The inherent goal of hot rodding is, of course, to maximize the performance potential of your project. When selecting the components for a build, it can be tempting to instinctively turn to the beefiest hardware available to get the most output from your engine. But the reality is that a truly well-executed build is a careful balance of components, each tailored to one another in order to eek as much efficiency from the engine as possible.
Although the GM LS3 is a fairly stout performer right out of the box, it’s no secret that there’s huge potential waiting to be unlocked through aftermarket modification. Dart, among others, stands at the forefront of that development, offering blocks, crankshafts and cylinder heads that cater to those who are serious about getting big performance out of their engine.
Today we’re taking a closer look at Dart Pro1 LS3 cylinder heads (PN. 11030050) and assessing how to get the biggest performance benefit from them by seeing how they perform in some different scenarios in terms of engine configuration and natural aspiration versus adding a nitrous kit into the equation. As revealed here, it’s important to really get a sense of where your build lands in the ecosystem of high performance to ensure that these heads can really live up to their engineered potential.
Dart Pro1 LS3 Heads
With nearly a dozen different iterations of the LS series introduced since its debut in the ’97 Corvette and literally millions of engines produced in the two decades since, finding a great GM-based foundation to build power from has never been easier. And with the LS engine’s compact packaging and relative light weight, LS platforms have become the default choice for V8-powered engine swaps across the enthusiast landscape. For the LS3’s part, the factory-produced engine makes a very respectable 430 horsepower and 424 pound-feet of torque as it came installed in vehicles like the Corvette and Camaro.
But once you start digging into the internals to get more power out of the LS3, you can discover where there’s room for more performance beyond the capabilities of the stock cylinder heads. That’s where Richard Maskin and the folks at Dart come in with their Pro1 LS3 aluminum cylinder heads.
Developed with flexibility in mind, the Pro1 heads have been design to work with the stock LS3 valvetrain components and intake manifold, offering builders the ability to add these heads to their engines without the necessity of making dramatic changes elsewhere to accommodate them. This also provides those builders with stout foundation to grow into as they continue to modify the engine for additional performance or other applications down the road.
With a stock valve in the head and no porting other than a bowl blend these flow just over 370 cfm on the intake side at .800-inch lift, but it’s the exhaust side that’s the killer – these castings have 252 cfm of exhaust flow at .800-inch lift. – Richard Maskin, Dart Machinery
Yet while they’re compatible with the OEM gaskets, Dart has engineered larger port profiles into their design right out of the box, adding to the performance potential of these heads versus the factory units.
“With a stock valve in the head and no porting other than a bowl blend – which is what we do to all of our Pro1 heads – these flow just over 370 cfm on the intake side at .800-inch lift, but it’s the exhaust side that’s the killer,” explains Maskin. “These castings have 252 cfm of exhaust flow at .800-inch lift.”
Dart offers these heads in bare or fully-assembled form, with the latter providing a choice between either a 1.290-inch diameter beehive spring or a 1.295-inch dual spring, while copper-infiltrated valve seats, 8 mm manganese valve guides, and titanium retainers are standard.
The Right Combination For The Job
Dart recommends the Pro1 heads to be used with engines that have a 4.000-inch bore or larger, and when they say they’re intended for heavy duty applications, they’re talking about serious street machines and competition-level builds for circle track, drag racing, and other motorsport endeavors. So while they’ll certainly play nice with milder projects, to exploit the full potential of these heads, the engine has to be breathing hard enough to utilize what the Pro1 head has to offer.
Take for instance this build by Borowski Race Engines. It’s one of Dart’s 427 ci LS Next short-blocks outfitted with stock valvetrain components (including stock LS3 rocker arms), Dart’s Pro1 LS3 cylinder heads, and topped with an Edelbrock Super Victor Dominator-flanged LS3 manifold equipped with a Nitrous Outlet puck nitrous oxide system.
During dyno testing, Borowski saw the engine generate more than 600 horsepower without the use of nitrous, and that’s using a camshaft selected specifically for the presence of Nitrous Outlet puck system, which actually limits the engine’s full potential when operating without the spray. “It probably hurt our ‘on motor’ numbers by 75 horsepower or so,” explained Ken McCaul of Borowski. “I think the engine would make 650 to 675 if it were 11.0:1 compression with an NA cam, and had NA ring gaps set up.”
But this combination was built with spray in mind, and the results speak for themselves – 899.6 horsepower and 821.3 lb-ft of torque on pump gas with the aforementioned set of components along with the Nitrous Outlet puck system. “It really liked the combination. On pump gas with nitrous, we were real happy,” says McCaul.
Our Budget LS3 Versus Coyote Shootout, on the other hand, was configured with different intentions in mind and the results reflect that as well. We selected parts that fit within the confines of our shootout criteria, including stock or-near stock displacement, street-friendly camshafts, factory PCMs and a budget of $9,999.
Using the Chevy Performance’s factory CNC-ported LS3 heads, this engine produced 556.3 hp at 6,500 rpm and 498.0 lb-ft at 5,000 rpm – respectable numbers over stock given the rules of the shootout, but as the figures indicate, it’s a significantly milder build than the Borowski engine.
While the shootout engine’s output isn’t dramatically affected by the Dart head swap in its naturally aspirated configuration, adding nitrous to the mix gets the engine into the heads’ sweet spot, resulting in a healthy peak output of 735.6 horsepower and 633.4 pound-feet of torque at 6100 rpm. To bring the spray into the mix, we turned to Nitrous Express for their direct port kit for use with the FAST 102 intake manifold.
