With proven 1/4 miles in high 12s right off the showroom floor, or low-mid 13s
without any driving experience, all the while getting around 23 mpg average,
it's obvious these latest 4th-gen F-bodies are awesome performers. And, at base
prices starting around $20,000 for the Z28, they are the best
bang-for-buck values on the planet. This is thanks in part to their powerful LS1
power plant, which will be examined thoroughly next...
The all-new for '97 (98 for the F-body) LS1
was designed to be the epitome of General Motor's small block design, which
dates back to the design of the original Generation II (LT1/LT4) small blocks.
Thanks to their extensive development, GM was able to refine the design into
what is arguably the greatest small block ever built. Let's take a look at the
design of this engine in depth.
The Harness System
The bottom end of the LS1 is reinforced with the same cast nodular iron
crankshaft used in most previous small blocks, including the LT1/LT4. However,
it is noticeably shorter than that of a generic small block crank and the main
bearing size is larger than most, with the exception of the 400 cid engine. The
rod bearing journals are standard small block "large journal" fare,
pretty much the only component of the LS1 carried over from the generic small block.
All journals are rolled-fillet, introduced in the LT4. Another interesting note
about the LS1's crankshaft is that crankshaft end-thrust is accommodated by the center
main bearing instead of the rear main. The crankshaft is fastened with steel
6-bolt main bearing caps and 6.1 inch "powdered-metal" forged
connecting rods, topped with hypereutectic pistons that are much lighter than
the previous LT1/LT4, allowing for much faster revving.
Engine Block Design
The aluminum block requires extra strengthening for reliability and vibration
issues, so many external stiffening ribs are cast into the outside of the block,
as well as a lower skirt which extends beneath the crankshaft centerline. The
completed block weighs around 107 lbs, a full 53 lbs less than the LT1/LT4's
A bore size of 3.8976 inches (99 mm) combined with a stroke of 3.6620 inches (92
mm) equates to a total displacement of 5.665 liters or 345.69 cid. Of course, in
keeping with the Chevrolet tradition, it was rounded up to 5.7 liters, or 350
The Intake System
This killer bottom end is only the start of the advanced design. A new plastic
composite intake manifold is used for light weight and maximum flow (the best
way to quickly identify an LS1 is this manifold, which is flat black). The
plenum is beneath the runners, allowing them to be long, but also to flow
smoothly from their junction at the plenum, up and over to each intake port in
the heads. The LS1 uses a tuned intake port length similar to that of the L98 small block,
but features only 15" long runners instead of the L98's 21" runners
for best top-end power. This design is aided by the massive 58mm single throttle
body in front of the intake system.
The aluminum heads of the LS1 are of an all-new design, influenced by the LT4.
These block-toppers are sand cast of 356 aluminum, and heat-treated to the T6
specifications. The valve angle (the angle between the cylinder bore centerline
and valve stem), which influences the overall chamber shape and size as well as
spark plug position, is 15°, which is three degrees less than a NASCAR Winston
Cup small block head. With a 67.3 cc combustion chamber, the LS1's compression
ratio hangs at 10.2:1, just right for the street on high-test gasoline. This is
significantly lower than the LT4's static ratio of 10.8:1, but thanks to the
LS1's superior heads, it has a higher dynamic compression ratio. It should also
be noted that the generation of the flame front on these new heads is far
superior to the LT1/LT4 and therefore takes better to nitrous or boost.
Cylinder Head Port/Valve Design
One major feature of this new production head is what GM refers to as
"replicated ports". Previous Chevrolet V8 heads have two distinct
intake and exhaust port designs, but on the LS1, each intake port is identical
and each exhaust port is identical. This eliminates the problem of combustion
inconsistencies between the cylinders and create a uniform quality and quantity
of A/F flow.
Also aiding in the light weight are hollow-stemmed stainless steel valves,
2.00" intake, and 1.55" on the exhaust side. The intake port volume of
the LS1 is a rather massive 200 cc., with the exhaust port at a generous 70 cc
(and thanks to the 15° valve angle, the exhaust port has excellent flow
efficiency). The intake port is one of the most critical features of the LS1's
cylinder heads, which delivers a direct, straight path from the intake runner to
the intake valve, allowing maximum velocity and efficiency all throughout the
power band. This design is perfectly consistent on each cylinder for complete
balance. The fuel injectors, one per port, follow the same design and are aimed
DIRECTLY at each intake port for highest velocity and precise fuel delivery.
The valve train is completed with roller-tipped rockers and good ol' pushrods,
which were used mainly to keep costs down (designers looked back at the DOHC
32-valve LT5 from the Corvette ZR-1 to realize that), but also to keep overall
engine height to a minimum so it would fit under the C5 Corvette's sleek hood.
The LS1's camshaft is a steel-billet affair, and is rifle-drilled (read: hollow)
to reduce rotating mass. The LS1 cam has larger bearing journals compared to the
previous LT4, and all the lobes have bigger base circles. The lift is also
smaller than before, especially on the intake side. The LS1's redline is around
the same as the LT4, but with lower valve acceleration, the valve train has
greatly reduced mass and therefore softer valve springs can be used, which in
turn reduces the impact of the valve against the seat for added reliability.
