Inverted 4-stroke questions

Model Airplane News - RC Airplane News | Inverted 4-stroke questions

Mr. Lee, I have been a long term reader and thank you so much for sharing your wealth of knowledge! 
    My question: I have installed a Thunder Tiger 91 4 stroke in a P-47 with the head at about 7 o’clock position. (Not quite totally inverted). So now the drain nipple on the bottom of the crankshaft  is pointing up like at the 1 oclock this going to be a problem for the bearings not being able to drain the oil out while sitting? I still plan to run a hose out the bottom of the cowling for emmissions to escape… Also, What range should I see on cylinder head temps on this motor that would be considered normal? I do have a cowling with a baffle to force all air by the cylinder & head when running and a large exit hole around the muffler to let the air out of the back of the cowl… Thank you so much!

Terry B 

Hi Terry,

The vent fitting on your engine is not exactly a drain. It is more for equalizing pressures within the crankcase, i.e., on the up stroke of the piston there is negative pressure, and on the down stroke positive which blows the oil out. The fitting being at 1 o’clock will not hurt a thing. The cylinder head temperature should be in the 320 to 360 degrees ranges. Anything over 400 degrees would be excessive. 

Clarence Lee

Updated: June 6, 2011 — 9:24 AM
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