Who to rebuild Solex carburetors?

[YTNUKLR]

I have a set of Solex 3 barrel 911 carburetors that I'm using on a 2.0L vintage racing engine, but they need to be gone through.. Does anyone have any experience or know anyone who rebuilds these? I could probably do it myself if there is a parts source, too.. Thanks! Scott

[jhora]

Scott,

I just purchased a Solex rebuild kit from Stoddards.
Go for it...you can do it!

John

[one-two]

John, what's in that kit, if you don't mind me asking? Anywhere else that carries Solex spare parts that people knopw about? Thanks

[Type911]

Give Harry Bieker a call. His shop is in Grants Pass, OR.
Well known guru of Solex carbs.

http://www.biekerengineering.com/

[preS]

Scott,

In an old thread this has been discussed before. Just a rebuild kit is enough to get it run right, especially when you want to go vintage racing.

There is one shop that I know off, located in the Netherlands. They are going by the name of DuEL and they have sorted them the way they should be. Even the Germans send there carbs to them ..

Just my $.02

Richard

[Schläfer]

I’ve seen a few threads about Solex, so I thought I'd share my experiences of these carbs. There's a lot of black magic surrounding these carbs and quite a bit of miss-information. There's no reason why they can't be rebuilt at home with some decent tools, a parts washing tank/carb cleaner and a lot of time. I’m sorry it’s so long, but there’s a lot to tell.

This is what I did once everything was removed from the car. Firstly soak everything in Plusgas/WD40 to make sure everything will come apart easily. Care must be taken with the very small 5.5mm adjuster nuts for the acceleration pumps, it is quite easy to snap the rod if you're not careful or the adjuster has rusted on. Once it has had a good soak, strip everything down, be methodical and bag all of the relevant screws and adjusters together. The carb itself consists of the main body containing the throttle shaft and valve, the acceleration pump/reservoir, the carb top, which has the acceleration squirter, the main venturi and the jet pack. Start off by removing the jetpack, this has two slotted screws, which is visible from the top of the carb. The screws don't come out all the way, so just undo them enough to extract the jet pack from the body, next you can remove the carb top with the four slotted screws at each corner. Next undo the 13mm lock nut on the side, undo the screw and then remove the venturi. It'll probably be well held in so give it a good soak and plenty of wiggling. The accelerator pump is mounted on the side of the carb with four short slotted screws. The carb should now be pretty well stripped. Take the jet's out of the packs, make sure all of the gaskets are removed, but don't throw anything away!

Next is the time consuming bit, you'll need to clean everything. Personally I put everything into my parts cleaning tank, I put all the big stuff into the bottom and wash all of the small (Losable) bits by hand. Give everything a really serious clean because cleanliness is everything with these carbs. Once it's all had a good clean rinse with water and properly dry everything. Use an airline, oven, hairdryer or whatever you can get your hands on.

OK, now it's time to check everything. The first thing to check is the throttle shafts, they should feel really smooth but not too tight. If there's any play in the throttle shaft or it's a little rattly it'll need to be rebushed, otherwise you'll never be able to tune out that problem. It may be possible to ball race the shaft but it's probably unnecessary. If you do need to rebush the shaft, you'll need to carefully grind the threaded side of the throttle valve screws so that you can remove them, undo the shaft and it'll pull out from the side of the carb. The next check you have to make is that the ball valve in the accelerator pump is working, it's quite a common problem for it to seize, especially if the car has stood unused for some years. The best was to check is to put your mouth over the area and give it a suck and blow. It should draw air from the jet pack area and blow out of the hole that lines up with the squirter tube (that's the one that points into the carb). If it's clear then great, if it's blocked get a big pot and boil the carb body in water for ten minutes or so. It should clear without too much drama, you can also GENTLY tap the surrounding area and gallery with a soft mallet while it's still hot. Remember mind those fingers it'll be hot! I had a really tough one, which wouldn't clear by boiling in the pot, so in the end I used a nozzle off our steam cleaner and blew steam down the holes and that cured it. A symptom for driving the car with a blocked ball valve is it feels like a misfire at low RPM that clears over 3-3.5k RPM. Next check the idle adjustment screw. These are made from brass and very easy for some spanner monkey to over tighten. It should look like a perfect cone, if it has any grooves use the new ones from your rebuild kit.

OK onto the build.

