A little stumble if you stab the pedal - Webers

[EarlyPorsche]

I get a little stumble if you stab the throttle when the engine is coldish...I never really had this before but I have a feeling its a cleaning issue. Should I remove the six jets that thread into the side of the carbs and clean them? Can I also try spraying carburetor cleaner into the webers and work them with the engine running? I think it just needs a little spray out and an italian tune up.

[Steve@Rennsport]

When the engine is cold, its mixture requirements are different so one needs to review jetting, idle mixture settings, accelerator pump volumes, etc.

[Joe Bob]

Cold, carbed engines are like pissy girlfriends w/o coffee in the morning.....

[EarlyPorsche]

I know. But in the past 5 years its never done this.

[1QuickS]

It may be a cleaning issue as you think, read my comments from this post regarding fuel injection quantities, the lack of fuel delivery would cause a stumble:

Weber Injection Quantity

You might want to try this test: Start the engine and use the cross bar to run the throttles. While at idle give the bar a twist to rev the engine, if the engine hesitates then give it a second twist in quick succession to the first (like you would at a red light trying to impress your friends on a Saturday night, years ago). If the second of third rev produces an even rise in RPMs (a responsively reving engine) then the squirter nozzle bolt(s) may not be sealing well and thereby allowing the shot of gas to drain back into the fuel bowl. After driving a bit they may settle out and work a bit better with the vibration of the running engine.

Paul Abbott
Performance Oriented