tonight was engine check out time for me on my OS 91Surpass thats mounted in my Hangar-9 P-40.
the usual engine mount bolts,one was slightly loose now tight.
clean and inspect engine area.
check fueler for proper operation, good to go.
fuel lines for wear and potential leaks, looking good there.

and last but not least the rockers,the engine was new when it went into the plane and passed the adjustment test last time I opened it up but was on the loose end of the spectrum, since the engine was nice and cold and the house was quiet I went for it.
flipped the plane over and after wiping the engine down I unscrewed the valve cover engine looks good nice and oily makes me happy
after finding the neutral point where both valves were closed OS engines have a mark on the thrust plate I pulled out the OS valve adjustment kit and checked the gap.
well what do you know a little sloppy on my clearances over.014 the thickness of both feeler gauges put together a .004 and .010 this is over the recomended clearance.

FYI the engine will run with this gap mine was running, but might not have full power or rpm's with a little slop in the rockers, I started to notice a small drop in the RPM's and smoothness of this engine last time I flew it so I had a feeling the rockers needed looking at.

so time for a adjustment, this is a fairly easy job but I will go over it for the new 4strokers out there to eliminate the mystery around this task.

in the adjustment kit which includes instructions for doing this job if you lost your booklet that comes with the engine, there is a small wrench for the lock nut its about 4mm or so and a allen key to fit in the tappet adjustment screw, loosen the lock nut just a little and slide the smaller gauge between the rocker and the top of the valvethen with a light touch tighten the screw so it snugs down on the gauge then back it off so it slides freely, and holding the allen key tighten the lock nut.

then check the gap with the thicker gauge I go with tight for this gauge, flip the prop at least 2-3 revolutions and recheck the gap, if it checks out, repeat on the other one, and its done.

this is the one bugaboo with 4strokes and it really isn't that big of a deal,it can affect the quality of the engines performance but a once a ayear check is all that needs to be done.

I just got a new set of electric retracts,and struts, for this plane so now its ready for our new field, hope this clears up any questions about this little job, figured since I was doing it I might as well take some pics to post.