Ego's a funny thing. There's nothing wrong with busting out the credit card and ordering up a crate motor, but most of us would never do it just because it would make us feel less manly. As a tech-heavy mag that's developed a following among hardcore DIYers, we'd expect nothing less from our discerning readers. The visceral thrill that comes from firing up a motor you built from scratch is what this hobby's all about. However, ego doesn't have to get in the way of learning. Although Smeding Performance is in the business of selling turnkey motors, you needn't compromise your manhood to appreciate expert advice.
Having built thousands of motors over the past 18 years, Ben Smeding and his crew have come across more wise guys like us than they can count. As such, Ben has a pretty thick stack of notes on how the average backyard mechanic does things versus the right way to get those same things done. Fortunately, he's willing to share that information with us. While most novices focus on things such as exotic cylinder heads and valvetrain components when building a motor, it's the little stuff like bearing clearances, ring packs, proper break-in, and optimized power curves that makes the difference between a stud and a dud. We felt so enlightened after our chat that we could feel ourselves reaching for our credit card, pride be damned.
I used to take great pride in being able to hone a block using old-style equipment. I thought I was a hot tamale, but then I got some automated machinery and realized that I wasn't.
People will always look at the price of a crate motor and its power output then proclaim they can build a similar combination for less money. According to Smeding Performance, convenience isn't the only advantage of buying a turnkey motor over assembling one in your garage. "After you build one motor, you realize your mistakes, but after you build 10, you realize what you can do better," Ben opines. "Only after you build 100 of the same motor do you finally know what you're doing. It's the little tiny things that make the difference in ultimate durability, like selecting the ideal ring package for an application. Similarly, different gaskets can distort a block differently, so with this knowledge you can compensate for that by using different torque plates."
One of the most common errors made in homebuilt motors that results in accelerated engine wear is setting bearing clearances incorrectly. Ben says just because off-the-shelf parts are sold in bundles, it doesn't mean they're compatible with one another. "Let's say you buy a rotating assembly and want to set your rod clearance at 0.0025 inch, but you have over 0.0030 inch," says Ben. "Most people would just assemble the motor as is, which would result in poor oil control and force the rings to work twice as hard to keep oil out of the cylinders. On the other hand, professional engine builders have the equipment necessary to adjust their machining to compensate for variations in clearances."We like to fit our pistons very tight, and the graphite coatings used in our motors with forged pistons helps accomplish that as well as reduce friction.
"Every motor we build is dyno'd and goes through a strict break-in process. We first fire up the motor and hold it between 2,000 and 2,500 rpm without any load placed on it at all. The timing is set, and once the engine reaches operating temperature, we set the idle mixture and place roughly 25 lb-ft of resistance on the motor. We gradually increase the load, which helps seat the rings, then tune the carb for idle quality, midrange power with and without load, and WOT. Next, the accelerator cam and squirters are adjusted on the carb. After one light-power run is made to 5,000 rpm, three full-power runs are made up to 6,000 rpm, at which time the engine usually picks up about 10 hp. Finally, a post-dyno inspection is performed to verify that there are no oil or coolant leaks. Customers receive the dyno printouts of their actual motor showing horsepower, torque, oil pressure, and water temperature from 2,500 to 6,000 rpm.
Most hot rodders use well-worn blocks as the foundation for their engine builds and never think twice about it. However, there are some drawbacks to using a block that has seen a fair amount of miles. "When a cylinder wears, it wears off to one side instead of wearing perfectly centered," Ben explains. "When you blueprint the block, are you going to machine it where it's at or machine it to blueprint specs? With most blocks, there just isn't enough meat to machine a cylinder to where it's supposed to be. Another benefit of using a new block is that there is no rust in the water jackets that could compromise the cooling system, and the newer casting technology is better as well."
In the right hands, battle-tested, old-school equipment is plenty capable of producing beautifully machined blocks, but there are significant advantages offered by modern computer-controlled equipment. The main benefit is consistency. "An automated machine doesn't care if it's in good or bad mood, so it will do what it's supposed to all the time," says Ben. "Automated boring fixtures ensure that the bores are properly located. Also, by combining automation with diamond cutters, honing machines can produce finishes that were unheard of just a few years ago, which results in faster break-in, reduced friction, superior ring seal, and improved durability."
The area under the curve, or average horsepower, is far more important in a street motor than peak horsepower. Consequently, a motor with lower peak horsepower can outrun a more powerful adversary at the track if its power curve is better optimized for its operating range and a vehicle's gearing. "The issue is performance throughout the entire power curve," says Ben. "If you take the dyno numbers of two engines, add up the power numbers they produce at each 500-rpm increment, then divide that sum by the number of increments, you get the average horsepower produced over the entire rpm range. A broad powerband with lots of low- and midrange torque may sacrifice some power up top, but it can still post a higher average horsepower figure than a peakier combination. That translates into better drivability and better track performance."It's nice to have power at peak rpm, but when you go to accelerate in most instances, you're at a lower rpm. Nothing's nicer than gassing it at 2,500 and having the car take off.