Nitrous Express To The Rescue
A safe rule for the novice nitrous user is you will be able to spray half as much nitrous horsepower as what the engine makes in a naturally aspirated application. – Ryan Lewis, Nitrous Express
“A safe rule for the novice nitrous user is you will be able to spray half as much nitrous horsepower as what the engine makes in a naturally aspirated application,” explains Ryan Lewis of Nitrous Express.
“So if the engine makes 400 horsepower naturally aspirated, then you should be able to spray 200 horsepower of nitrous safely. Of course we can spray more nitrous in select applications but the tuning window gets tighter as the shot size increases.”
Yet once you’ve sorted out which kit makes the most sense for the job, getting it to play nice with your engine is actually a fairly straightforward proposition. “The beauty of a wet system is that the nitrous system adds its own nitrous enrichment fuel so there is normally no need to adjust the fuel side of the ECU tune,” says Lewis. “The main tuning adjustment needed is retarding the timing 4 degrees per hundred horsepower.”
Nitrous Express’ system also takes a lot of the guesswork out of the installation by shipping their kit pre-plumbed into popular LS series intake manifolds like the FAST 102, the Holley Hi-Ram and the factory LS3 intake as well. The system includes eight nozzles, two NX Lightning-series nitrous solenoids and two fuel solenoids, as well as anodized aluminum distribution blocks, 3/16 stainless hard lines, and stainless steel fittings, all of which come plumbed on the manifold right out of the box.
While the Nitrous Express kit certainly takes a lot of the hassle out of fitting a nitrous system to your LS engine, you still need to be careful during tuning to prevent the possibility of internal damage. “Always double check your jetting patterns and make sure you follow the correct jetting pattern for the fuel pressure you choose to run,” Lewis cautions. “Always start on lower jet settings and work your way up slowly checking for issues as you move up on each jet setting until you finally reach your horsepower goal.”
Tuning aside, at the end of the day it’s clear that getting the most out of your build is about making sure your combination is properly balanced. In the case of our LS3 Budget Shootout engine, without a power adder the configuration simply wasn’t asking for enough from the cylinder heads to fully utilize the advantages of the Dart Pro1 cylinder head design. Adding the Nitrous Express kit pushed our LS3 into the Pro1’s sweet spot, and we have no doubt there’s a lot more left in it with just a few tweaks to the combination. It’s just another example of how much it pays to really sweat the details when selecting components for your build.
Advanced Cylinder Head Considerations
While we do have an all things nitrous article in the works (more on that soon), we felt it was important to at least touch on the more advanced cylinder head considerations such as wet flow testing versus dry flow bench testing, specific characteristics that make a cylinder head better for nitrous, and compatibility with future upgrades. For technical information like this, who better to talk to than the President of Dart Machinery, Richard Maskin?
“Really, wet flow testing is exactly what it sounds like,” says Maskin. “You’re mixing a fluorescent dyed liquid [with the same specific gravity as fuel] into the airstream and then the operator uses an ultraviolet light to measure precisely how much liquid and air flows through the engine as a specific amount of pressure, measured in inches of water [in -H2O], and whether the predetermined air/fuel ratio stays consistent.”
“You will hear guys commonly say something like, ‘I’m flowing 28 in -H2O.‘ Well, our custom built in-house wet flow bench is so powerful that it’s capable of flowing up to 55 in -H2O.” alluded Maskin. “After spending years and years swapping between dry and wet flow testing on just about every platform and application you can think of, Dart has found that if you flow test a cylinder head on a dry air flow bench at 28 in -H2O and then take the same head over to a wet bench, the values are not going to correlate.”
“We use a wet flow bench to show us exactly what the air fuel mixture will look like and is supposed to look like, so if we can make a head do something better wet than we can on a dry bench, it’s going to perform better in the car,” said Maskin. “So the best flowing dry head is not necessarily going to be the best flowing wet head or the best head in general.”
Okay, so now we know a wet flow bench is superior to your average dry flow bench because it more accurately simulates and measures how the air/fuel mixture will flow through the engine in real world operation. But does wet flowing have any particular benefits for nitrous builds specifically?
“Wet flow testing cylinder heads is universally beneficial to any engine, regardless of the platform or application,” explained Maskin. “Naturally aspirated, nitrous, nitromethane, blown, or turbocharged. If we can make it flow better on a wet bench than a dry bench, it will run better when it’s in the car.”
“Much like the end result of forced induction, nitrous engines make more power per cubic inch by introducing additional oxygen [and thus fuel] into the combustion chamber,” stated Maskin. “As the engine produces more power the heads want to be bigger so that they can supply enough air to mix with the fuel properly. As for these pro nitrous engines, we have found that the intake and exhaust ports want to be bigger and bigger as the engine makes more power. Exhaust port sizing is just as important as intake port sizing on these builds since we don’t want air and fuel stacking up on the intake side. We also modify the deck surface in various ways to ward off detonation, depending on the specifics of the build.”
“Again, the best wet flowing cylinder heads are going to be the best heads no matter what. Your specific engine and head combination is going to dictate how big you make the heads ports, what bore and valve size you use; even the stroke and RPM limit,” explains Maskin. “Power adders will always be introduced on the intake side, which means you want the very best flowing exhaust ports you can get. It doesn’t matter if it’s nitrous fed, boosted or normally aspirated, you want the exhaust ports to flow at their best.”
If you’ve already got a set of heads for your nitrous build and are planning to upgrade to an aftermarket block to increase cubes in the future, at the advice of Maskin, it would be a good idea to check your head selection again as well.
“Whether the heads will still work or not really depends on the head and engine combination you used to begin with,” says Maskin. “They may not be able to keep up with the nitrous if you’re making a big jump in displacement. Generally speaking, you probably won’t pull every bit of power out of the new engine as possible, but you will certainly see gains over a stock head. Will it be optimal? Probably not. Anytime you modify the block in any way you should always revisit the heads as well.”