<VV> RE: Lower shrouds

[Bill Elliott]

If you're measuring head temps in the stock sender location, that 
reading is influenced by the exhaust temps and is something like 75-100 
degrees hotter than the actual head temps (measured traditionally at the 
spark plug). In my fully laden 110/PG VW Westy, I can drive the head 
temps (measured at the plug) to 300 or so (roughly equivalent to your 
400 at the stock sender location) by lugging it down in top gear and 
full throttle up long hills;  well within the specs and the typical 
temps for air-cooled engines. The alternative measurement location is 
why Corvair temp specs seem so high to those well-versed in other 
air-cooled engines.

While the engine will quickly cool (either by shifting into Low or by 
cresting the hill) I don't think it's fast enough or far enough to be 
considered "shock cooling"... whether with or without bottom shrouds.

Bill

Pitts10ch at aol.com wrote:

>I live in CT and it is hilly around here of course.  I see 300 degrees  most 
>of the time when I am zipping around the curvy hills at power.  I do  see it 
>drop when on the back side of a hill about 50 degrees over a minute or  two.  
>With the shrouds on, I see 400 - 410 on the highway.  That seems  hot to me but 
>I come from aircraft engines and 400 + is pretty warm on that  front.  I can 
>see that I could be shock cooling on the backside of a hill  which causes 
>cracking in aircraft engines between the spark plug hole and the  exhaust valve.  
>Anyway, I think IL is probably a really safe bet on  the shroudless and I am 
>probably on the ragged edge when going down a long  hill.  Has anybody ever 
>heard of cracking jugs on these beasts?  If  that is not the concern what other 
>negative effects could over cooling  have?  
> 
>Fingers worn out,
> 
>Chris H.
>'66 140/4 
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