Port and polish refers to cleaning up the intake and exhaust ports for better
flow -
matching the openings in the head to the manifold openings (or vice versa),
removing
casting flash and polishing the exhaust ports for smoother flow. It is
advisable to leave
the inside surfaces of the intake ports in an "as-cast" finish. The slight
surface
roughness promotes boundary layer turbulence and aids in mixing the fuel-air
charge - at
least that was the theory when I was building motorcycle engines, back when
motorcycle
racing meant guys on Triumphs, BSAs and Harleys sitting up at the end of the
straightaway
on a mile oval and pitching that sucker sideways at 100 per, not some kid in a
clown suit
seeing how high he can jump, take both feet and one hand off the bike, wave to
the TV
cameras and live to tell about it...
bob_wilson@agilent.com wrote:
> Mike, P&P means Port and Pollish, right. I have heard of this (Home
> Improvement TV show) but don't exactly know what it is. I have a small
> machine shop in my garage and am fairly handy with tools. Is this something
> I could do myself? I believe it means to round off the corners of the
> intake "holes" in the head. I could do this on my mill with a "quarter
> round" end mill, or do you do this by hand with a grinder? Might be fun to
> do if it will help the engine perform better.
>
> My engine ('70 1600) is apart. Cylinders seem to be just barely out of spec
> for the standard size, so expect to go to the first oversize. This means
> new pistons, right? The amazing thing to me, considering that most of the
> things I have measured are not that worn, is that the cam seems to be REALLY
> WORN. It is supposed to have a lift of 0.335" or so (which I assume means
> the lobe-to-bottom distance minus the diameter of the non-lobe portion of
> the cam). I measure this to be about 0.235 which is 0.1" smaller!!! Yet the
> cam looks good visually. This is my first engine job and so am not
> experienced at this. This engine is the original in my '70 1600 and has
> about 180K miles on it.
>
> Boy, I got carried away with this. Sorry it is so long. ...guess since
> this is my "first time" I'm nervous about being sure to do everything right.
>
> Thanks for your response and that of the 4 others who responded to my
> question.
>
> Bob Wilson
>
> -----Original Message-----
> From: datsunmike [mailto:datsunmike@nyc.rr.com]
> Sent: Tuesday, August 15, 2000 4:08 PM
> To: bob_wilson@agilent.com
> Subject: Re: Engine Shop in San Jose?
>
> Bob,
>
> Get some head work done too. You know P&P and a nice 3 angle valve job. As a
> racing engine builder told my club the power is in the head!
>
> Mike
>
> ----- Original Message -----
> From: <bob_wilson@agilent.com>
> To: <datsun-roadsters@autox.team.net>
> Sent: Tuesday, August 15, 2000 10:32 AM
> Subject: Engine Shop in San Jose?
>
> > Can anyone recommend a good shop in the San Jose area where I can have my
> > engine work done? I have it all apart and need the crankshaft turned,
> > cylinders bored (I think), valves ground, ... 1970 1600 spl311-28383
> >
> > Bob Wilson
> >
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