The International Cessna^® 170 Association

Valve springs can be weak and fail to excersize proper valve action, especially with a cold engine. But the springs are tested independently from the installed condition. (I have a number of springs which have failed the test in a bag with red tags. I also have some used spring which pass the test. I have no idea why I'm keeping the failed springs.)

I have a lot of old and worn-out parts in my hangar on my special "Shelf of Shame". I keep them because each one reminds me of a problem solved and something new and shiny installed.

Regarding valve height, .015 change is insignificant to the spring operation. The valve stem tip sitting higher might cause insufficient dry tappet clearance, in which case you'd have to replace the pushrods with shorter ones. Or slightly grind down the ones you have.

Failed springs make good vibration isolators for generators, etc. You can always find good use for failed parts. A good spring compressor always works to check specs.

John

Just to let you guys know I understand who I am and yes, I might be in a analysis paralysis mode. (my Wife loves to throw that term at me) I'm the type guy that will not go into something unless I have ample information. It is something my Mechanical Engineering background and my work dealing with perfection for the last 42 years on a daily basis doing race engines has created. I know what I saw when the cylinder was pulled off and it is something that is just on my mind. You guys had better be glad "I know nothing" (Like Schultz) about electronics. If I did we would be discussing my panel.
LOL!
Thanks
Adger

n3833v wrote:Failed springs make good vibration isolators for generators, etc. You can always find good use for failed parts. A good spring compressor always works to check specs.

John

Whooo-HOOO! GOOD one, John!

I have 8 sets of generator vibration isolators listed in The TradeMart. Cheap.

Sixracer wrote:Just to let you guys know I understand who I am and yes, I might be in a analysis paralysis mode. (my Wife loves to throw that term at me) I'm the type guy that will not go into something unless I have ample information. It is something my Mechanical Engineering background and my work dealing with perfection for the last 42 years on a daily basis doing race engines has created. I know what I saw when the cylinder was pulled off and it is something that is just on my mind. You guys had better be glad "I know nothing" (Like Schultz) about electronics. If I did we would be discussing my panel.
LOL!
Thanks
Adger

Adger, you might want to call Ly-Con in Visalia, CA. They are an engine overhaul shop who also build aviation race engines of all kinds including the O-200 used in Formula 1 racers. The O-200 uses the same cylinders as the O-300. Maybe they would be willing to share some knowledge.

I know a little about 6 cylinder engines and RPM, too.
Here I am leaving the line @ 7,000 RPM In my National Record holding SuperStock Camaro.
http://www.youtube.com/watch?v=eZPI6eCN8pE
My V-6 is tough on valve springs. Shifting @ 9400-9600 and crossing the finish line @ over 9600 with valve lifts near .900 of an inch. I have some very elaborate spring preparation and testing procedures to make the best I can buy last a while.
Ly con is where I found the shims.
It is a shame so many of these aircraft engine rebuild facilities have the A&P's and pilots believing that all this rebuilding is "Black Magic"
It is only having the specs and following the correct procedures. I'm beginning to think there is a climate of protectionism in the aircraft world. Those that really know don't want anyone else knowing. Yes, they have the Feds on their side, too.
I'm not trying to make a race car engine out of this O-300, just check a few things.
It would be nice to know if I'm a victim of someone that did work improperly and signed it off as done properly.
Adger Smith