Sounds like you have hit pay dirt Jack. This only proves again that "One
valid test is worth 10,000 expert opinions". What I ws refering to primairly
was that the flat tops gave a more effecient combustion therefore you gained
more power with a lower ratio and less chance of detonation. But I never
argue with a guy who has found a way to be fast.
----- Original Message -----
From: Jack Wheeler <jwheeler@robus.com>
To: 'Kas Kastner' <kaskas@earthlink.net>
Cc: 'FOT' <fot@autox.team.net>; Bob Kramer <rgk@flash.net>
Sent: Monday, October 11, 1999 1:14 PM
Subject: RE: TR compression vs. HP
> Kas, I don't think my experience is completely contradictory to yours.
> First, my pistons were custom made by me with a die grinder to get a good
> fit into the combustion chamber. As a result, the pop-up part of the
> piston was more like a dome which projected into the combustion chamber.
I
> don't remember the exact height, but I think they were about .140" above
> the normal height of a flat top piston.
>
> Our (I have to give credit for the idea to Hardy, who suggested I try
> pop-ups in about 1983) objective was not to create a better flame pattern,
> or more efficient combustion. At least in my case, the sole objective was
> to get the higher compression without having to mill the heads any
further.
> With flat tops, I was milling almost .200", and most head castings
> wouldn't last long with this much milled off them. After investing all
the
> money to port and polish a head, I needed for it to last a few years. By
> using the pop-ups, I was able to get the 13:1 compression and only had to
> mill the head .150". The heads lasted forever.
>
> I also found a considerable improvement in power with the higher
> compression. With everything the same except the cylinder head and
> pistons, I went from 155 HP with flat tops to 167 HP with the pop ups.
> The new head may have been better, and the dynos were different, but the
> order of magnitude increase we saw on the dyno related directly to
improved
> times on the track. My conclusion is that the increase in compression
more
> than offset and 'confusion' caused by the pop-ups.
>
> This analysis does not follow the scientific method completely, but it
made
> sense to me at the time and, as we said, "the proof of the pudding is in
> the lap times". Does this make sense?
>
> -----Original Message-----
> From: Kas Kastner [SMTP:kaskas@earthlink.net]
> Sent: Monday, October 11, 1999 12:42 PM
> To: Bob Kramer; Jack Wheeler
> Cc: 'FOT'
> Subject: Re: TR compression vs. HP
>
> The issue of pop-up pistons has come to the fore several times over the
> years and the information never seems to be saved or passed. To wit: I
made
> a series of engines for exp. purposes in the early 60's to view the
> effects
> of compression ratio increases. In a nut shell here is what I found on an
> honest engine dyno with an operator that didn't lie to himself (me). The
> 13:1 pop-up piston that entered the combustion chamber confused the flame
> pattern in the combustion chamber so much that the measured BHP was the
> same
> as an engine with flat top pistons and 10.25 ratio. The slightly domed
> pistons were better than the pop-up by a considerable measure but NONE
were
> as good as the flat top. The combustion chamber in the wet sleeve engine
> series is so ancient that there is not room for a decent flame front to
> progress. Look at the tops of your pistons if you have the pop-up or
domed
> type. See if the carbon is a reddish or off color brown instead of black
> and that there are swirl type patterns on the piston top as opposed to a
> flat covering of carbon. Generally you will find exactly that as I have
> described. The flat top piston allows the flame front to progress evenly
to
> the back of the combustion chamber and reach there before the end gas has
> time to heat up and explode on its own (detonation). On the flat top
> pistons
> you should see that the carbon is thinnest or maybe even non-existence on
> the squish area side of the piston and closest to the exhaust valve
because
> this is where the detonation is going to occur. I ran cast pistons for
> years
> and years in these engines both the stock 83mm,86mm and the Hepolite 87mm.
> The Hepolite in my opinion was a great deal better as it was a lot lighter
> than the stock castings. When we ran forged pistons they indeed had the
> longevity but did not produce the power as the bore clearance was twice
> that
> of the cast pistons and they were quite a bit heavier.. The thing here
> being
> that if you control the detonation you can run a cast piston. Of course I
> am speaking from efforts 30 years ago but gasoline still is supposed to
> burn
> not explode so maybe some of this is still true. The best and most
powerful
> engine I made were done with 87mm cast pistons, chrome compression ring
and
> .003" bore clearance. To eliminate the run in time and additional wear on
> the engine I lapped all the rings into the individual mating sleeve and
had
> the highest effective compression immediately and it showed on the
> racetrack. With all my work in these areas I have a small caveat that must
> be remembered, and this is that I was only interested in something to last
> the weekend not the year and there is the "wolf in the bush" Kas.
>
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