Don't Trust the Interwebs
The massive Internet message board community with its innumerable niches has spawned the rise of the Internet expert-almost all of which are completely self-inflated and unreliable sources. Mike Phillips of Automotive Machine and Performance says he deals with this issue all the time in his shop and the various Buick "experts" tend to only spread a great deal of misinformation causing him to have to reeducate his customers to gain their trust. While there are often nuggets of truth, Phillips says just stay skeptical and assume everything you read on a message board is either exaggerated, hearsay, or downright incorrect, and you'll seldom be disappointed.
Check Your Ego
Tying in nicely with Mike Phillips advice is Racing Engine Designs' Bret Bowers' tip: When you go to speak to your engine builder, check your ego at the door. Unless you have years of engine-building experience under your belt and genuinely have an informed opinion with which to bench race your potential combination, let your engine builder be the expert. Much like you wouldn't hang over a mechanical engineer's shoulder and give advice on a project after just reading a couple of books or taking a class or two, there's really nothing you're going to be able to tell an experienced engine builder. What you need is a level of trust, so Bowers recommends doing your research first to find builders with experience with your particular engine of choice, and then speaking with them about your goals and your car rather than about specific parts or specs.
You may be able to build an extremely powerful race engine once, but are you prepared for the regular teardowns and maintenance...
Be Realistic About Your Plans
This tip from Clark Hinkle of Hinkle Performance Engines is one that will save time, money, and frustration. Before buying a single part or talking to a builder, be brutally honest with yourself about how you'll be using the engine. Everyone loves to bench race and brag about big power numbers on the dyno, but that's not the right thing to focus on if you want to get the most enjoyment out of it. Instead, ask yourself exactly what the car will be used for and what the typical operating range will be. Picture it in your head. An engine designed as a high-revving strip/strip combo, for example, would be a terrible choice for a heavy car that'll spend most of its time on the street cruising in lower rpm range. Along those same lines, make sure to talk to your engine builder about the car the engine will be going in. The curb weight and driveline combination will all factor into nailing down the right parts choice to build an enjoyable engine. And lastly, for street cars, stop focusing on peak power numbers; strong average horsepower and torque will yield a much more fun driver.
Plan for Aluminum
The evolution toward factory and aftermarket aluminum engines has brought great benefits to hot rodding, including lighter weight and better cooling, but building an aluminum engine requires slightly different planning, says Lanny Trefz of Shelby Engine. Aluminum reacts to heat differently than iron and expands more significantly, which requires the internal tolerances to be adjusted to compensate. How much adjustment is required will depend on the particular engine platform and parts chosen, but in general Trefz recommends slightly tighter clearances on the bearings and valvetrain, and placing the piston higher in the deck.
Control Your Geeks
Advanced EFI technology is a fantastic thing that allows a few keystrokes to alter just about any point of an engine's performance and driving manners. That can yield fantastic results, like radical, high-power combinations that are surprisingly street friendly, but the problem is that you can also dig deep into the tables chasing a level of perfection that's unachievable. Hot Head's Bob Holmes explained that while there may be a theoretically perfect group of specs that would result in the ideal tune, in practice, it's more like a range of specs. Case in point: In preparation for the EMC, the Hot Heads team once spent a solid weekend making over 200 dyno pulls and constantly making minor adjustments to the engine and the tune. In the end, they gained almost nothing, except a lot of wear on the engine. At the highest levels of competition, this may be justifiable for minute gains, but in the world of street cars and even weekend warriors, constant tweaking of the tune becomes more of an academic debate than a practical result.
You Need More Carb
You've likely seen one of the formulas that supposedly yields a ballpark number for the cfm of air your carb will need to flow for a given engine:
(Cubic-inch displacement × 2) - 15% = cfm
Cubic-inch displacement x maximum rpm / 3,456 = cfm at 100% volumetric efficiency
Scott Main and Bob Moore from MPG Heads say, both formulas will result in a seriously undersized carb for a performance engine. They also caution against the old adage that says undercarbing is better than over; they would much rather see a carb that's a little too big rather than one that is restricting airflow. Then again, going too big can create issues as well, especially on a street car. The bad news is that there isn't a foolproof formula that you can punch a few numbers into to yield the right carb for your engine. The only real way to get the right carb for your engine combo is relying on the experience of engine builders or racers to help you hone in what will yield the right results. If you don't have a good resource to ask, our general rule of thumb for hot street cars is to use one of the formulas for a starting point, then step up to the next cfm size and tune it within an inch of its life with the aid of a chassis dyno.
