18
On the dyno, the SB4 7.0 winds up to 8,000 rpm to pro-
duce 750 horsepower on pump gas. Peak torque is a
strong 570 lb-ft, making this high-winding, LS-based power-
house a strong performer across the lofty rpm band.
19
Dimension-
ally, the
engine measures
30.3 inches at its
widest, in the front,
and is 27.1 inches
long and 17.1 inches
tall (from the crank-
shaft centerline
to the top of the
throttle bodies). As
for weight, it tips
the scales at 498
pounds, without an
accessory drive sys-
tem. And the black-
and-silver finish is
standard. Custom
colors and a carbon
fiber engine cover
are optional.The godfather himself, Zora Arkus-
Duntov, pushed for a DOHC Corvette
engine from the early days in his position
as chief engineer. Short of robbing a C4
ZR-1 of its powertrain, this is your best shot
and channeling his vision into your Vette.
VETTE
Mercury and the Building
of the Original LT 5
T
he original LT5 DOHC V-8 of the C4 ZR-1 was a technical marvel from
every point of view and perspective. It also represented a fascinating
departure from General Motors’ characteristically cloistered engine
development culture. The company reached out to Britain-based
Lotus Engineering for their overhead-cam expertise and tapped Mercury Marine’s
MerCruiser division to assemble the low-production engine. MerCruiser was
selected for, among other things, its decades-long experience with aluminum-
intense engines and its relative efficiency with low-volume production. More than
simply bolting the engine together, the MerCruiser facility performed a good deal
of CNC-based machine work on the aluminum components, adhering to Chevrolet’s
strict tolerances of as little as seven microns on most of them. That required design-
ing some all-new tooling, including a $750,000-investment in a custom cam tunnel
boring machine. Much of the engines’ assembly was performed by hand, before
each and every one was dyno-tested. The LT5’s balance and precise assembly made
for such a smooth-running engine that MerCruiser operations director Bud Agner
suggested a nickel would remain standing on end while the engine was running.
He was right. Search YouTube
for a look at MotorWeek’s visit of
the Mercury plant, wherein you’ll
learn that, for all the high-tech,
CNC machinery that went into the
assembly, workers used rattle-can
barbeque grille paint for the black
lettering on top of the intake mani-
fold. No kidding.Source
Roadster Shop
(847) 949-7637
http://www.roadstershop.com
17
A Mercury Racing-devel-
oped controller is included
with the crate engine kit.
56 VETTE 19.0 4
[ TECH]