Legend has it that 30 seconds after Nikolaus Otto, the German engineer credited with developing the conventional four-stroke internal-combustion engine, successfully demonstrated his invention, his buddy Deiter – who was reportedly wearing a “Der Edelbrock” patch on his oil-stained lederhosen – asked: “Can you maken zee engine mit more horsepower?”
And so it began – the eternal quest for higher performance. If you’re even only a passive enthusiast, you know that at its core, Otto’s world-changing contribution to modern civilization is an air pump. The more air that it can process, the more power the engine can make.
We qualified that description with the word “can,” because capability and fulfillment are two different things. There are many attributes to engine-performance optimization that limit an engine from fulfilling its full capability. Some of the limitations are driven by an engine’s specifications, such as its displacement, while others are driven by factors such as excessive friction or restrictions that rob horsepower.
Polling 100 different engine builders would return 100 different opinions for maximizing performance, but there are some long-established and proven methods for reducing internal losses in the engine to make the most of what it has to offer. For this story, we’ve outlined 15 of the tips and tricks that through our experiences have shown to be the most effective for enhancing performance relatively easily and cost-effectively.
Of course, options such as power-adders and stroker combinations deliver huge gains, but we gave this story parameters that limited the recommendations to non-power-adders such as supercharging and/or nitrous oxide, and changes that didn’t require removal of the engine for upgrades. That meant no stroker kits or anything like that.
With those parameters, we’ve come up with a strong list for the do-it-yourselfer, even though some of the recommendations are more involved than others. The bottom line is there is horsepower hiding under the valve covers of your Chevy’s engine. You’ve just got to dig them out!
As Bruce Springsteen said, you can’t start a fire without a spark. It’s the very essence of combustion, so the strongest, most effective spark that can be generated in the combustion chamber will help make more horsepower. If you’ve got an older engine without a GM HEI (high energy ignition) distributor, make the conversion. You’ll also want to consider a hotter ignition coil or even a supplemental ignition box like the venerable MSD 6A-type to pick up the HEI’s known slack at higher rpm. And here’s a tip for those running an LS engine: Unless you’re nearing the 1,000-horsepower level, there’s no need to change the stock ignition coils. They’re good as-is.
It sounds almost beyond basic, but don’t take your spark plugs for granted. For one thing, the gap should be checked to ensure it is optimal. If you’ve upgraded the ignition system, for example, with a hotter coil or an MSD box, you will probably want to increase the gap a bit. MSD says that a typical gap of 0.028-inch can be increased to about 0.032-0.034-inch. You may also want to go with a plug with a colder heat range, too, which helps pull heat away from the firing tip faster and prevent power-killing problems such as detonation. The rule of thumb is one heat range colder for every 75-100 horsepower you add.
Timing is Everything
If you’ve never experimented with ignition timing adjustments, grab yourself a timing light and dig in. Even minor adjustments can pay big dividends in real-world performance, especially if you’ve performed the ignition upgrades noted previously. And if you commit your car to a strict diet of premium gas, you can see significant horsepower gains by advancing the spark. Give it a try and push the timing in 1- or 2-degree increments. If you get to the point of detonation, you’ve gone too far and need to back it off a couple of degrees. No big whoop. This is the perfect complement to the optimized ignition system.
This is an oldie but a goodie when it comes to releasing pent-up horsepower: Remove the factory engine-driven fan and replace it with an electric cooling fan system. The change relieves the engine of a source of parasitic drag, which costs horsepower. Even an engine-driven clutch fan can turn at about 30 percent of the water pump speed when not in use, so getting rid of the engine fan altogether enhances performance. It also contributes to longer water pump life. Admittedly, the performance gain is not akin to dropping a big blue bottle of nitrous in the trunk, but every little bit helps – and dual-fan setups can provide better cooling capability for a hotter engine.
To be honest, factory small-block heads used up to the mid-1990s weren’t great. They were OK for making up to about 300-350 horsepower, but offered about zilch in high-rpm airflow. That changed with the Vortec heads developed for GM’s truck engines. Their kidney bean-shaped “fast burn” combustion chamber design was efficient and the port design, while optimized for lower-rpm torque, offered surprisingly good high-rpm airflow, relatively speaking. If you want more than 350 horsepower from your 350 small-block, they’re the way to go. They’re cheap, too, in factory iron versions.
This tip isn’t so much about extracting more power from your Chevy’s engine, but reducing its weight to help improve the launch and overall performance characteristics of the vehicle. By changing over to aluminum cylinder heads and an aluminum intake manifold, you can remove 50-60 pounds off the nose of your car, which helps significantly with weight transfer under acceleration – more so when you’re talking about a big-block. Sure, aluminum heads are more expensive, but not prohibitively so. It’s a smart investment if you’re not willing to bypass the Krispy Kreme on the way to work each day.
Porting for Power
Another tried-and-true power-building technique is porting the cylinder heads, which involves enlarging the intake and/or exhaust ports to increase their airflow capacity. It can also involve smoothing the passages or removing cast-in impediments to airflow, as well as working the bowl area of the combustion chamber. It’s a job that can be tackled at home by the novice, but you’ll want to consult an expert or two before grinding away, because removing too much material or removing it in the wrong place can cost horsepower. In fact, if you’re working with rectangular port big-block heads, you probably don’t need to touch the already large intake ports. Focus on the exhaust ports. Do your homework first or trust the job to a professional.
