O-360 sticking valve update

Hello all. I know it's been awhile since I updated, but progress has been
slow. Here's where we're at:

Last weekend:
- Pulled valve covers, rockers, pushrods, exhaust.
- Pushed on valves and were unable to feel any sticking like there was the last time
we definately had sticking valves. Decided to get the tool to compress the valve
springs and build a jig to do the "wobble test." (SB388C)

This weekend:
- Did "wobble test" after using tool to remove valve springs. Front guides (#1, #2)
in the middle of the "wobble range." Rear guides (#3, #4) at the top end of
acceptable (0.030 wiggle measured 2.5" away from guide). When the valve were almost
completely closed, the wobble test showed wobble towards the *tight* end of the range.
All valve seats, stems looked and felt good when spun in-place.
- Noticed some buildup of lead on exhaust valve stem as viewed from inside the exhaust
port. Nothing that seemed unusual.
- Could feel extremely subtle resistance to sliding of a valve or two in specific
orientations (both rotation and excursion). Stress the "extremely subtle" part...
couldn't feel it unless you were very careful and methodical to find it.
- For comparison, removed intake valve springs and intake runners. Noticed some
buildup of carbon on intake. Enough to change the tone of the *ding* when manually
closing the valve.
- Wobble on exhaust valve was a bit more than intake, but nothing too out of line.
- Pushing the valve almost out of the guide and examining with a light revealed very
clean-looking guides. No detectible wear or buildups.

Notes of possibly interest:
- Some of the valve spring end caps showed little indication of valve rotation
compared to others. Some had nice, shiny marks all the way around, and some had brown
oilgunk stains on them showing where the springs lived.
- All the crank rotation we did while checking stuff inflated the lifters so getting
the rockers on was a @#$^!!#$@@ PITA!


Conclusions:
- After my partner, mechanic, and I debated on everything for a good long while, we
had a tough time concluding that there was anything heinously wrong with the valve
train. We cleaned all valve stems and guides with generation applications of MEK,
Scotch-brite, and scraping for the lead salts and started putting it back together.
Thoughts are basically that marginal sloppy guides do not *inherently* cause sticking
valves, but they do promote additional buildup that can. We removed a lot of the
buildup. Short of pulling all the jugs off and having new guides put in, it seemed
like a sane choice.

- Operation procedure could be inducing the valve sticking at takeoff. I generally do
not like to get the CHT's over 250 before taking off since I don't want things to cook
too much on the ground. I usually want at least 200 before taking off, however.
Within a minute of takeoff, they're usually reading 350. Perhaps the shock heating
heats the low-mass exhaust valves so fast that they expand in the
still-heating-and-expanding guides and causes a slight sticking. Once everything is
up to temperature a minute or so after takeoff, everything slides as it's supposed to.


Thoughts? Comments?
-Cory


--

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