5mm hole into the throat will be 20mm below the original vacuum port and is well clear of the throttle plate. It will be a compromise however, in the circumstance it's the best you can do.

Chris

[EISTO]

Hi!


The carburetor has now had a thorough clean, involving thinner, red ethanol, ultrasonic cleaning bath, brushing, rubbing, swearing....you name it. It still REEKS of petrol, though . There was an incredible amount of copper/aluminium rust and grit inside the body, but I managed to clean out most of it and used compressed air to make sure the ports were not blocked.


Chris: by veeeery careful drilling with a 5mm drill bit we managed to remove the remains of the old screwed union and the olive . We then cleaned up the old threads and inserted a hosetail with M6 thread. Phew! Did exactly as you said and carefully cleaned up the M8x1 threads on the throttle spindle and starter valve lever with a new nut. The nut enters quite easily now.


I noticed that -at closed position- the throttle butterfly more or less blocks the ports for the vacuum system. It clears the ports by around 1mm. I've assembled the spindle exactly the way it was, so I guess it's supposed to be that way.

Of course, while taking apart the starter valve, I managed to lose the 5mm ball, but luckily, I found a replacement.


It's becoming more and more apparent that some ham-fisted DIY'er with undeserved self confidence has given the carb a hard time using the wrong tools. I discovered that the emulsion tube is broken, and I guess there's nothing we can do about it. Perhaps the carb will have to be replaced anyway, but we'll at least test it before we write it off.


/E

[Busted Syncro]

G'day Einar,

Gee you have been busy. Good work to reuse the M6 port. When it comes to old Series Landrover, ingenuity is the key and a never give up attitude.

The throttle plate position depends on the idle slow speed adjustment screw and will just clear the vacuum port depending on the idle speed set.

Bad luck with the emulsion tube. However can you post a picture of the broken bits for us. Is it the brass tube or the diecast spraying bridge or the spraying orificies bit?.

Chris

[EISTO]

Hi Chris,
Yep, once you get started it's too fun to stop. I love this type of project; for every challenge there is the additional satisfaction of solving the problem


Attached are pictures of the emulsion tube and spraying bridge (choke tube removed). My description wasn't that accurate, and to be honest I'm not exactly sure which role these parts play. I''ve given myself the homework of researching this.
Anyway, it's the spraying bridge that's broken. The emulsion tube is intact, and the correction jet is of course missing. I guess the issue is how to get hold of a correction jet and find out how to attach it to the broken spraying bridge.


Einar

[Busted Syncro]

G"day Einar,

Thank you for the photo's.

It's bad news and good news.
The broken spraying orifice is removable from the spraying bridge and is replaceable.
The bottom of this tube is a taper fit into the spraying bridge.

However, it could be difficult or easy to remove so only use light twisting and pulling otherwise you may break the spraying bridge. Maybe WD40 here as well!!!

You need to find another Solex to use for spare parts. Europe was popular for Solex so maybe wrecking yards might turn up something.

Hope this helps
Chris

[EISTO]

Hi!
Unfortunately, Norway was never big on Land Rovers, and the odds that you'd find an old series car hidden away in some scrapyard, are unfortunately pretty slim.
Spoke to my cousin (the owner) and we decided to take our chances on a custom repair. We chickened out on removing the spraying orifice/column despite soaking it in WD-40 overnight. It didn't budge and I couldn't risk using any force.

It took a day or two to think this through and try to find a patent that could (potentially) solve the problem. This is what we came up with:

We had to find something -preferably made of metal- that could serve as an airtight coupling between the broken cast spraying orifice and the jet itself. It turned out we already had a new jet, as it was included in the solex repair kit.

Then I came across some copper support inserts for copper tube compression fittings. See Attached pictures. They are about 30mm long and 10mm in diameter. The wall is just 0.8mm thick, and they are perfect fit for the diecast column. Had to use a bit of force to press it on, and there's no visible gap.

The jet has a standard 6mm thread. We took a 6mm nut, filed it down to about 8.5mm in diameter using a battery drill and a file, and then pressed it into the copper insert, adjusting the height correctly. And that was that. A drop or two of loctite will make sure it's airtight.

Since the copper tube is slightly larger in diameter than the old (intact) spraying column, it reduces the effective cross section of the choke tube (not mounted in pictures). A guesstimate says 1-3%, depending on where you measure. Hopefully, this doesn't affect performance significantly.


The carb will be installed in a couple of weeks (the car is 1500 miles away) and I can't wait to see if it works.
I'll keep you updated


Einar

[Busted Syncro]

G'day Einar,

Very nice solution and thank you for posting it.

Couple of things to note.

Don't use a gasket under the air correction jet. The seal that you want is between the brass emulsion tube and the air correction jet. Also as you are aware of, don't over tighten the jet.

I note it is 180 (1.8mm hole). This will give you a slightly richer mixture over approx. 2000 rpm.

The sight decrease in air flow can be compensated in selecting a smaller main jet however, the jet sizes are only 0.05 mm apart in diameter so size is very critical regarding fuel consumption.
For a 26mm choke tube the standard main jet is 120 (1.20mm hole). So in your beautiful and cold country the original main jet is maybe what to use.
See how it goes regarding fuel consumption.

Also the pilot jet must have a gap between the brass hex and the casting. The seal here is the tip (nose) of the jet and the casting. You can check that the jet is seating on the nose by using a gas lighter to put carbon on the nose and seating it and noting the contact ring.

All good
Chris