Solex Carbs

[Grady Clay]

This was posted on another forum ”Solex Carbs” and he needs some more feedback.

“I have a modified early engine running on Solexes and seem to suffer with all the ususal problems of extremely poor pick up and fuel consumption.

We have carefully rebuilt the carbs with little or no improvement and I have just bought a pair of 40IDAs in good condition.

I would, however, prefer to stick with the Solexes if possible.

I see that there is a company in Holland (Duel Motorsport) offering to rebuild/modify Solexes.

Their website claims that when modified the Solex performs very well and gives improved low end performance compared to the Weber and that fuel economy is restored.

As we use these carbs on a Rally car, I am more concerned with performance than economy but I am interested.

I contacted Duel and they gave me a price or $2000 for the mods/rebuild but no detailed information.

I do understand that this may be commercially confidential but for $2600 I can buy PMOs.

Does anyone have any information about detailed mods etc that will improve and solve the standard problems of Solex carbs?

I am not unwilling to pay Duel to do the work but I need confidence that it will be money well spent.

Any comments gratefully received.”

DUEL Motorsport
in Holland says:

“Solex carburettors

All the historic ( 1965 ) Porsche drivers are familiar with the problems of the Solex overflow carburettor.
On race or rally engines these carburettors are notorious for their bad carburetion and therefore bad fuel consumption. DUEL solves this problem by modifying the carburettors, this is mostly done with a complete rebuild of the carburettors and intake manifold.

With these modifications and with the DUEL exhaust system the engine will get a very broad power band, we now run our rally engine’s on full race camshafts without any lack of power in the mid range. Due to the broad power band of out engine’s we have a better fuel consumption, we can use longer gears in our gearboxes and have less gear changes. This all gives the engine and gearbox a longer lifetime which is a must for long distance racing.”

Has anyone had this done? I understand his reluctance to send off for a US$2000 rebuild and modification not knowing EXACTLY what will be done and what the results are.

The “tricks” I know about Solex are the sinking floats, fuel overheating, venting the float chambers and overflow chambers outside the carburetors and fuel cell foam in the overflow tube. Solex carb & cam engines are very sensitive to exhaust systems. They also work best with slow application of throttle with lower rpm as they tend to act like “too big” of a carburetor.


What mods do Pelicans know?

Best,
Grady

[davidppp]

Well asked, Grady.

Bump..I'd LOVE to know more Solex lore..

Did the factory Sport kit solve any of the problems?

Kind regards
David

[RoninLB]

no personal info. Only what may be mentioned in Up-Fixin.


btw PMO's are a carb dream come true imo.
Extremely accurate metering and equalization among all 6 throughout the rpm range based on computer EGT readings on the street, not dyno. Stability of EGT and decreasing deviations among the 6 above 4k rpm in 4th & 5th gear than below 3.8k rpm. Below this 3.8 rpm the deviations are still below 75F deg, usually around 50F.

[jluetjen]

Grady. This is going to be a mightly lonely thread. The last time I checked one of the "Early Car Owner's Age" surveys, most of the guys on this BBS weren't even born yet when Porsche got wise and pitched the Solex's for Webers. Heck, I doubt that their parents had even met yet! You'd have just as much luck asking for first-hand experiences from WW1 vets!

[DaveE]

I'd be very interested also. My '65 still had the original Solexes when I found it and they suffered the usual flat spots. I have a pair of Webers but would really prefer to use the original Solexes if possible, when it's back together.

[davidppp]

Hello chaps.

I hope sdomeone may have some help to offer on this..The problem has been solved, somehow....see the www.duel.nl site..

Kind regards
david

[kenikh]

I also have read that Biekert Engineering in Oregon can do the Solexes right.

http://www.biekerengineering.com/

Researching now.

[austin552]

Sorry, I am still stuck in Zenith Hell...

[911quest]

Most of the running problems are the same as the Weber's the carbs are just old as dirt are tired and worn.....

That 2k probably get's you new throttle bushings which is 85% of the problem with all the Solex's and the Webers out there. I believe the one internal change is the emulsion tube's on the Solex's.

[denton]

Just a note re Duel: these guys enter early 911's at Spa every year for the Spa 6-Hours race, & almost every year they are the first 911s home - these are 'proper' race engineers. They get well over 200hp from Solex carbed 2 litre cars, so they really know their stuff: not cheap, but then the best seldom is. We ran against them a couple of years ago, and their cars are seriously quick and well prepared .

Hope this helps.

Peter R /
early 911 FIA racecar (ex Gerhardt Mitter / Karl von Wendt)

PS I would like to buy a good set of Solexes & manifolds - anyone out there selling? contact via Pelican or to peter@rampartsecurity.com

[denton]

If you despair of the Solexes, let me know... I would love to buy a set for my FIA race engine.. regards Peter ' denton ' at Pelican, or to peter@rampartsecurity.com

[denton]

Also:- easiest & most effective mod for Solexes is to make sure the small restrictor hole in the fuel supply union at each carb is not still sized to 1mm - as they left the factory. This guarantees fuel starvation when used in anger. There was a factory mod published late 1965 to drill them out to 1.2mm, we have found that for racing (long periods at full throttle / high revs) 1.3mm is a minimum.
Also use Pierburg-style circulation pumps to supply the carbs 'downstream' of the float chambers, and don't over-pressurise the floats - they can't handle more than about 3psi, and will flood the fuel system if over-supplied.
Jet sizes etc depend on cams, exhaust etc - you'll have to experiment.
Hope this helps.