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| Re: Extreme A12 Head mods |
Subject: Re: Extreme A12 Head mods
by D on 2019/11/20 10:59:26
Some very clever suzuki bike racing guys spent quite some moneys
to raise the port of their drag race bikes and at the end
the result was 5% gain over their usual stock ports.
However the gain was right at the top end but sacrificed torque
in the low and mid range range enough to achieve slower times.
Toyota has achieved over 40% efficiency by going back to
less angled ports and biasing the inlet flow on one side
of the inlet valve and shrouding the other as much as possible.
This allows the charge to go deeper and with less turbulence
to achieve a very efficient and uniform swirl with small bores
but long stroke setup.
The deep chambers rather than shallow seem to also be the reason
Pontiac Buick nailhead v8s are so successful in racing since the 50s.
Getting the charge to miss the bore wall as much as possible but
swirl deep all the way to the bottom of the stroke is todays practice.
small high ports and smallish valves are better for very high rpm
which is usually a pig to drive on the street. Street tuner beware.
It all depends what you need but rebuilding your engine often and
changing the oil every day you drive it to its limits is not for every1.
Stock heads and ports are pretty decent performing units for street apps.
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