How much clearance, James to engine?

[bret]

Working on the baffles and plenum design and there is not much room with the angle valve 360 and James cowl on this 7a. I have installed the long cowl all the way out, (actually had to add 1/8" on R. side) with a 3" spacer for the HZ CS prop. How much vertical movement should I expect there to be at the valve covers during start up and shut down?

[BillL]

Be very careful about adding length on the R/S. The engine is twisted to the right and the prop is closer to that side at full pitch. 3/8" is good from cowl to prop. Lately, RVBuilder2002 says 1/4" is ok. Your prop, your choice, none of this comes with a warranty. Also, hanging a metal prop at 3" is limiting on your aerobatics. Standard SJ spacer is 2.25".

Rocking clearance about the mass center (some magic number below the crank centerline, but angling up to the center of the prop flange, is .400-.500" from what I can find.Far right/left forward corners of the engine are the most critical. Some report 3/8 with no touching. DanH has his plenum structure very close and says it touches, but no hard interference (sometimes?). I don't remember his static clearance. Mine is .4" but will be checking it with clay in Phase I.

Your research may vary. YRMV

[bret]

Ok, Cool! I should be good then, whew, I had the engine bolted up and prop shaft-spinner centering the cowl, there just so happened to be even spacing on the cowl to front cylinders, I can fit my finger in between the two, the way the nose tapers in, I'm glad I went with the 3" its just that with the 3" spacer, I was just shy for material on the lower R side cowl, just added a sliver to make the gap even.