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whats the main adjustment screw supposed to be on a 235 with a rochestor. I need a starting point

mightymousem6,

The typical adjustment for the idle mixture screw is approximately 1 1/2 turns out from fully seated.

Stuart

My recent search turned up the opinion by several that the "tried and true" 1 1/2 turns out should actually be "3 turns out" with modern fuel. I don't have enough experience to comment, but food for thought.

My Auto Restorer showed up today. In an article by Milt Webb MiltTheInstructor.com, he is tuning up a 27 Hupmobile. He discusses opening the idle mixture screw until the engine stumbles (over-rich), then closing the screw in until it runs smoothly again, then in further until the RPMs drop off (lean point). Final adjustment is half way between these two points (generally). This assumes everything else is tuned, ie: timing, advance, plug gap, point gap, etc. and should be done on a warmed up engine.

Sounds stupid, I know, but I never really thought of this. Makes sense.

-Michael

I always start with it screwed out 2-3 turns. Turn it in slowly till it starts to slow down. Then back it out just enough to bring it back to speed. This is similar to Milt's system & was used for many years till they started with emission controls.

1 1/2 turn off the seat always works good for me.
SlickT