If you want to reposition the plug tip, it would be easier to get plugs
with a different "reach", the projection into the cylinder. As Walt
mentioned, piston clearance is a biggie. Remember, "If you play, you
must clay". A projected tip, hot spark and out further into the chamber
might be good, but might only show up on a dyno, and Walt mentioned they
go the other way.
I would go big spark, wide gap, with or without an MSD, and the position
of the plug won't matter as much.
Dave Brisco
-----Original Message-----
From: Walter Peterson [mailto:Walter.Peterson@cox.net]
Sent: Thursday, September 18, 2008 1:31 PM
To: 'Daryl Smith'; 'Steve Ehlers'; datsun-roadsters@autox.team.net
Subject: Re: [Roadsters] Spark Plug Seat?
Don't do it! The water jacket is too close and you could cause a leak.
This leak would require welding, re-machining the plug seat & new plug
threads. Yikes! Putting it back can be done but it takes an artist to
do
it.
In the racer world we added plug washers to space the plug out to
minimize
flame interference and clock the ground part of the plug to optimize
spark
exposure. Also we used a plug that was flush with the chamber wall, no
protrusion like the BP6ES.
Lastly, you wouldn't want to get the plug too close to the piston due to
heat & possible interference.
Most of the "How to modify your engine" books cover this. Good question
though.
Cheers Walt
From: Daryl Smith [mailto:drlsmith@dccnet.com]
Sent: Wednesday, September 17, 2008 11:29 PM
To: Steve Ehlers; Walter Peterson; datsun-roadsters@autox.team.net
Subject: Spark Plug Seat?
Just going over my R16 head and notice that the end of the spark plug is
about .030" to .040" inside the threaded chase at the combustion
chamber. On
the sparkplug itself, there is another .030"-.040" before the threads
start.........
Would it be beneficial for power and efficiency, albiet small, to
machine
the seat in the head to get the spark that .060" - .080" further into,
and
closer to, the center of the combustion chamber?
It isn't till the threads start that it will make a difference as far as
heat dissipation into the head, so the same contact area will be there
for
that......
Just throwing out ideas.......
Daryl
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