Work on the Intake Flow
An engine is simply an air pump driven by controlled explosions, and power production is simply a function of how much air an engine can move and how quickly it can do it. With that in mind, Judson Massengill of the School of Automotive Machinists (SAM) advises that for maximum power, never stop working on the intake flow through the heads since that number will set the ceiling for the engine's potential. Through careful porting and shaping of the ports, the goal is to create the most cfm flow possible through the heads because that will determine how the rest of the engine needs to be spec'd. It's a particularly important metric to know when getting ready to choose the camshaft profile since the cam functions as the gate that allows air into and out of the combustion chamber. Knowing how much air the head can move throughout the lift range will help determine the right lift, duration, and even ramp speed for the profile.
Don't Get Boost Greedy
Boost is king for making big power while keeping daily driveability, especially on late-model cars. While there are some nicely prepackaged systems for popular cars that take the hard work out of forced induction, the issue Tony Bischoff of BES Racing Engines says he sees too often is when guys start getting boost greedy. Most aftermarket "bolt-on" kits are low-boost applications designed to keep the engine within a safe power range and are intended to be left alone. When guys want more boost, they tend to forget that everything needs to adjusted to compensate, especially the tune. A proper tune is the only thing keeping the engine from damage, but too often Tony sees guys who want to add parts, but not pay for the time to have the tune altered to compensate. Those guys usually end up at his shop needing their engines rebuilt.
Mock it Up & Measure
Since Adney Brown specializes in crankshafts at Performance Crankshaft, his tip naturally flows from his decades of experience there. Too often customers call him with vague specs for their crankshafts that often prove to be incorrect. The remedy here is to mock up your engine like you're doing final assembly. Before sending your crank to a shop to be ground, torque it into the block (assuming it has already been machined) with the correct bearings and take careful measurements in the right location. All bearings are designed to be crushed into place. Since this crush tends to push the bearing insert toward the crankshaft journal, the bearings are tapered to increase the clearance and prevent journal contact. Because of this, you should always measure the inside diameter of the bearing perpendicular to the parting line to find the smallest inside diameter of the bearing. That's one of the numbers Adney needs when grinding any crankshaft.
Bigger is Not Always Better
There is a tendency when planning a new engine to go right for the big numbers: the biggest cam, the biggest heads, the most compression, and so on. We occasionally fall victim to that ourselves. The problem is, that's the wrong attitude to take, no matter what the intended purpose for the engine, because bigger is not always better, and less can be more. Just because part numbers exists at the far end of a list doesn't mean they will be compatible. As a matter of fact, they may be poor choices. For example on a street engine, Jesse Robinson of SKMFX says he would prefer heads that flow less than those designed for wide-open throttle racing since they can help create quicker throttle response and more low-end torque. The same with compression: It may yield more power, but it also yields a more finicky engine that creates more heat and strain on itself. It's always best to temper the desire for big number bragging rights in favor of properly sized components.
Everything is a System
The biggest issue Mark McKeown sees with his customers is a failure to realize that a powerful engine does not equal a quick car. And that's a problem for him because the knee-jerk reaction is to assume it's the engine builder's fault. The problem is usually that guys have forgotten that effectively putting down power in a useful way requires configuring the rest of the drivetrain and chassis to channel the power to the ground. You'd be amazed how slow a muscle car with a 450hp engine can be when nothing else has been upgraded. When power output changes the relationship, it's time to reevaluate your car.
Speed Costs Money. How Fast Do You Want to Go?
The crew of the University of Northwestern Ohio (UNOH) where the EMC takes place is also loaded with talent and experience, and UNOH instructor Paul Higgins said we were missing the very first and most basic thing you have to ask yourself: What's your budget? It's easy to bench race and dream big, but when it comes to writing the check, what are you willing to part with? "I've often been asked something like, 'How much would it cost for you to build me an engine.' " Higgins says. "I tell them $50K. When they say that's too much, I say, 'Well tell me your budget and we'll go from there.' " Equally important, Higgins says, is considering what the care and feeding of the engine will be afterward. You may be able to build an extremely powerful race engine once, but are you prepared for the regular teardowns and maintenance it will require and the inevitable breakage? If not, step back from the razor's edge on your combination and increase the longevity of the engine.