Let'sgoflying!
Touchdown! Greaser!
So I am reading on several of my other av forums about what causes ex valves to leak but did not see these recent ideas here.
I think we've all heard about valve guide wear leading to poor seating resulting in leakage, then the non-pizza borescope images - and later; low compressions.
Maybe everyone else has followed it and I missed it - but now I am reading about other possible causes or contributors;
-poor rocker arm face to valve stem geometry
-factory valves in which the stem is not 90° to the valve face (some disassemble brand new ones, and run them on a lathe or other machine to check)
-valve guides which are not drilled straight or 90° to the seat
-prussian blue test, for rocker face to stem tip contact check
-poorly designed rotator caps; when they stop working, the valve is doomed.
(I was taught the lipstick test to ensure new valves touch the seat equally around the circumference)
and, apparently that 'slide' or 'shift' seen, as a valve seats, on borescope images - may be largely 'no big deal'!
Here is a video on the topic posted by Dave Pasquale, "our" Viking mechanic hero....and apparently now he is becoming well known in Beech circles lately:
The early part goes slow. I can't remember where but you go past 10? 20? minutes of it, to the meat and potatoes. Also, I turned captioning on and went 2x speed to make this >1hr video more suited to my available free time.
Long discussion going on in BeechTalk too.
I think we've all heard about valve guide wear leading to poor seating resulting in leakage, then the non-pizza borescope images - and later; low compressions.
Maybe everyone else has followed it and I missed it - but now I am reading about other possible causes or contributors;
-poor rocker arm face to valve stem geometry
-factory valves in which the stem is not 90° to the valve face (some disassemble brand new ones, and run them on a lathe or other machine to check)
-valve guides which are not drilled straight or 90° to the seat
-prussian blue test, for rocker face to stem tip contact check
-poorly designed rotator caps; when they stop working, the valve is doomed.
(I was taught the lipstick test to ensure new valves touch the seat equally around the circumference)
and, apparently that 'slide' or 'shift' seen, as a valve seats, on borescope images - may be largely 'no big deal'!
Here is a video on the topic posted by Dave Pasquale, "our" Viking mechanic hero....and apparently now he is becoming well known in Beech circles lately:
The early part goes slow. I can't remember where but you go past 10? 20? minutes of it, to the meat and potatoes. Also, I turned captioning on and went 2x speed to make this >1hr video more suited to my available free time.
Long discussion going on in BeechTalk too.
