Engine cooling

Well....... As it turns out, if you look closely at the pic, there are little holes on either side of the big oval center hole under the spinner. They are backed with nut plates. Looks like someone in this poor plane's long past put SOMETHING over that hole which has long since been lost.

So, I took Larry's very helpful Skyport engineering drawings and enlarged them on my printer enough so that the resultant size just overlapped those holes, traced it onto a 0.040/30 piece of scrap aluminum stock, and cut it out on the band saw. Screwed it in place with lock washers and now the oil temp comes off the peg in anything over about 20 deg OAT. The cabin heater works better too.

Thanks again Larry for your help. Anyone else need the template let me know and I'd be glad to mail a copy for the usual fee of $5000

Actually, it's free and I'll even pay for the stamp.

Chris

I have used some foam like from a foan cushion, cut it a little large and stuff it in the hole behind the prop and it helps.

Jack

Thanks Larry. That'll be a big help, even if for no other reason I know what hole to plug up now.

Chris

My oil temp does not come off the peg in cool weather either. I think it reads low even in the summer. I use Phillips 20 X 50, so am not concerned. A 50 weight oil could be a problem.

Dang, it's cold up here in South Dakota and when I fly my 415C, Ser# 504 with a C85-12F in it, with OAT's of less than 35 deg or so, the oil temp never comes off the peg (100 deg F). I can't get a clear answer as to whether there was ever a 'winterization kit' for these planes. I kind of doubt there were wind tunnel tests or CG simulations when the cooling holes in the front cowl were designed but I know that wind flow through it can be quite critical and if disturbed or altered might leave one or more cylinders with inadequate flow. Here's a picture. The small hole on the right of the cowl (left side in the pic) is connected to tubing that leads to the generator and mags to direct cooling air onto those accessories so I'm inclined to leave it alone. The one that's taped over has no such tubing attached and is open to the engine compartment as a whole. Taping it over made no difference in oil temp whatsoever. Temptation is to put a piece of styrofoam in the center hole above the carb intake which opens onto the base of the intake spider where the mixture from the carb is distributed to the individual pistons.

Any suggestions?

Chris