As I see it there are too possible choices.
You can use two evap cores like Tracy does or you
can use a one or two inch thick core of a wide selection of sizes.

In the first case the core total core volume is about 700 cubic inches

give or take a few.

In the second case it can be almost anything you want it to be.

Paul, I think that 700 cu.in. of radiator in an rv-4 cowl is a bit
optimistic. I just recieved the exact same rad that Chuck Dunlap has(I

beleive). Give me two weeks and I'll send pictures of the
installation. Can Chuck give any information on how his cooling works?

I know that you recommended just letting the air dump out of the
bottom of my cowl, but I think that that is lacking in elegance(a
serious engineering consideration). I've got what I think is a good
cowl flap mechanism setup that, like I say, I'll share in a couple of
weeks.

Brian Trubee
Making progress after all these years

Well Tracy does not think so :) If you use evap core it is probably not
optimistic :) You have a point though. You can always improve the
cooling by putting more volume in your heat exchangers. If two evap
cores don't quite cut it put in three :)

All joking aside I think Chuck's core will work fine with a little
aerodynamic tweaking.

Chuck, what is the latest on your cooling experience?

Paul Lamar

All this summer my water temps have been creeping higher, driving me
crazy trying to figure out what was going on. Tried recalibrating and
changing water temp probe, adding more heat shields on the exhaust, cut
out shark gills on the side on the cowl to reduce in cowl pressure,
nothing helped. Temps have gone above 230 a few times on climb-out where
they used to rarely go above 210. Never did lose any coolant. I finally
removed the radiator to try and improve the inlet duct shape and
rad-to-cowl seal, and I found the inlet side of the rad tubes were
mostly clogged up with partly hard calcium? deposits and partly the
dreaded silicone "worms" left over from sealing water pump and
thermostat housing. I guess I still haven't learned to stay away from
that stuff, even after you may recall I had some find its way into an
oiling jet in the e-shaft which eventually cooked one rotor. I can only
figure the calcium deposits might have come from the jackets of the used
housing I used, I have always used only distilled water.
I got most of the clog out and I will try it again soon, maybe this
weekend.
I also made  a filter out of coarse Stainless screen that will be easier
to inspect and should catch most stuff before it gets to the rad.
My rad is a custom made Griffin, the core is 10.5 x 20.5 x 2.5 for a
total core volume of 540 cu in.
If the cooling is still not back to where it was, I will have another
rad made, a couple of inches bigger.

Chuck Dunlap
RV6 13B 4 years and 400 hours

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