gofastpilot

I recently put into service 2 freshened 1994 HP 500's. The motors were rebuilt with new rings,bearings, severe duty valves,new valve springs and new teflon valve seals.
My question is regarding a small amount of blow by coming out of the valve cover breather hoses which exit into the spark arrester. The teflon valve seals were installed per a tech article from PB mag where as the tech guy stated that when installing the exhaust valve seals you should remove the tension spring that squeezes the seal to the valve stem thus allowing I believe better oiling for the guide/stem. Could the blow by be caused from the loose fitting valve stem seal? The intake valves are using full tension on the seals........gofast

paradigm shift

Blow by is caused from piston rings not sealing. The oil seals on valves will not cause it.

gofastpilot

Just discovered # 3 cylinder has no compression all the rest have normal pressure @ 150 psi. Pullin the motor tomorrow.............gofastpilot

paradigm shift

Maybe just a head gasket. Hope it did not hurt to many parts. My first post assumed it was running on all 8 cylinders.

gofastpilot

Pull the heads today found 4 melted pistons. The #3 cyl. that didn't have compression had the most damage.Amazingly the cylinders are fine and there was some aluminum metal transfer on the heads. The problem was that I made a fatal mistake when I set the ignition timing. The harmonic damper has 2 timing marks. One is TDC and the other is 34 deg. BTDC. I mistaking took the 34 deg mark as the TDC mark, the rest is history.I may be 50 years old but I'm sure learning alot............Gofastpilot

Turbojack

Did you have the timing off on both motors?

paradigm shift

Well at least you do know why and I bet it will not happen again. I learn every day and some of my boat motor learning has been expensive just ask my wife. On second thought don't ask better left as is.

gofastpilot

turbojack.....no I didnt screw up the timing on the other engine because I timed it off of the proper timing mark. In my pursuit to get the engines running I neglected to accent the timing marks with a light colored paint which would have clearly shown the differance in the 2 marks.My mistake again...........gofastpilot

Offshore Addiction

boy,I'll bet that motor made a ton of power for a few minutes!