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This article is in Chevy Rumble magazine January '08 edition.

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.


Thank you for visiting Speed Engineering and Dyno's Speed Ink Page. We hope this site will help to show you what we can offer for your late model car or truck. We offer many different services ranging from tune-ups to full performance engine builds. If you want the best service and tuning possible, then give us a call or send an e-mail. We will be more than happy to get you a quote on any part or talk with you about a full package. No matter what, Speed Engineering can meet your needs. Whether it is an aftermarket cold air intake, a Speed Engineering custom built 4" cat-back exhaust, a 400 RWHP bolt-on only X-Package, or a 427+ cubic inch blown monster. You have found the right place!

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