At this point, my Shaper is just about finished. It will be powered by a brand-new Orwick 29 on spark ignition.

A couple of days ago, I decided to run the engine in on the stand. Going through the usual drill, I mounted a 10-6 wood prop and set the engine up on the stand, complete with my trusty ignition box (anyone interested and I’ll write about it).

After around a half hour of flipping, I finally got it started.

In a word, PATHETIC.  It made so little power and ran so rough, I doubt that it would have taxied the plane. Tried the usual – different plug, different fuel, even a different prop. Still pathetic.    Since Orwicks had a reputation for being powerful engines, something was definitely wrong.

Next try, pull the head and see what’s going on inside. Looked at the head.

First surprise – no combustion chamber.    The bottom of the head was flat, as seen in figure 1. The spark plug was recessed around ¼ inch above the flat.

Second surprise – the sleeve was rotated 180 degrees. On the downstroke, the intake port was opening around 1/32 of an inch before the exhaust port.

I modified the head as shown in figure 2, rotated the sleeve to properly orient the ports, removed the thick fiber head gasket and installed a thin aluminum gasket and reassembled.

Starting it now was a snap and the engine came alive.     Turned the 10-6 wood prop at just under 11,000 RPM. The fuel was regular gasoline with 18% castor, 6% synthetic.

Except for my ETA 29, this is the most powerful 29 I’ve ever run.

Bob Z.

I'm running two Orwick 29 engines ( made by Henry Orwick, after 1950)  One on spark ignition and one on glo.  Both are very strong, and certainly equal to any modern 29.  Just remember to use lots of oil, about 25%.