Rebuild kits: You can get a new kit from and number of specialists, it’s not available from Porsche as a kit anymore, but if you can get an original NOS Porsche one it makes sense for a numbers of reasons. Firstly the new kits are missing the gaskets for between the base plates and carb top and the gasket for the float chambers. These gaskets are still available from Porsche singularly but cost $$$'s. The new kit also comes with black accelerator pump diaphragms that aren’t as good as the originals and have been known to fail, they seem to break down after a period of time. The old Porsche ones are red like the mech fuel pump diaphragms and really last a long time, if you're original ones are useable then great!

OK, start by laying everything out in order and build one carb from start to finish at a time. Don't be tempted to use any sealing compounds it'll be a mistake, the gaskets should go on dry. Pop the venturi back in first, then the gasket and then the carb top, it's obvious which way everything fits together because of the slots cut in the venturi for the squirter tube. Tighten the screws down in diagonals so everything pulls down nice and evenly. Rebuild the jet pack, it'll only go back together one way because all of the threads are different to stop any mix-ups. A small keyhole shaped gasket fits onto the bottom of the jetpack, and that small rubber O-ring you've been wondering about slides up from the bottom the that shoulder on the jetpack. This O-Ring is one of the single most important items, If you get an air leak between the carb body and the jetpack because the O-Ring isn't seated properly then all of your mixtures will go straight out of the window. Use some light oil like 3in1 on the O-Ring and it’ll make a good seal. Care must be taken fitting the jetpack to make sure everything fits together happily. Screw the jet pack into the carb carefully, it'll need to be NIPPED up tightly, but DO NOT over tighten it otherwise you'll bend the ears on the jet pack. Next it's time to refit your accelerator pump, this consists of a spring and diaphragm. It draws fuel into the pump as you lift off the throttle, then squirts it out as you accelerate. Again make sure the spring and diaphragm seat correctly and you tighten evenly, don't forget to pop the adjustment rod through the accelerator actuator and loosely spin on the adjuster and lock nut so there’s about 1-2mm of thread showing on the rod (make sure all 6 carbs look the same). Screw the idle adjusting screw in all the way, preferably by hand and back it off about half a turn. DO NOT over tighten it otherwise you’ll instantly need another. OK so now you have one finished carb, do the other five and we can carry on.

The next thing to turn your attention to is the manifolds. They’re made from magnesium alloy and can pit quite badly inside. Make sure all the spill tube galleries are clear and that they’re generally in good health. It may be necessary to reface the float chamber reservoir, because they’re die cast alloy, warp and have a tendency to leak with fuel sloshing around inside. Make sure the floats are healthy and that the shut off valve is working correctly. If you’re happy then it’s time to refit the carbs to the manifolds. It’s worth paying attention that when you start assembling the cross linkages that all the throttle valve adjustment works the same way, otherwise it’ll get very confusing when it comes to synchronising everything. Once you’ve got the first bank of carbs assembled with linkages connected, make sure that all the carbs close together. It’s a visual way to get things synchronised, which will help when you come to start the car later on. Replace the air cleaner base plate, but DON’T refit the velocity stacks. Build the second bank of carbs and it’s almost time to refit to the car.

Before you do anything else, your mechanical fuel pumps will need a quick clean. Remove the small bolt holding the front cover on (get a cloth to mop up the spilt fuel). There is a small screen filter in each pump. Give it a good clean, as you don't want any poo pumped into your nice new CLEAN carbs. It might also be a nice idea to use a new fuel filter from your Bendix and write your current mileage and the date on it with a marker pen.

[Schläfer]

