Reply to "Weber tuning frustration"

This was answering MarlinJacks question about the vacuum plumbing.

One MY CAR, each runner is plumbed to a common plenum. A vacuum plenum. This is how I did it. Other variations are possible.

You can't tune each cylinder for vacuum. Not practically anyway. You use the sync tool to balance (as closely as you can) the flow at idle.

Nate mentioned fuel pressure also. If it means anything to anyone, the factory Cobra "Team" cars running Webers used no fuel pressure regulator.

They were plumbed to a fuel plenum directly running from the fuel pump at 7 psi. I don't know if they were using the current glass ball valves liked used now. PROBABLY not but some of that is proprietary information that has been lost over the years.


The glass ball valves are also referred to as "the high pressure valves". They will let you run higher pressure safely and are needed to stop the carbs from flooding the intake when you shut the engine off and it is hot, peculating the fuel and overcoming the ability of the float to close the valves.

The heat tends to boil the fuel out of the bowls and it floods directly into the intake manifold.

If you were to try to start the car under that condition you would create a flaming volcano. Ask me how I know? Wink

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