Hi all

is the vacuum port on the 4100 deemed to be "ported" or not?

stuey

UK

If you are referring to the threaded port under the right side of the primary fuel bowl, it is a staged or ported vacuum source. Tracing that port should find a hole located above the throttle blades when the throttle is in the idle position.

Lorena, Texas (South of Waco)

Thanks for the reply Mr. Eaton

Yes that is the port I was referring to.The tiny hole on this carb , with throttle blades closed, is inline with/covered by the edge of the throttle blades. I'm thinking any over adjustment of the hot engine idle screw will expose the hole and therefore increase initial timing.

Can hot engine idle be achieved by using the little grub screw acting on the secondaries?

Should i be looking at reangling the drilling?

Any insight would be greatly appreciated.

Many thanks.

stuey

In the event the staged vacuum hole becomes exposed due to the primary throttle blades being opened too far, then the secondary blades can be opened up in which to close the primary blades. Another option is to drill a small ‘air’ bleed hole in each primary throttle blade which will also allow the primary throttle to be further closed assuming they are open too much. The hole drilling trick is commonly done on the Holley carbs to reduce the amount of fuel transition slot that can be overly exposed by too much throttle blade opening. Putting too small a carb on an engine or going with a much larger camshaft are just two of the reasons a carb may have too much primary throttle opening.

Lorena, Texas (South of Waco)

Thanks

i feel like i've gone back to school

cheers

stuey