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Crate engines are hot items, and
for good reason: a huge selection of impressive power levels,
reasonable pricing and a warranty. These are just some of the
obvious reasons why crate engines have become so irresistible to
many enthusiasts who want to go fast and look good without the
hassle of building their own engines.
There are, however, those enthusiasts who still enjoy the personal
satisfaction of building their own engines, some with a fine
collection of new high-output components, and others more affordably
bolted together using swap-meet bargain parts. There are also those
enthusiasts with a strong sense of heritage who turn to vintage
parts for a particular look, and then there are the well-researched,
numbers-matching, production-like rebuilds. Whatever the reason for
deciding to build (or rebuild) your own engine, the goal is
generally to save money without skimping on the important aspects of
the build—in other words, getting the most horsepower for your buck
with a high degree of dependability.
With all the available crate-engine options for the Chevy small
block, we’ll look at a conventional small-block Chevy rebuild and
compare our horsepower numbers to that of a crate engine of the same
approximate power level, one closely matched to our home-built
engine. We’ll compare prices and the total investment vs. the
horsepower factor.
We built an engine on a low-budget theme, figuring this approach
might appeal to many readers, and if that’s not enough of a catch,
consider that we even had money left over for a small, used
supercharger. Bolting the engine to a dyno would have been an ideal
method of testing for comparative horsepower and torque, but that’s
not entirely feasible for everyone, so our solution was a little
more pedestrian, and within the means of most everyone—we used a
chassis dyno. And since our ’64 Corvette uses a manual transmission,
we figured on a 15 percent loss of driveline power to estimate
crankshaft horsepower of our budget-built engine. Actual dyno
numbers don’t always translate; what matters most is the power you
make to the wheels, so peak engine dyno numbers would not have
provided us much more than nice magazine reading material, which was
not our intent.
Lots of parts make up a turnkey engine, and those parts need to work
harmoniously together. There is no cheap way to build a performance
engine, just some more reasonable than others. For starters, quality
parts should be used in all cases, whether you plan to drive the car
on the street, blast down the local dragstrip, or occasionally drive
the vehicle on weekends. Whatever the case, the first step to
building a budget engine is finding a good block, and while we
struck gold with a pristine four-bolt-main 350ci block, there are
affordable heavy-duty iron blocks from companies such as Dart
Machinery, Bill Mitchell’s Hardcore Racing Products and of course
General Motors Performance Parts. The 3970010 casting we used was
assembled when we purchased it, and it was still at its original
4-inch bore. While showing no signs of cylinder damage, in spite of
us finding a damaged piston during disassembly, the block was a
solid foundation for our build.
We also found a donor small-block 350 engine with a good set of
forged flattop pistons and new GM rods. The engine had suffered a
few issues with its cylinder heads, but the bottom end was fine,
aside from the 0.040-inch rod and 0.060-inch main bearings to
compensate for a newly turned crankshaft. Frustration of another
builder turned into a great deal for us, as we snagged the donor
engine for only $200. After checking the pistons and rods, we used
them for our budget-built small block. We also purchased an Eagle
cast-steel crankshaft, and after the block was closely inspected,
measured and cleaned, we bought the appropriate rings, bearings and
gasket kit, which brought our total investment to $1,190, including
machine work, camshaft, cam gear, gaskets and essentials.
For the heads, we found what we thought was a good deal: a pair of
126 castings already fitted with larger valves, screw-in studs and
guideplates. The machine shop inspected the heads before installing
new valve-stem seals and a new set of valve springs to accommodate
0.575-inch lift. Admittedly, the cylinder heads were a bit of a $200
gamble, but they at least passed our visual inspection. The valves
were not sunk and there were no visible signs of gasket problems.
The ported GM castings were thought to work nicely with our
supercharged small block. The large combustion chambers are perfect
for our blown engine, while the 2.02- and 1.60-inch valves will
import and export plenty of fuel and air. As part of the short
block, we used a Comp Cams Nitrous HP camshaft with split duration
of 230 and 244 degrees, and 0.487- and 0.501-inch lift (intake and
exhaust), ground on a 113-degree lobe separation angle. The heads
and machine work added another $500.
