I am running a 140L in a Caprice with a 16-11 APC prop. The motor does not seem to like this combo. It starts to heat up in sustain vertical and such. There is plent of air blowing right on the cylinder fins and I have LOTS of exhaust area where the pipe exits. Would it be beneficial to open the cheek cowl and direct some air of the crankcase area? The head has had some work done to it by Mike McCormick out of NC. It idles forever and runs like a champ. I have not tached it as of yet, but it is turning quite a bit harder than the 120 NC I have with the same setup. The ports in the head have been cleaned up and had the sharp edges removed and polished. Would polishing the inside of the plenum around the rotor disc help any with more performance, assuming the overheating is simply due to inadequate airflow? We used to build a few mild chrysler drag engines, and its in the blood to tweak a bit more out of it!

thanks

jeff

My L didn't seem to like the 16x11 either, I think it is too light a load. I am going to try something like a 17x8. If you want it for pattern, maybe a 16x12 or 16x11W (If they make those sizes) might help. I am not sure what sort of 17 inch prop would be suitable for pattern, check your instructions.

140L's yield great performance when operating in the low to mid 8K rpm range. Given that variables such as air density, nitro level, airframe drag and airframe weight will be the guiding force that determines what works best for you. Below are a few APC sizes you may want to consider for pattern application that I have had good results with.

Size
15x12
15.5x12
15.5x11.5W
15.5x12W
16x12
16.5x12N
17x10N

Glen
http://www.geocities.com/rcprecision/pah.html

What is the 'N' for on APC props? I was going to use a 17x8, but that might over rev. it. I'll use it for 3D.

that "N" associated with a prop generally means "narrow". just as "w" means "wide".

Ooops. that is kinda obvious. What effect does the 'W' and the 'N' have? This might look off subject, but I am still trying to find the right prop.