Weber, Valve cover questions

[darrellhuth]

I removed the Webers / intake manifold a few days ago to clean them up and check them as they did not seem to be working right. The car was idling too high ( around 1400 rpm ) ...I went to turn down the idle stops a bit and found they are missing? Don't know why someone would leave them off. I checked the throttle shafts / chokes and all seems ok, idle mixture screws are all around 1 1/2 turns out. I took them off mainly to clean them up as they were quite grungy. Do these carbs require constant cleaning with use to keep them from looking that way?  Now to put them back on and see if I can get them to behave on idle.

One of the spares I got with the car was a nice cast valve cover. it has no oil cap? I am assuming it is to be used with a dry sump setup?

Thanks, Darrell / California

[Dave Eastwood (Gadgetman) - Club Chairman]

Sorry can't help with the Webers, my twin carb days were with Delorto's, simliar but different in the details  

On the valve cover front, you may be right; many tuners/builders spec a scavenge pump/stage sufficiently powerful to allow the engine to run at less than atmospheric pressure inside the crankcase. (sometime refered to as running under vacuum, though that's a bit of an exaggeration!)

While I've not direct experience of a crossflow set up like this, the other engines I've come across designed to run in this fashion have all had the oil filler cap opening, dip stick opening and numerous breather openings sealed to atmosphere. Any blow by and combustion gasses are then drawn out with the "used" oil by the scavenge stage of the pump before being de-aerated in the DS tank. The DS tank then has it's own breather, (and catch tank).

As you can see though, for the system to work, you must have the right DS pump and tank. It's not just a case of blanking off the engine openings.  

[Hammy]

There is only one idle speed screw that adjusts both carbs !  If the screw is missing then you either have an air leak, cable to tight,  or the butterfly's need re- cantering if you see getting 1400 rpm . it shouldnt run without the idle screw !