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[Ollie]

Anyone got any experience balancing twin carbs?

I'm assuming it's pretty much just a case of shoving the flow meter into each one to check they're pulling the same amount of air through and then using my colour-tune in each cylinder to check the mixture is right?

Question is, how do I decide or find out what the right flow is?

[Mizka]

What kind of carbs do you have? It's important to get butterflies syncronized. But don't worry for vacuum meters, you'll only need to get them open at the same time and u need only sharp eyes. I have 40 mm DCOE Webers and they are easy. There are small holes (two in each venturi) covered with short thread screws. Every venturi has it's own of course. You have to move the butterfly axle to see the movement of the flaps and compare it to others. Find the first one that opens and adjust the others after that.

When you are done that then you should start to worry about the mixtures on each cylinder. At this point i'll hope that you have even somekind of lambda sond or such in your car or at the present. And once again, start at the bottom. Close all the mixture screws but gently, you don't want to drill them in. Now open every mixture screw about 360 deg. Start the car and warm it up. Set up the idle that the engine will run about 2500 rpm. Wait.

Stall the engine and check the fuel level from the choke chamber. Adjust at manufacture limits. Start the engine again.

Now the engine runs on it's own but not nicely. Start to adjust the 1. cyl mixture screw about 1/4 turn open. Wait. If that made even a slight improvement that's fine. Now you'll do the same to the others but remember that what ever you do, wait a second before making your next move. Only small adjustements are necessary and only each cylinder at the time. Go through every venturi as I said. Now check what the CO and lambda levels are. Dont't mind the HC levels if you're having a high lift cam. Adjust more open if it's too lean. Now set the idle where you want it. Don't go under 900 rpm, or you'll end up with coal sticks instead of spark plugs.

Go for a short test drive. Set the ignition after this and check mixture once again and you are good to go!

Well this is it for tonight, let us know the outcome. I'll hope u understand, my english is quite bad. But hey, u'll try to speak finnish

[Ollie]

They're DCNF's, so a bit different to the DCOE's. I'm not actually sure they have seperate controls for the butterflys in each venturi but I'll have a look, I've got a weber carb book which covers them. Thanks for the info.

I doubt I'll be fitting them for a while though, they're still sitting on a table waiting for me to find the time to rebuild them, never mind fit them.

[Mizka]

Ok. If the carbs have been without use for long time, you should replace all the gaskets before installing them again. And it would be wise to remove and keep the jets in a small gasoline or thinner containing bottle during the storage. Helps against corrode and oxidize. This includes all the jets, not just main jets.

BTW they are useless in the table. Just put them back to business