Porting 101
Bruce Plecan
nacelp at bright.net
Fri Mar 13 02:19:59 GMT 1998
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In the mid 70's I spent a bunch of time play trying to
"improve" combustion chambers in the SOHC Ford 2000cc
pinto motor, and with some Mopar 340/360 stuff. As poor=20
as they appear, unless you have alot of past experience the
results can be disappointing. I ground up a few pinto heads,
and a few pairs of 340s. And I'll honestly say the results=20
were never very noticeable. Maybe a couple hundredths,
maybe .5 mph.. If you think you have to do something,=20
maybe a dremel, and smooth out some of the casting
(ie 3 mins/chamber). There was some gains to be made
in porting.
Porting on a SBC working around the valve guide, and=20
short side radius, OK. But, unless you've done it before
I wouldn't start on a good motor. Volunteer to help
someone else, that has a good base line, and document
what works. Work slowly, and get the knack for what
works. Better yet build a flow bench, and do it right.
Or be honest with yourself, and say I really don't know=20
much about what I'm doing here, and just gonna polish/
make em look pretty.=20
One of the places I worked at we cast, and machined=20
our own cylinder heads. Did alot of dyno/porting R+D
and looks don't mean much. Granted it sells parts, but
has nothing to do with performance.
As I understand the original poster this is for a boosted
engine. In that application, I'd start with a stock head
so there is a much mass for thermal loading as possible.
Start with a base line and work up from there.
HTH Bruce Happiness is a tailored Cone Shaped Hat
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<DIV><FONT color=3D#000000 size=3D2>In the mid 70's I spent a bunch of =
time play=20
trying to</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>"improve" combustion =
chambers in the=20
SOHC Ford 2000cc</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>pinto motor, and with some Mopar =
340/360=20
stuff. As poor </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>as they appear, unless you have alot =
of past=20
experience the</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>results can be disappointing. =
I ground up=20
a few </FONT><FONT color=3D#000000 size=3D2>pinto heads</FONT><FONT =
color=3D#000000=20
size=3D2>,</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>and a few pairs of 340s. And =
I'll=20
</FONT><FONT color=3D#000000 size=3D2>honestly </FONT><FONT =
color=3D#000000 size=3D2>say=20
</FONT><FONT color=3D#000000 size=3D2>the results </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>were never very noticeable. =20
May</FONT><FONT color=3D#000000 size=3D2>be a couple </FONT><FONT =
color=3D#000000=20
size=3D2>hundredths,</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>maybe .5 mph.. If you think =
you=20
</FONT><FONT color=3D#000000 size=3D2>have to do </FONT><FONT =
color=3D#000000=20
size=3D2>something, </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>maybe a dremel, and smooth out =
</FONT><FONT=20
color=3D#000000 size=3D2>some of the </FONT><FONT color=3D#000000=20
size=3D2>casting</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>(ie 3 mins/chamber). There was =
some gains=20
to be made</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT><FONT size=3D2>in =
porting.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2> Porting on a SBC working =
around the valve=20
guide, and </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>short side radius, OK. But, =
unless you've=20
done it before</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>I wouldn't start on a good =
motor. =20
Volunteer to help</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>someone else, that has a good base =
line, and=20
document</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>what works. Work slowly, and =
get the knack=20
for what</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>works. Better yet build =
a flow=20
bench, and do it right.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT><FONT size=3D2>Or be honest =
with yourself,=20
and say I really don't know </FONT></DIV>
<DIV><FONT size=3D2>much about what I'm doing here, and just gonna=20
polish/</FONT> </DIV>
<DIV><FONT size=3D2>make em look pretty. </FONT> </DIV>
<DIV><FONT size=3D2> One of the places I worked at we cast, and =
machined=20
</FONT></DIV>
<DIV><FONT size=3D2>our own cylinder heads. Did alot of =
dyno/porting=20
R+D</FONT></DIV>
<DIV><FONT size=3D2>and looks don't mean much. Granted it sells =
parts,=20
but</FONT></DIV>
<DIV><FONT size=3D2>has nothing to do with performance.</FONT></DIV>
<DIV><FONT size=3D2> As I understand the original poster this is =
for a=20
boosted</FONT></DIV>
<DIV><FONT size=3D2>engine. In that application, I'd start with a =
stock=20
head</FONT></DIV>
<DIV><FONT size=3D2>so there is a much mass for thermal loading as=20
possible.</FONT></DIV>
<DIV><FONT size=3D2>Start with a base line and work up from =
there.</FONT></DIV>
<DIV><FONT size=3D2> HTH Bruce Happiness is a tailored =
Cone=20
Shaped Hat</FONT></DIV></BODY></HTML>
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