Custom Sleeves 88mm-90mm (opinions)

[Robert Legere]

--- "P@" <bossman@customsteel.com> wrote:
> So, any one else want to chime in on this subject?
> I know you are just
> itching to put in your two cents on this project.
>:-)

*****I'm curious how this works out. Specifically, the
pricing issues at hand. Also, is there a commercially
available deck plate for the SR20? I'm not fond of
shipping a block across the country....
     This should be a nice modification for those with
ported heads and larger valves. I've found the stock
SR20 bore shrouds the valves too much, reducing
airflow especially with larger valves. Cars built for
the BTCC found this out too, they were bored to 88 mm
and destroked to 82 mm to meet the 2.0 litre rules and
allow for better breathing. Piston speed was not the
issue there with the restricted rpms in the BTCC. The
Formula 2 rally cars with NA SR20's retained the stock
bore/stroke ratio and still revved to 9200.
     I presume too that JWT will have to build a
custom ECU program for 'big-bore' engines to optimize
the ignition timing for a larger bore engine...
probably more initial timing due to the greater flame
travel distance. The engines may be sensitive to
detonation at higher rpms though.
     Head gaskets? What is commercially out there for
a big-bore engine?
     I was interested in building an 89 mm bore engine
personally, but would consider 90 mm if the wall
thickness was adequate. Most engine builders of
cast-iron bore blocks consider .125"-.130" the
absolute minimum. Any more and the cylinders flex
appreciably enough to affect ring seal. Turbo engines?
Forget the huge bores, they REALLY flex if the wall
thickness is inadequate. Same with NOS applications.
I'd probably limit an NA engine to 90 mm for
street/strip use, and 89 mm for race use (sustained
high rpms and high compression). For turbo I'd stay at
88 mm or smaller, just to be safe. The additional hp
gained from the larger bore will be lost via the
leaking rings, perhaps more.
   Just my opinions....

Bob