NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/rec/autos/tech/17583

Text File | 1993-01-08 | 2.0 KB | 46 lines

Newsgroups: rec.autos.tech
Path: sparky!uunet!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!sorlin
From: [e-mail] (Steven J Orlin)
Subject: Re: porting the heads
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Date: Fri, 8 Jan 1993 16:43:15 GMT
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In article <[e-mail]> [e-mail] (Chris Ne
ugebauer) writes:
>In many discussions or articles on high-performance engines,
>one thing that I frequently see mentioned is that 'they ported
>the heads'.  What exactly does this mean?  How much of a power
>increase is this sort of thing good for?


Most engines,(not blueprinted), from the factory, have heads which can
be considerably modified to increase, not necessarily torque, but top end
horsepower, from higher gaseous flow.
     Reason being is that these heads are made on a budget and cannot each
be individually put on a flow bench and get the right metal hogged out
in the right places, to increase flow.  Instead, the factories make a practical
design which can be cast inexpensively and will work satisfactorily in the
engine.   (To make a long story shorter)

     On say, a V8, the areas which can be trimmed to increase flow (correct me
if I'm wrong) are around the valve guide boss, and the roof of the port.
Of course, there are many other modifications you can make to the heads (three
angle valves and so forth).

     As far as the power increase on an unmodified engine, I'd guess at
between 10%-15% in overall horsepower.  For an already modified engine, it
depends on what all the engine has to utilize the porting job ( ie. manifold,
carb, cam...)

steve
--
"Nobody tells a Navy man when he's had enough to drink, cause only a Navy man
 knows when he's had enough to drink!"
-Steven J Orlin   [e-mail]  /\/\/\/\/\/\/\/\/\/\/\/\/