More Squeeze Please
While you’ve got the heads off the engine, you might as well have them milled a couple of hundredths to not only ensure they’re warp-free, but also provide a smidge more compression that contributes to higher horsepower. A full point rise in compression ratio will typically net a 5 percent horsepower increase. That works out to an approximately 0.040-inch flat-mill of the deck surface – and that’s aggressive. Generally speaking, go with something like a 0.020- or 0.025-inch spec to ensure an adequately thick deck and adequate piston-to-valve clearance. If it looks like there’s sufficient piston-to-valve clearance, you can complement the cut with a thinner head gasket to make up the difference and get closer to the full point increase in compression.
With heads still off the engine, you may also want to consider having the heads machined to accept larger valves, which allow more air to flow in and out of the combustion chamber. For the small-block, 2.020- or even 2.055-inch intake valves and 1.550-inch exhaust valves do the trick, while those big-block rectangular-port heads for example, benefit from 2.250-inch intake and 1.880-inch exhaust valves. Don’t skimp on the valves themselves, either. Get the good, stainless parts. If it were us spending your money, however, we’d probably just suck it up and buy a set of already ported aluminum heads that also had larger valves, so you could just pull them out of the box and bolt them on the engine.
Whether you’ve had the heads ported – and especially if you have – port-matching them with the intake manifold helps ensure smooth, uninterrupted airflow from the intake into the heads. It’s a trickier job than it sounds, because of the casting variances for the different components involved, but when done correctly, it’s a machining detail that can really help optimize the velocity of the air/fuel charge for greater performance. On the quick and cheap, you can also trim the intake manifold gasket to ensure none of its material blocks the edges of the intake ports on the heads, which would restrict airflow or cause unwanted turbulence in the head.
Rockers and Rolling
One of the easiest and most cost-effective ways to reduce engine friction to free up horsepower is replacing the stock, stamped steel rocker arms with lightweight, aluminum roller rocker arms. There has been more than a little controversy about whether a rocker arm with only a roller tip is worth the investment, given the relatively modest effect on performance it delivers. The LS engine family, for example, use non-roller-tip rockers, but with roller fulcrums. The upgrade you really want is a set of rocker arms with roller tips and roller-type fulcrums. And since you’re spending money, get the aluminum-body rockers, too, which help reduce weight on the valvetrain, which can be worth a few rpm. Get them with a higher ratio, as well, such as 1.6 vs. 1.5, which effectively provides more valve lift for greater performance.
Believe in Beehives
Another learning from LS engines is the high-rpm advantage that comes with beehive-type valvesprings. Companies such as COMP Cams and even Chevrolet Performance offer beehive conversion kits and the advantages are clear: They offer greater valvetrain stability and a much lighter valvetrain. That’s achieved with less spring pressure with better valve control and reduced weight of both the spring and retainer. That means the engine can rev higher more safely, allowing, say, a small-block with a good-flowing ported head to rev into LS territory and make comparable power. It’s an upgrade you should strongly consider when you’ve got the heads off your engine.
We couldn’t get through a list of basic performance upgrades and not mention the camshaft. The thing is, it would be impossible to recommend one grind or another, because every engine and use is different. We’ll say, however, that it’s an upgrade that can be done in most cases with the engine still in the vehicle and it’s one that can deliver a tremendous difference in performance, as long as it’s selected properly. In short, don’t guess with a new cam. Talk to one of the cam companies’ tech lines and tell them the parameters and planned use for the engine, because if you get it wrong, the new cam will flat-out kill performance and/or driveability. One more thing: If you’re using the engine primarily on the street, you want a hydraulic roller cam.
The Roller Tip is Hip
The significant reduction in friction and benefit to long-term durability delivered by roller-tip lifters makes the change to a roller-style camshaft all the more important. The reduction in friction over an old-school flat tappet-style camshaft system builds real horsepower. Surprisingly, factory roller engines didn’t appear in Chevy cars until the late 1980s and in the 1990s for some trucks – and that was only the small-block, so there are plenty of enthusiasts rolling around out there without a roller engine. The 1987-later SBC block casting has provisions for the roller cam and the “spider” used with the roller-tip lifters, but earlier engines can be converted relatively easy, but at a generally higher cost, because of some additional components required to keep the camshaft from “walking” in the block. You’ll need an appropriate valvetrain, too, so it’s a good excuse to pop for those beehive springs mentioned earlier.
Get Exhausted … When it’s Time
Here’s the requisite advice about using freer-flowing headers in place of the heavy, restrictive factory exhaust manifolds. It’s legit, too, because if you’ve made enhancements to push more air through the engine, you’ll need to get it out quickly. However, it’s not necessarily an upgrade you need to make immediately, because the cost/benefit ratio for headers on later-model vehicles such as fourth- and fifth-gen Camaros and C5, C6, and C7 Corvettes doesn’t really become positive until a number of other mods have been made first. Those later-model vehicles have comparatively efficient factory exhaust systems so the bang for the buck isn’t realized until you’ve done a camshaft, freer-flowing heads, etc. The manifolds on earlier cars, however, were restrictive logs, so don’t worry about ditching them. The sooner the better, too.