The Murphy Builders Site

Has anyone tried mating the Vans air intake scoop on a set of Murphy's speed cowls and the Vans air intake box. to get the proper cooling.

Murphy's fly to slow to use Van's system....

You talking this air box?

Make sure you install the alternate air inlet option!

Thanks Wayne so your better off to modify the existing cowls the way you describe, and yes will install the alternate air source.

Your choice..... Modify Murphy stuff or van's. Either way, you need more air in.

Yes, but Walter is the speed cowl "guru"! :shh: Follow his advise that he's given here many times. I hate the thing myself...

As for fiberglasss air intake box, it was on this Elite when it came into my hangar for the amphib install. The way it works, filtering both ram and heated air, if you suck in a garbage bag or something (unlike a regular carb heat / air box that gives one side filtered the other side direct) you have no alternate means of getting air to the engine. That's where the alternate air plate comes in...

This air box is also a good addition to the O-360 series engines, as the smallish air box MAM was putting in the FWF kits gets the flapper shaft pivots destroyed in less than 100 hours due to it getting sucked back and forth at full throttle. The carb can't get enough air through the filter side so it tries to suck air from the carb heat hose side and the flapper goes nuts taking the bushings out in short time.

Speed cowl, yes, of course I love them,... so sexy... But you have to know how to cool them...

And I use the Vans airbox, with no modifications to the cowl, just have to install the Vans airbox so the "snout" lines up properly with the speed cowl air inlet, pretty easy actually.

I am not sure why there would be a concern for enough air intake with the Vans design, as it is supposed to handle up to a 540 engine. With its wide diameter round style, it has a lot of intake filter area, much more than the square box style. And the intake on the cowl is the same size as for the square one. And after the air gets past the filter, it still has to squeeze into the carb air inlet that is always the same size no matter what filter you use. The engine is not dependent on ram air, and at 80 (climb) to 120 (cruise) mph, it seems to be getting all the air that it wants. My initial climb fuel flow is over 18 gph, so am quite sure it is making max power. And yes, you "should" have that alternate air source.

My wife and I did the fiberglass work to mate the Vans scoop to the Murphy speed cowl on our Elite. Don't like fiberglass work, but it went well. The curve of the Vans snout matches the curve of the speed cowl. Very surprising. Good time to make sure you have a good size opening for hot engine air to exit out of the bottom of the cowl.

I have a Superior O-360 and the carburetor is offset compared to the center-line of the engine and cowl, so the airbox needed to be angled. Not a big deal, but interesting. The rest of the airbox fabrication is well documented in the Vans instructions. It is an interesting carb heat design as pointed out by Wayne.

I now get better fuel distribution between cylinders: more even EGT and CHTs in various power settings. Not true with old (too small) traditional airbox.

Eric
Elite N645E
Rebel N112R

As long as we are discussing air boxes, is anyone installing any baffling between the front of the air box and the cowl itself? It would seem to me that any air leakage past a gap between the two would/could reduce the flow of cooling air from the top of the engine to the bottom and then out the exhaust area. Or is this not a factor?


Tim

Thanks Eric that's what I needed to know probably looks pretty good also, and this does give enough air flow out the bottom, I am only putting in an 0-320 150 HP on wheels so I should be fine. :clap: :clap:

Eric just wondering if you have any pictures of your work and maybe the finished product would sure help for me and maybe others. Thanks again.

tjhickey wrote:As long as we are discussing air boxes, is anyone installing any baffling between the front of the air box and the cowl itself? It would seem to me that any air leakage past a gap between the two would/could reduce the flow of cooling air from the top of the engine to the bottom and then out the exhaust area. Or is this not a factor?


Tim

Yes there has to be a boot made to seal the intake air to the air box Vans forums have good directions.

I have been hunting through some old photos looking for some guidance on improving the cooling with my "speed cowl". I found this one that gives a pretty good look at Walter's outlet and why it works so well.... its huge. So I guess I'll be back at the fiberglass soon. Pretty nice photo...eh?

John

And to think that was July 13, 2012(just checked my logbook), and there was still ice on the lake. The previous year, 2011, the ice didn't go off until Aug. And this year the lake has been open since March!!

BTW, the trout are getting really huge now in this lake. :shh: (did you hear that, Ray?) I guess a couple warm years makes for more food.

Here are a couple of small pics, but more pics on my DropBox site for details on the airbox itself and some showing the "fun" fiberglass work. Make sure to safety those airbox plate nuts so they don't get sucked up into the engine. And consider Wayne's alternate air/bypass.

https://www.dropbox.com/sh/8b0tp0oxzr17 ... kMnsa?dl=0

Eric