[urq] Too much Crankcase ventalation?

Ben Swann benswann at comcast.net
Tue Sep 4 16:22:47 EDT 2007

I am finally able to drive the Ur Quattro that has the new engine with
Megasquirt - Yeah!.  Engine is balanced MC-1 with NF head.  I am now tuning
it, so it will get better and better, but starting way rich, and trying to
figure creative ways to tune since I don't have ready access to a dyno.  I'll
probably need to have someone drive as I make changes to the VE tables, etc..


Anyway, after my first extended tuning session and the engine was on the warm
side, I noticed a nasty squeal almost like a loose belt when the engine was
idling.  I feared the worst as it seemed to be coming from the head and
sounded a little like a metal machining noise, but went away when I gunned the
engine.  Oil level was good - still on the Havalone break-in crap.


I pulled the oil cap and the noise went away with a release of some serious
vacuum.  I repeated this experiment only to conclude that there is so much
vacuum on the head at idle, that it is probably evacuating the cam bearing or
something to that effect.  If I left the cap loose, the noise did not come
back, each time I tightened the oil cap, the noise cam back in a few seconds.
I have the UrQ PVC hose setup, but so much is removed of the CIS stuff, there
is fairly much a direct draw into the Intake manifold and the engine is
pulling a good 18-20 lbs of vacuum at idle.


So just seeing if there is any solution to this.  I would expect I should have
some ventilation in the cam area, but this is too much.  Ideas?



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