<VV> Squish area article in Pop Sci mag -Long -little Corvair

Geoffrey A Johnson geoffj@unm.edu
Thu, 19 Aug 2004 08:37:06 -0600 (MDT)

Two reasons why you usually do not want such grooves in the chamber.  One 
for the reason you mentioned, hot spots that could lead to detonation. 
Two, In areas like this it can cause a skin effect where unburned fuel can 
remain after combustion, and then go out as exhaust leading to increaded 
emissions.  This is also a problem in using a high quench setup, as the 
cooling that is the desired result also leads to some waste of fuel, and 
increased emissions.  The reson usually seen with pinging in vair motors 
is increased combustion chamber temperature over water cooled motors, 
and often not as good fuel mixture from the built in intake manifolds.  If 
you are looking to mill the step out of a set of 
regular heads, use 95's or 80's instead of 110's, or 102's respectively. 
This will provide usually a better Compression Ratio after the step being 
removed with minimal need for correction.  This is how we have built 
several motors we are happy with.

-Geoff Johnson
63 Monza CP ULTRA 110 Engine
66 Corsa CP w/Milled 140
64 Greenbrier w/Milled 95
62 Greenbrier w/Milled 80

On Thu, 19 Aug 2004, cash case wrote:

> Sorry for the double post on VV and FV, but I would like to here as
> many opinions on this as possible.
> This is a very interesting article.
> For those interested I'd go buy the sept 2004 issue.
> Since some of our Corvair engines seems to have pre-detonation problems
> I read this with interest. After reading I wonder if modifying some 110
> heads this way wouldn't be an intriguing test.
> What this fellow's doing seems completely wrong. He is cutting a series
> of grooves in the combustion area in the head. His thoughts were to
> cause even more turbulence then just having a squish area. They've got
> pictures in the article showing some of the modified heads. I don't
> know how the heads are not detonating all over the place.
> He apparently has been trying for years to get some one in the
> automotive industry to notice his work. Usually he just gets blown off,
> but he finally got permission from an engine manufacturer to test his
> work on a dynamometer. The only engine manufacturer that would allow
> him to do the tests was Briggs and Stratton.
> Apparently its very hard to get this kind of thing done in the middle
> of India, that's where this guy's from.
> The fellow got his data back and and in the article claims the data
> says that from 2000 rpms to 2800 the modified engine used between 10
> and 42 percent less fuel and yet seemed to have no appreciable loss in
> torque or power then an unmodified twin motor running the same tests.
> I bring this up because we usually try to get any sharp or semi sharp
> edges out of our Corvair heads. Some of the grooves this guy cuts into
> the heads are in a radial pattern emanating from the spark plug area.
> Is there a peculiarity in the Corvair heads or engine that causes them
> to detonate more frequently then newer cars or is it just a compression
> problem.
> Very cool article!
> [demime 0.98e removed an attachment of type image/jpeg which had a name of cash face.jpg]
> Cash Case
> "Some people are like slinkies.
> They're not worth much,
> but you can't help but smile
> when they tumble down the stairs!"
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