I have just had the Solex carbs on my 1968 Rallye 1.3 totally rebuilt.
The rebuilder assures me that he has set up the idle mixture screws on his test bench ready to run.
But I am having trouble balancing the carbs now on the car.
(Car now starts instantly and revs wonderfully since the rebuild, but is currently very rough and "lumpy" at low speed).
Is there a trick to this balancing? I have been adjusting the balance screw between the cars then the idle speed screw next to it. But after several attempts I am not getting the result I would like.
Is it necessary to have this mercury tube thingy as stated in the Lancia workshop manual, or is there a easy way round this?
Any help / tips most appreciated.
Mike.
Solex C35 PHH7 carbs
-
alan cooper
Re: Solex C35 PHH7 carbs
I always found using a gunsons colourtune was handy as it helped to get an even mixture across all 4 cylinders
-
Paul de Raymond Leclercq
Re: Solex C35 PHH7 carbs
The principle problem with this is the combination of getting the individual mixtures right whilst maintaining the balance between the two units.
I would start by srewing each mixture screw full in and then out one turn. Try to set the balance screw so that all butterflies are shut when the throttle is closed.
Remove plug leads 1 and 2. Start the engine (you will need to adjust the throttle stop screw as the engine will now be running on two cylinders - take care to avoid electric shock from the removed leads). With the engine running on 3 & 4, optimise the mixturte screws to get the fastest idle. Now repeat the performance for cylinders 1 & 2 (i.e. removing 3 & 4 plug leads).
Now back off the throttle stop screw, reconnect leads 3 & 4 and re-start the engine. Set the idle to about 1000 rpm and adjust the balance screw for the slowest idle (which should mean that both butterflies are closed - or in fact close to it!). If the carb balance is correct, the engine should respond promptly to a "blip" and more importantly slow down very quickly; if it does not, this means that the balance screw is incorrectly set. Adjust as necessary!
Paul
I would start by srewing each mixture screw full in and then out one turn. Try to set the balance screw so that all butterflies are shut when the throttle is closed.
Remove plug leads 1 and 2. Start the engine (you will need to adjust the throttle stop screw as the engine will now be running on two cylinders - take care to avoid electric shock from the removed leads). With the engine running on 3 & 4, optimise the mixturte screws to get the fastest idle. Now repeat the performance for cylinders 1 & 2 (i.e. removing 3 & 4 plug leads).
Now back off the throttle stop screw, reconnect leads 3 & 4 and re-start the engine. Set the idle to about 1000 rpm and adjust the balance screw for the slowest idle (which should mean that both butterflies are closed - or in fact close to it!). If the carb balance is correct, the engine should respond promptly to a "blip" and more importantly slow down very quickly; if it does not, this means that the balance screw is incorrectly set. Adjust as necessary!
Paul
-
Randy Adams
Re: Solex C35 PHH7 carbs
Paul's suggested method is probably the best. But I had a quick and dirty method when I owned Fulvias which worked just fine.
Adjust the idle mixtures BEFORE the balance.
For idle mixture, disconnect the throttle linkage. Then, one cylinder at a time, turn the screws in tiny increments. Walk to the back of the car after each tiny increment to listen to the exhaust. When you start to hear "splashy misfire" or popping (too rich), start to turn the screw back in until the engine starts to slow down (too lean). Then back it out again until just out of the point where it had started to slow down the engine. Do this for each of the four idle mixtures and you should have a pretty decent-running engine.
For balance, reconnect the throttle linkage (just in case it changes things when it's connected). You will find that if you turn the balance screw too far in either direction, the engine will start to run faster but will also rock because two cylinders are doing more than the other two. Turn the balance screw until you find the mid-point between these two points where the engine starts to speed up, or simply find the point when the engine speed is at its lowest.
Then set the idle speed screw.
If the car stumbles when you open the throttle from idle, you probably need to adjust the accelerator pumps. I never figured out a way to do that without pulling the carbs off. Perhaps Paul has a trick.
Adjust the idle mixtures BEFORE the balance.
For idle mixture, disconnect the throttle linkage. Then, one cylinder at a time, turn the screws in tiny increments. Walk to the back of the car after each tiny increment to listen to the exhaust. When you start to hear "splashy misfire" or popping (too rich), start to turn the screw back in until the engine starts to slow down (too lean). Then back it out again until just out of the point where it had started to slow down the engine. Do this for each of the four idle mixtures and you should have a pretty decent-running engine.
For balance, reconnect the throttle linkage (just in case it changes things when it's connected). You will find that if you turn the balance screw too far in either direction, the engine will start to run faster but will also rock because two cylinders are doing more than the other two. Turn the balance screw until you find the mid-point between these two points where the engine starts to speed up, or simply find the point when the engine speed is at its lowest.
Then set the idle speed screw.
If the car stumbles when you open the throttle from idle, you probably need to adjust the accelerator pumps. I never figured out a way to do that without pulling the carbs off. Perhaps Paul has a trick.
-
Huib Geurink
Re: Solex C35 PHH7 carbs
A word of caution on the method of adjusting the balance screw to slowest running. This is only correct if the idle screw is backed off till it no longer affects the idle. Theoretically all butterfly valves should also have the same wear. Since this is hardly ever the case, we accept uneven wear as a fact of life.
I always check with a CO2 meter after adjusting the carbs, just to double check nothing is way out of range. The meter shows the average of all 4 cilinders. If it indicates 4%, two may be at 8% and 2 at 0%.
There are several methods to check if the setting of the mixture screw is equal for all 4. One method is the colour tune as mentioned by Alan which I have unfortunately not tried myself. Another interesting way is to take a hair from a steel brush and bend it 90 degrees in the centre. You can then hang it in the idle jets one by one. The drop in rpm (use an electronic rpm meter) should be exactly the same for all 4.
I always check with a CO2 meter after adjusting the carbs, just to double check nothing is way out of range. The meter shows the average of all 4 cilinders. If it indicates 4%, two may be at 8% and 2 at 0%.
There are several methods to check if the setting of the mixture screw is equal for all 4. One method is the colour tune as mentioned by Alan which I have unfortunately not tried myself. Another interesting way is to take a hair from a steel brush and bend it 90 degrees in the centre. You can then hang it in the idle jets one by one. The drop in rpm (use an electronic rpm meter) should be exactly the same for all 4.