Twin Weber Vacume Lines

[tils101]

Hey guys just wondering how you've run vacume lines using twin dcoe's on a redline manifold. Is it ok to tee into the one connection on the manifold for brake booster, dizzy and rocker cover? Or do I have to tap a new one into the manifolds flange?

[altezzaclub]

I went to the trouble to tap all 4 and T-junction them once, but I don't think it was worth it.

 

The brake and dizzy lines don't really flow any air, they suck against a diaphram and only bleed in a tiny amount when you brake.

 

If you have the PCV set up as factory, the rocker cover vent will flow air from the crankcase under acceleration, which in theory will lean out one cylinder slightly. If you think about how many litres/sec of air is getting sucked in down that carb throat, and how little the rocker vent adds, it may not even be notcieable.. 6000rpm=3000'inlets' on one cyl of 425cc, so 0.425X3000/60L/sec or 225L/sec of fuel and air... Seeing the PCV is only open at low inlet vacuum there is not much suck at all pulling air in from the rocker cover and around the PCV valve itself. If you suck on an open PCV valve you'll get a litre or two a second.

 

If you're keen, put the brake into one manifold and the PCV into the other. See if you can find one cyl running leaner than the others.