Re: Looking for a lonely 300 head

["James J." <m1garand@speakeasy.net>]

All,
   I've seen the iron heads which still had it (don't know if they all 
did, but the ones I saw did).  Also, the Rover heads still have them, 
although it's a different shape.  I'm just speculating here, but I know 
that you want your flame front to travel from one side of the cobustion 
chamber (CC)  to the other, which is why most CC's have the spark plug 
on one side.  If two flame fronts collide, they can produce a 
"detonation" like shock wave which can destroy cast pistons.  This is 
the danger from hot-spots that I talked about earlier.  What happens is 
that the spark plug fires on one side of the CC, and a glowing-red hot 
splinter (Ok, ok, aluminum doesn't turn red when it heats up, but you 
get my point and it would in an iron head) on the other side acts like a 
glow-plug and initiates a flame front there.  The two flame fronts move 
towards each other, compressing the remaining gasses inbetween them, 
like a piston in a disel engine.  The pressure rises twice 
(approximately) a quickly as it normaly would, creating a dynamic 
compression ratio much higher than the stock engine, and soon the 
detonation-retarding effect of the octane in the fuel is overcome and 
you get an explosion, vs. combustion.  On hemi and pent-roof CC's, the 
spark plug is in the middle, and so the flame front travels the same 
speed in all directions, so flame-front reflections aren't a problem.
   In the Buick and Rover heads (not Olds) we have what is called a 
semi-hemi (cool name for a band, eh?) CC.  This is where I start 
speculating:  I think the little "spark deflector" is more of a flame 
deflector or diverter and keeps the flame front from travelling the 
shortest distance to the wall, bouncing back and wreaking havoc.  This 
is only a guess, which is why I asked if anyone knew what it was, but I 
would be hesitant to remove it if, in fact, it does what I think.  Would 
love to know for sure.
   On a related note, I found a web page for an Aussie fellow who 
bolted post-'64 CAST-IRON Buick 300 heads on his Rover block, because 
the performance boost offset the weight penalty.  A few water holes had 
to be plugged (wonder why that changed between the aluminum and iron 
heads??) but it bolted right up.  His sight was one place where I saw 
the thingamabob on an iron head.
James J.

David Kernberger wrote:

> 12/18/03
>
> All,
>
> 	The keystone shaped thing is a "spark deflector" I was told when I
> asked the group about it a couple of years ago.  At that time nobody seemed
> concerned about its presence, absence, or condition.  It was my thought
> that it might be removed if one was needing to lower the CR a little bit.
> Apparently the cast iron heads on the 64 and later Buick 300s did not have
> them any more.  Once again, how about it, group?
>
> Regards,
> Dave Kernberger
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