TEXT FPO - Driving Sports TV

sO YOU haVe copious amounts of smoke pour-
ing from your tailpipe, you have that “thud” from
the starter when you turn the key, and your car is
making less power. Chances are, you have a blown
engine. If you are going to swim in the performance
tuning pool, you will have to at some point dive into
the deep end, and that means rebuilding an injured
engine. a fair amount of casual tuners will want to
try to push their setups to the edge of what a stock
block can take and then pray that something doesn’t
go wrong. however, in a world of dodgy gas, high
ambient temperatures and less-than-stellar tuning,
the chances of some amount of knock causing engine
failure are pretty good. Then there are those of
us who, despite better judgment or sage advice, just
want to “turn up the boost” past what is reasonable
or safe. You know who you are.
Knowing that at some point your engine will fail
is a good place to start from. having that knowledge
in the back of your mind, and perhaps some rainyday
cash set aside, will help ease the blow-by.
having done extensive modifications to our
2007 Legacy Gt, and also having done some rather
hardcore driving on and off the track with our car,
it was only a matter of time before the stock eJ255
bottom end would give out.
and so it did at our secret test track. after a hard
day of lapping oil-smoke would billow from the tailpipe
on startup. We also had the telltale “whump”
52 July 2008
Smoke: not good.
“We chose to go a middle road that is
a solid and popular choice...”
on startup. Usually when you start your car, for
those first few cranks before the engine fires, the engine
will turn over smoothly and uniformly. On a car
with a dead piston the engine will “thud” unevenly.
Combined, these two symptoms should be enough
to let you know something is amiss. The next step is
a compression and leak-down test. sure enough, we
had 140psi of compression in three of four cylinders,
with cylinder number 4 being the low man on the
totem pole with only 75psi of compression.
Once you know for certain that your engine is
toast, you have several options. The first, and probably
the easiest, method is to just buy a new stI
shortblock from the dealer. These are relatively inexpensive
at around $2,000 and are a direct replacement
for all 2.5-liter turbo Imprezas, Foresters and
Legacies. For 2.0-liter cars, you can use your WRX
heads on top of the 2.5-liter block; however, you will
need to use a thicker head gasket readily available
from Cometic.
The next easiest but a bit more expensive option
is to buy an aftermarket shortblock. These are usually
stI shortblocks with forged aluminum pistons
in place of the stock units. blocks like the Crawford
s2 are a great way to bolster your engine without
breaking the bank.
Of course you can buy engines that take this
much further, like blocks built by Cosworth. These
engines, while quite expensive, feature upgraded
rods, billet crank, race bearings and forged pistons.
These engines are very durable and are made for
extreme performance conditions; a bit overkill for a
road car, but a very good option nonetheless.
Then there is the build-it option. If you have
never built an engine, we would recommend hiring
a professional machine shop for this route. The
upside here is that you get to choose exactly how
you want your engine to be assembled and what
components to use. The downside is that choosing
the proper components, especially if you are going
all out with rods and a new crank, etc., can be a bit
daunting, but research and perhaps a guiding hand
from your tuning shop of choice can ease that burden.
We chose to go a middle road that is a solid and
popular choice with subaru tuners: the “drop-in”
piston in a fresh stI shortblock. One of the virtues of
the subaru engine design is that the pistons can be
removed without splitting the block or even removing
the rods and crank. This means that you can purchase
a factory-built shortblock and simply replace
the pistons with forged stock bore-size units without
having to re-torque the main and rod bearings. This
makes building a solid and very stout subaru engine
very simple. Keep in mind this is specific to subaru,
and your buddy with the evo will have to remove the
bottom end to perform the same upgrade.
There are currently several pistons on the mar-