The hydraulic roller lifters are another carry over from the previous small blocks,
and their centerlines are parallel to the valve stems and pushrods to greatly
reduce valve train deflection. The valve train is completed with cast steel
roller rockers, with a ratio of 1.7:1, 0.05 higher than the LT4's and .20 higher
than standard small block rocker arms. This higher ratio is to compensate for
the LS1 camshaft's lower overall lift. Thus, the overall intake lift is
.472" and exhaust lift checks in at .479". Designer John Juriga’s
noted in an interview...
"We didn’t go more aggressive on the cam, so at this point, the engine
has a lot of potential. First time out, we could meet our target with a camshaft
that is conservative."
One of the LS1's most serious advancements is in the ignition system. General
Motors began with the distributor less ignition system (DIS) in 1990 with the
LT5 small block, but now have gone one step further and created a separate
coil-per-cylinder system. Each cylinder has its own coil and coil driver assembly,
where a short plug wire runs from the coil to the plug. This allows less energy
loss (almost none) through the lead, and also reduces electromagnetic
interference with other on-board systems, such as the sound system.
Another VERY major change in the LS1 is the firing order. The new firing order
is 1 8 7 2 6 5 4 3, much different from the classic 1 8 4 3 6 5 7 2 sequence
which has existed in all Chevrolet small blocks for the past 5 decades. GM
stated that this reduced vibration and provided better idle qualities. Factory
spark plugs are AC Delco, platinum-tipped, similar to the plugs used in the
Exhaust System Design
The LS1 exhaust manifolds are hydro-formed, tubular stainless steel. They
feature a double-wall design which reduces heat loss between the cylinder head
and catalytic converters. Unlike the previous generation small blocks (LT1, LT4,
LT5), the catalytic converters are not mounted directly to the manifold outlet,
rather a further bit down the tubing.
The LS1 is advertised at 345 hp in the Corvette, 320 in the SS Camaro and 305 in
the Z28, but in many cases has dynoed (at the crank) far more. The horsepower
peak occurs at 5600 RPM and peak torque (advertised at 350 ft lbs) occurs at
4400 RPM. The maximum engine speed is 6200 RPM. Compared to the LT4, that's 15
more advertised horsepower, peaking 200 RPM lower, and 10 more ft lbs of
advertised torque, produced 100 RPM lower, and the torque band is much, much
Many Z28s with the "base" LS1 have dynoed at over 305 REAR WHEEL
horsepower, indicating how ridiculously underrated the engine is (click here
for a dyno sheet from user |_Z-28_|'s 1998 Z28 as one show of proof). In fact,
Corvette LS1's have often dynoed much less than Camaro SS', which have been
known to dyno as high as over 315 rear wheel horsepower. Impressive numbers
indeed, especially considering the total engine weight is 83 lbs. less than the
GenII small block. A strong rumor is circulating that GM will stop underrating
the F-Body LS1 in 2001, and finally admit its rated horsepower in the area of
Another important point to make in this mindset is the modability of the LS1.
The aftermarket had to scramble when the LS1 was first introduced, as they were
just getting properly established with the LT1/LT4 modifications. However, it
has already been seen in the past three years that the LS1 has potential for
extreme levels of power without serious modification. Needless to say, the
factory LS1 could be thought of as detuned, despite its already impressive
performance. As John Juriga pointed out, the camshaft is a fine example of an
area that could be radically modified. The compression could certainly be bumped
up if an LS1 was being built as a race-only engine, and both the Throttle Body
system, injectors and the exhaust system leaves plenty of room for improvement.
Aftermarket tuners like Lingenfelter
Performance Engineering also build stroker kits for the LS1 to bump the
displacement up. And example of a car with a similar kit is owned by ShamanWS6...
Another major aftermarket that is building around the LS1 and, indeed the entire
performance world, is turbo charging. Both Lingenfelter
and Incon offer twin turbo systems for the LS1. Lingenfelter's Stage I Twin
Turbo, in particular, has dynoed at 560 brake horsepower on about 6 psi of boost
on stock internal engine parts... certainly a true showing of the
potential of the stock LS1.
In comparison to the impressive performance engines of the '60s, the LS1
generates in the area of 400 gross horsepower, which is how engines were
rated then. This exceeds the original carbureted LT1's rating of 370 horsepower
and surpasses the horsepower rating of famous engines like the Mopar 440
Six-pack and Chevrolet 396, though torque is understandably lower than these.
It's also most impressive that the LS1 is the first two-valve V-8 engine to
reach the one-net-horsepower-per-cubic-inch rating. That is truly a great
title to hold, especially considering the production price of the LS1 cars.
It's obvious that the LS1 is one of the most advanced engine designs ever used
in a Chevrolet vehicle, yet not advanced to the point where it is absurdly
overpriced like many import engines that are considered "more
advanced". And it certainly follows Chevrolet's status as the best
manufacturer of "Bang-for-buck" performance... and this holds true for
both the Camaro and the legendary Corvette.