[Roadsters] Spark Plug Seat?

[Daryl Smith]

  >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.<



  Looking at the head and into the waterjacket area, there appears to be
plenty of material for machining.........??



  >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.<



  I believe the original plug recommended for the roadster was the B6ES, I
understood part of the reason for going to the BP6ES was to get the actual
spark further into the combustion chamber, ie as close to centre of the
chamber as possible, exposing the spark to more of the fuel mixture.

  Yes, flame travel interference is a consideration, but since the plug is
initiating the spark, I would have assumed the plug would be thoroughly
engulfed in the flame long before this flame reached the other side of the
combustion chamber..........??

  Yep, I've read about plug indexing to have the spark plug ground "strap" out
of the way as much as possible....and that it worked....But, I'm thinking that
high energy ignition systems, large spark gaps, and specialty spark plugs have
got us past that nescessity.......



  >Lastly, you wouldn't want to get the plug too close to the piston due to
heat & possible interference.<



  With the gasket the highest portion of the plug (if the ground strap ever
ended up that way) is about .375" away on my head which is 3.20 inches thick,
lots of clearance for my flat top pistons, and it wouldn't be a problem for
the stock domed pistons either.......Custom racing pistons however....????



  >Most of the "How to modify your engine" books cover this.  Good question
though.<



  >Cheers Walt<



  Thanks for the comments and ideas, I'm off to the library to check out some
of those books!!

  Daryl

  Not happy with stock!







  From: Daryl Smith [mailto:drlsmith at dccnet.com]
  Sent: Wednesday, September 17, 2008 11:29 PM
  To: Steve Ehlers; Walter Peterson; datsun-roadsters at 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