"A lot changed in the piston industry due to advancements in CNC machining and diamond cutters. Pistons can be made much more accurately now, so whether they're forged or hypereutectic, they will fit very tightly in the bore. That means piston slap associated with forged pistons doesn't necessarily compromise durability, as previously thought. However, we actually use hypereutectic pistons in many of our motors because they're more rigid and fit slightly tighter in the bore, which can reduce blow-by and noise at startup. Hypereutectic pistons are very rigid and strong, but once you reach a certain power output, they'll break. On the other hand, forged pistons will flex and move because the material is much softer, which is why they can handle more power. Ultimately, it's a trade-off."
The Other 383
Smeding's 383 packages use a 3.800-inch crank over the more common 3.750-inch cranks. While Smeding's crankshafts are custom, GMPP offers 3.800-inch-stroke units as well. Since this less common stroke requires a custom piston, is there any performance advantage to using it over a 3.750-inch stroke? "The main reason we have our cranks custom made is so we can set our clearances more precisely and tailor the counterweights to be more in balance with our components," explains Ben. "Since we're doing that, you might as well take advantage of the extra stroke of a 3.800-inch crank. This allows us to run higher compression with lower-grade fuel due to the improved quench. In theory, a longer stroke should rotate easier because of the additional leverage, which reduces stress, improves durability, and might improve gas mileage as well."
Some engine builders say break-in isn't necessary due to advancements in ring technology, while other suggest a stringent break-in procedure. So who's right? "It all depends on the honing technique and the type of rings and bearings used, which is why there are so many different opinions on break-in procedure," says Ben. "Since we run every motor we build on the dyno, they're 90-95 percent done right out of the crate, and our customers don't need to do anything. Whichever break-in procedure you should adhere to is up to your engine builder or machinist to determine. There isn't a universal answer."
Anything greater than 91-octane pump gas is hard to find out west. Consequently, whether it's blower kits or crate motors, most engine components are now tuned to be compatible with 91-octane fuel. Rest assured, Ben says the drawbacks of a few octane points are minuscule. "If you have access to 92- or 93-octane fuel and bump up the timing accordingly, the benefit is so small that it's not even worth doing. There's always a trade-off. Advancing timing can boost midrange torque but will also sacrifice some top-end power."
Forced induction calls for lower compression, but there are other engine parameters that must be tweaked to make it compatible with boost. In addition to thicker compression heights and stronger wrist pins, forced induction requires different bearing clearances, ring packs, spring pressures, and exhaust valves and guides. "Forced induction makes blow-by worse, so standard-tension rings help improve oil control better than the low-tension rings used in many naturally aspirated motors," explains Ben. "Larger bearing clearances improve oil flow, and valvespring pressures must be increased since boost tries to blow the valves open. The additional heat of a blower motor also mandates the use of additional valveguide clearance and wider seats."
Freshly built motors require more frequent initial oil changes to adequately flush out metal particles from the brand-new internal components. While some enthusiasts suggest drain intervals as frequent as 500 miles for the first few thousand miles, this may be overkill. "At our shop, we do the first change after a motor has first been run on the dyno," explains Ben. "The next change should be performed at 1,000 miles, then every 3,000 miles thereafter. If using synthetic oil, the drain intervals can be extended to 5,000 miles."
Big cams make big power. It's as simple as that. As glorious as that may seem, Ben advises against them for street motors. In order to operate power brakes and accessories, he suggests running a cam that will yield between 10 and 12 inches of vacuum. "Large cams might sound neat, but it's better to have a slightly milder camshaft," he opines. "Not only do they drive better, but they offer better gas mileage as well. All of our crate engines are compatible with power brakes and accessories."
"People like to joke that it's impossible to build a small-block Chevy that doesn't leak oil, but we don't agree. We have customers all over world, and the last thing we want is a customer in Norway with a leak that we have to fix. Leaks were common with older blocks, which required regular retightening of the pan bolts, but that isn't necessary these days. We use one-piece silicon pan gaskets with integral gromments that prevent overtightening, as well as one-piece rear main seals. After a motor is dyno'd, we double-check it for leaks. A common cause of leaks is when people try to save a few bucks by reusing a stock pan in a stroker motor. If you beat on the pan near the rail for more clearance and distort it, you're asking for trouble. Our customers buy our motors because they expect quality, so if you have one out of 100 with a leak, that's not acceptable."
Leave it to the Experts
"We always get customers trying to reinvent the wheel with trick new cams and intake manifolds. We've already been through all that. Since we've been building motors for many different shops and racers for a long time, we have a solid network of feedback from experts inside the industry in terms of cutting-edge components and new engine-building techniques. The truth is, if there is something better out there, we would have figured it out before the general public and we'd be using it already in our motors. By dealing directly with parts manufacturers, we're kept in the loop on innovations. If they know of some new techniques that improve power or durability, we'll jump on it right away." CHP
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