Here’s a quote from T.O.O. from the late 90s. Even after 10 years this
sort of talk seems eccentric to most, including myself. David, I’d love to
hear your thoughts?
Quote:
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Originally Posted by Larry Widmer
The ability to induce the proper swirl frequency and depth of rotation is
paramount to maintaining a layered homogeneous mixture which will provide
a lengthened primary burn followed by a rapid secondary burn, all of which
will yield considerable resistance to detonation, greater over all combustion
efficiency and fewer bad guys coming out the exhaust. The over all time of
burn is so short and complete that the spark advance may be reduced to
the extent that you're not doing as much "negative work", and the exhaust
gas temperatures generally are in the 800 degree area, which means that
the heat of the burn provided considerable better thermal efficiency, and
something we and our competition noticed early on was the sound of the
exhaust....it was almost a "whisper" rather than what you'd normally hear
from an un muffled race engine.
I cast some small block Chevy heads back in the mid 80's, and although I
did rotate the deck to lessen the 23 degree valve angle, and reduce chamber
volume. The plug position was optimized, and of course the ports were
adequate, and the inlet ports were properly biased to promote swirl. The
pistons were "unique" in shape...all I'll say is they had no dish, except two
.120" valve reliefs. They were certainly of the domed variety. Those small
blocks were 358 cid. engines with 1.75-1 rod length to stroke ratio, very
short cam timing...235 degrees @ .050", and the intake manifolds were
some of my Edelbrock "specials" with Murray Jenson prepared Holley 830 cfm
carbs. Those engines had "over" 16-1 static CR, and dynamic compression
was so high we had to use custom starters run off 24 volts.
They were installed in some Camaros and two pick-up trucks. They all ran 91
octane unleaded pump gas. They never detonated; the mileage was 37
(combined) for the cars and 25 for the trucks. The Camaro's had Turbo 400
automatic transmissions, and from off idle you'd swear that there was at
least a 454 under the hood...the throttle response was almost too quick.
Those "loaded" cars all ran 12's with ease. The trucks had pulling ability that
no body imagined, and were a dream to drive, especially compared to their
street counterparts.
So, yes. If something as crude as a small block Chevy can be that efficient,
some of the more "modern" chambered heads can certainly do the same and
considerably better.
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Everything Larry talks about in the quote is common knowledge today so I look
for clues, how can he accomplish what most others cannot? I go back to when
he talks about the dome piston; that must be the secret. Now perhaps he was
doing something like the drawing I first posted. Or rather he could have utilized
the idea used in the piston he designed for the air cooled crowd using a dome
to evacuate the area under the intake valve. Here’s an example done for a
late model LT1.
