If anything has happened in the valve train, you should verify that the cam
lobe and lifter face are still good. The broken valve spring might be the
result of cam wear or something entirely unrelated could have happened and
the improper function of the valve train could have damaged the lifter.

The valve train is very delicate and has some of the highest stresses in the
engine. Any difficulty should result in a complete check from the cam
through to the valve seat.

I know of one case where a broken valve stem was simple replaced. The
engine later lost power on take off and three people died.
--
Roger Long


John Clonts wrote in message
om...
The IO-520 in my Cessna 210 is running rough. It seems to run smooth
at 1000 rpm but the roughness appears above about 1400. One cylinder
is “cold” and apparently not producing any power. I
pulled the rocker cover and found that the intake valve spring was
broken. My mechanic and I replaced it yesterday. But the cylinder is
still not producing. The compression is good (74/80). The spark
plugs are good. He’s going to check the flow through the fuel
injector later today.

Any more ideas? What should we do next?

Thanks!
John Clonts
Temple, Texas
N7NZ