OK get everything connected, all linkages and fuel lines. Once you’ve done that, check everything again, believe me it’s worth it. If you’re happy your not going to have any fuel leaks switch the ignition on so that the electric Bendix fuel pump is running. It’ll tick really quickly at first until it builds some fuel pressure. If it clicks for more than a couple of minutes or so, there may be an airlock from the tank. This can be overcome by applying some LOW pressure to the tank breather, but as soon as the pump picks up, drop the pressure. If anything’s going to leak it’ll do it now. My advice would be once you’ve got fuel pressure, switch off and check all the fuel hoses for leaks. If everything’s dry we can carry on. You might need a friend to help start the car while you operate the carb linkage because by the time you’ve ran around from the drivers seat to the engine bay it’ll no doubt die. Don’t expect a rock steady idle, that comes later. I’ve found that the trick with tuning these carbs is that you need to remember they are six independent carbs and treat them as so, the bigger trick is making everything work together at the same time. First things first, get the engine running and start by synchronising the throttle valves with your Unisyn, (it’s about the only thing you’ll fit into the engine bay). To make it easier wind on the throttle stops a bit until you can get the engine to about 2k RPM. Once the throttle valves are in sync, things will start to run much smoother. This is the bit that everyone seems to miss. The volume of fuel must be measure from the squirter tube. The workshop manual gives a method of hooking up an elaborate additional fuel pump so that you can measure the amount of fuel that the acceleration pump delivers. Everyone I’ve spoken to has the opinion of making it look the same and it’ll be alright, this is where the REPUTATION comes from, guess what, it won’t. Just because the adjusters look like they’re in the right place, the performance of each spring/diaphragm can be quite different. I think there’s also a slight flaw in the factory’s method because it’s adding an additional pump that isn’t in use once the engines running. I have found that there is a method to measure the fuel volume with the engine running. This also makes sure the mech pumps are doing their job too. The velocity stacks must be off at this point which is why I recommended they weren’t fitted yet. This is where a special tool must be used. This is available from http://www.biekerengineering.com/ I use an old original one, but believe me this little vial is worth its weight in gold, there’s no other way to do this. The vial needs to be held underneath the squirter tube and the carb must go to wide-open throttle and back twice. This will give you enough fuel to measure. Remember these six separate carbs must deliver the same amount of fuel at the same time. The way to measure this with the engine running is to disconnect the linkage from the carb you’re going to measure so it’s independent from all the others. You can now actuate that carb to WOT and back, catch the fuel and measure it’s output. There’s a summer and winter volume in the workshop manual, but to be honest I’ve found it better to find a starting point, drive the car and you’ll feel if it’s too rich because you’ll quickly find the flat spot which is caused by the changeover from the enrichment from the acceleration pump the airspeed of the carb. You’ll have a difficult job to over lean it as the nature of the carb runs rich, so start at the end of the adjustment thread and wind it on as you tune it. Once you’ve got the output of all acceleration pumps the same it’s time to refit the velocity stacks and go for a little drive to get some temp into the engine and see how it runs. Back the throttle stops off if you haven’t done so already and it’ll probably have a decent enough steady idle so you can go for a run. Not wanting to scare anyone at this point, but if you’re driving the car without the air cleaner, take a fire extinguisher as an insurance policy, it’s always worth having it with you if you’re driving the car without the air cleaner on. OK go for a drive you’re earned it! Accelerate up to about 5k RPM, lift off and let it over-run as the engine drops to about 3k RPM floor it. If it accelerates away cleanly you’ve got it pretty good. If the engine stutters, coughs and dies with no power you’re not running enough fuel. You’ll get a feel for the adjustments you’re making. If you’re racing the car have a little tune on the day, it’s sensitive to temperature so those marginal gains will be useful to you. For road cars you’ll find some settings that’ll suit you for summer/winter. When you’re fully happy with the amounts it may be worth marking the volumes on you vial. For the serious racer get an air density meter and write down your volumes in a little book, It’ll pay off. The flat spot can be tuned out with time and patience. You can understand why webers are so easy to use, they’re using two carbs and we’re using six, but you’ll find that a properly set up Solex car will produce more power than with webers.

Once the engine has ran up to temperature, it’s time to set the idle mixture screws. Back the throttle stops off all the way so the throttle valves are fully shut and it’s onto the idle circuit only. Now it’s time to wind each one in and out BY HAND until it’s running as smoothly as possible at 900RPM, just as the workshop manual says. Go and have a beer, you’ve earned it!

I’m sure this isn’t the only way to do it, but I’ve found it’s worked best for me over the last three years and I hope it’ll help others. Once I’d finished my carb rebuild, we tested it on the rolling road and it made 132.7 BHP on its standard engine. I’ve since rebuilt four sets (24 carbs) in this way with good results and if you’ve ever driven a properly set up Solexed car you’ll dispel all of the bad Solex myths.

Good luck with it and feel free to PM me for any additional info.

[one-two]

That is a fantastic contribution, and ideal for road use. However, I don't think you can race competitively with anything like the standard set-up. Most of us are, I suspect, doing something quite different!

[Schläfer]

I've seen some of the rally guys replacing the mechanical pumps with pierberg electric pumps. I'm curious to know how else they are raced?

[John Straub]

You got it! I love the Solex carbs if set up right.