<VV> Re: VirtualVairs Digest, Vol 31, Issue 7

[Roger Gault]

Tony,
I wondered about the logs heating the heads too.  In particular, I wondered
if that was the reason the left side thermistor reads higher (under the
log).  So, I insulated the area between the logs and the heads with multiple
layers of aluminum foil to block any radiation.  I was shocked to find that
I couldn't see any difference in the thermistor reading (actually, a
thermocouple mounted on a bolt in that position).

I still think the logs should heat the heads, since they're probably running
somewhere above 1000F at highway speeds, but I don't know how to explain
away my experimental results.

I haven't run any heat transfer calculations (hated that class).  Maybe the
air blast cools the top surface of the logs enough that the amount of heat
radiated is swamped by the heat coming from the combustion chambers and
exhaust ports in the head.  Curious.

Roger

----- Original Message ----- 
From: "Tony Underwood" <tonyu at roava.net>
To: <virtualvairs at corvair.org>
Cc: <virtualvairs-request at corvair.org>
Sent: Thursday, August 02, 2007 10:21 PM
Subject: Re: <VV> Re: VirtualVairs Digest, Vol 31, Issue 7


> At 10:24 AM 8/2/2007, ssmyers at adelphia.net wrote:
>
>
>
> >Since all the heat is at the bottom ( exhaust side of head) is it
> >nuts to consider running the air the other direction ? From bottom
> >to top, and out ? So the cool air hits the bottom first? Not to
> >cmplicate everything
> >  _______________________________________________
>
> Why not run headers, with individual runners angling out the sides,
> thus eliminating that hot exhaust manifold which would otherwise be
> radiating several thousand watts worth of heat back onto the bottom
> of the engine...?   Spit it out the exhaust and not worry about
> it.   A lot of heat would be eliminated this way, simply by keeping
> it from radiating back onto the bottom of the engine.   Exhaust
> headers have long since proven to aid engine cooling in almost any
> engine simply by helping to get rid of hot exhaust gasses quicker and
> via a pathway which doesn't involve heat radiation back into the engine.
>
> I've been well aware of how much raw heat sits there in those iron
> exhaust manifolds... eliminating them goes quite a way toward helping
> the engine remain cooler, especially on "cookdown" when a hot engine
> is shut off and sits there tinking and clinking, soaking heat off the
> iron manifolds into the heads and boiling the gas out of the carbs etc.
>
>
>
> tony..
>
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