vortec heads

[ECMnut at aol.com]

Yup. I totally agree.  Quench is critical.
I Have relatives that build/run NHRA super stock engines.
Both Chebbie & Mopar.  The tight quench area is a given
in their minds.  They spend time trying to make pistons
lighter, and doing litttle stuff with the ports.. The NHRA rules are
pretty strict with factory compression ratios, OEM port CC's etc.  
Imagine shifting a steel rod 454 @ 8500+ rpm.
With turbos, I'm not in need light pistons, just durable ones.
What they get from RPM and .800 lift roller cams, I'll more 
than make up for in boost and electronics.
MV.

> For SB Chevy, GM calls for .035 min piston to head clearance.
>  Linfenfelter calls for .040.
>  It's called "Quench" and according to Lingenfelter it squishes out
>  the air and fuel and the turbulence (And the it's so close fuel can't
>  detonate in the space) helps prevent detonation.
>  Mark
>  ----- Original Message -----
>  From: "Bruce Plecan" <nacelp at bright.net>
>  To: <gmecm at diy-efi.org>
>  Sent: Saturday, December 16, 2000 2:20 PM
>  Subject: Re: vortec heads
>  
>  
>  >
>  > Your correct on all counts.
>  > far better to use a dished piston, to even further min the squish area, 
CR
>  > permitting.   You want to get the greatest volume of gas as close to the
>  > plug as possible.
>  > PS   Just remember that rods stretch a far amount at high rpm
>  > Bruce
>  >
>  >
>  >
>  > > One more thing that I have heard is very critical with SBCs is the
>  > clearance
>  > > between the top of the piston and the flat machined part of the head (I
>  > think
>  > > this is what they refer to as the 'squish' area).  This should be kept
>  to
>  > a
>  > > minimum.  I have heard that putting in thick head gaskets to lower the
>  > > compression ratio will actually cause MORE detonation due to having
>  > increased
>  > > this clearence.
>  > > I probably got some of my terminology wrong, so somebody please
>  straighten
>  > me
>  > > out!
>  > > Ted
>  >
>  > > > I'll tell ya, since I can't get the GN to detonate (with what I call 
a
>  > > >  reasonalbe tune), next motor is gonna be a 9 or 9.2ish CR job (with
>  > barrier
>  > > >  coatings).....
>  > > >  The Regal has flat tops for 9.5 with a 56cc chamber (AL), and that 
is
>  > > >  another one that is another one that is real hard to detonate.
>  > > >
>  > > >  The GN has run 20d timing at 20 PSI of  boost on 92 Octane, and only
>  > once
>  > > >  did it tickle the K/S and that was on the 2-3 shift for 2d.  40#er
>  > > >  injectors.  I think the smooth chambers, and 195 operating temp with
>  > the
>  > > >  cooling system right are the big answers here.
>  > > >  Bruce
>  >
>  > 
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