Can it be done? 20V head on a 2.3 NG?

[Fisher, Scott]

Dave Ullrich writes:

> OK, the NG makes 130 HP/140lb ft of torque stock and
> has a pretty high CR (10:1). So, if I bolt up this
> 20V head and it makes only 7:1 CR, what kind of power
> (hp & torque) will the engine make? Will I be better
> off or worse?

My most optimistic estimates say the best you'd do is +10 bhp, and that only
at very high RPM.  The standard rule of thumb is about 5% for each full
point in compression increase, so you're losing about 15% of your power by
dropping the CR three full points.  Let's just say for the sake of
bar-napkin calculations that your motor will only produce 85% of what it
would with the higher CR.  164 bhp (what my sometimes faulty memory says is
the rating for the 20V in the CQ) times 0.85 is 140 and a fraction.

More to the point, though, is that compression ratio has a HUGE effect on
throttle response -- lower CRs make for soggier throttle response, something
that naturally-aspirated 20V owners have expressed dissatisfaction with even
in stock form.  Dropping the CR to 7:1 would in all likelihood give you a
car that was significantly less fun to drive than the NG-equipped CGT.  In
short, there are probably far easier and more rewarding ways to get an
additional 10 bhp out of your NG than retrofitting a 20V head.

On the other hand, a 7:1 CR on a 20V head would be a GREAT candidate for
supercharging, which would be the way to bring back throttle response. :-)

--Scott Fisher
  Tualatin, Oregon