Denny wrote:
: Cory,
: 26" at 3500 seems a tad low.. Maybe others can chime in on this...
: Cam problems can result in low manifold pressure, so the plot
: thickens...

I don't remember the altimeter setting that night, but it was pretty clear
that day. I'd think it was about 30"... at 1"/1000', that'd be 26.5" theoretical max.
The MP is measured at the intake port on #3 cylinder... losing 1/2" through the
induction system is normal AIUI.

: Also in case I am misreading, static RPM check R to L is done at full
: throttle, not at 1800, or whatever you normally use for mag drop...
: And, it will verify that the impulse pin is releasing properly if they
: are similar...
Never done a full-throttle mag check with anything in particular I was search
for other than max RPM. What would a full-throttle mag drop tell you? I don't know
of anywhere the allowable spec for that is given. The POH specifies at runup RPM, and
the TCDS specifies min/max RPM for static... but that's for both mags and mixture
leanded for DA.

: Seems like you have a good grasp on engines so I don't want to keep
: throwing out picky stuff... But, once you have the cowl off I would
: still verify that the butterfly is not loose on the shaft and that it
: opens fully...

Will do once I get the cowling off.

: You don't happen to have a Precise Flight vacuum system, do you?
: grasping at straws A fine puzzle we have here... Looks like
: measuring the cam is next...

I was thinking measuring the friction on the valves is probably next. With
the covers off the cam measurement may come in. I've talked with my mechanic and he's
got a jig and dial indicator rigged up to measure it. Too bad I *ALSO* need to fix
the ring gear. I won't be able to spin it up fast to get good lifter inflation.
Maybe I can hand-turn it slow enough to keep no inflation?

Thanks
-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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