For the induction, we added a used small-block Chevy 162ci B&M
blower, topped with a box-stock 750cfm Holley carburetor. Spark
comes from the original Corvette distributor, equipped with a
Mallory electronic module. Headman headers and Flowmaster mufflers
provide an unrestrictive path for the exhaust gases. Blower and carb
added $500 and $125, respectively.
After the engine assembly, installation and break-in, we dyno-tested
our Corvette at Speed Engineering in Decatur, Tennessee. The results
were somewhat disappointing, but no tuning was performed. Maximum
horsepower was 294 at 5,100 rpm, and torque was 330 lb-ft at just
over 4,000 rpm. This is final drive power at the wheels, so after
figuring in a 15 percent drive-train loss, we estimate engine output
at the crankshaft to be 345 hp and 380 lb-ft of torque. We would
have expected this without the blower, in naturally aspirated form!
With those numbers, a close crate engine is the Smeding Performance
383 Torquer, which makes 330 hp using some rather mild components.
For our total engine build, we have an investment of $2,315, but we
did not start out with all-new parts; we scrounged to find
appropriate deals on the used parts mentioned previously—pretty much
what any bargain hunter might do. Smeding’s 383 Torquer comes in at
$4,295 complete, but remember, that’s a sizable investment in
remanufactured and new internals, making its 383 a good deal for
anyone looking for a complete assembly, ready to bolt in.
If, however, you wish to spend less, although it might be hard to
duplicate our small investment exactly, unless you work at it, even
if you opt for all-new components, you can figure on saving a
considerable sum. But be careful—it’s quite possible to spend more
than what you can purchase an assembly for—reducing the upside to
the fact that you did the engine yourself. Another plus is that you
can pretty much make the engine power potential whatever you wish,
but that cannot happen without a “happy” mix of parts.
For our engine, actually a selection of problems could be at the
root of what we consider to be low horsepower output, but even then
there is little doubt that the engine made quite a difference in
this Corvette—it’s very quick on the street. A lightweight car with
4.11 gears can be deceiving, as this dyno-test and street
combination proves. We’ll tweak on the blower combination, and
perhaps try a different supercharger combination, but for now, the
engine runs well on the street, and its air/fuel ratio is at a safe
level (11.4 average). Even though our home-built engine has larger
valves, larger ports, a larger cam and more compression than the
Smeding Performance Torquer 383, aside from size, the two engines
are closely matched, which also means that the Smeding engine could
well provide an advantage in fuel costs. For starters, the blower is
designed to make 12 psi of boost (with the same pulley combination),
but 5 psi was the maximum boost achieved for our tests, which no
doubt had a huge impact on our lower-than-expected horsepower
numbers. But we’ll get to that in due time.
With proper tuning, our home-built engine has the potential to make
some serious power. This, however, underscores the primary advantage
to buying a crate engine (in this case a Smeding Performance
383)—the tuning and dyno time is already worked out for you. As our
results were well below expectations, these are the sorts of
problems that can occur when you do it on your own, requiring that
the combination be sorted out (over time). From our estimation, even
though the blower only made 5 psi boost, the engine alone should
have made that much power, if not more. Obviously, something isn’t
quite right with our combination, and we suspect the cylinder heads
for starters. Perhaps it’s the porting job or overall cam timing.
Either way, the engine is not producing over the expected 400 hp, so
for now we have what you might call the anti-dyno queen, but we
still enjoy driving it—it just needs a bit more tweaking on the
combination.
While we think this test was less than successful, our engine did
prove to be dependable. By comparison, the dyno numbers speak
volumes of the engineering efforts put forth by most crate motor
manufacturers—such as Smeding Performance—that must not only
engineer the power into the package, but substantiate that the power
can be duplicated engine to engine, and that the engine is
dependable. This is the true value of a crate motor.
No doubt building an engine is a great experience, and every car guy
should try it at least once, but it isn’t essential to get lasting
enjoyment from your car. Crate engines require less effort, and less
experience is needed to install, start and use one. Also, an
accompanying warranty (in Smeding’s case, two years) does give you
tremendous peace of mind.
The one big advantage we find in building our own engines at home is
the budget. If you are careful about the cost of components, and
find a good deal on the required machining, there is no doubt you
can build more power less expensively, as the cost of this test
proves. It also proves, however, that making horsepower at home is
easier said than done.
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