Last month, we brought you the interesting prototype short-block from Pro Line Racing which is part of the Red engine development program. Now, we’re bringing you an inside look at the top half of the engine, without giving away too many secrets. There is an incredible level of development and refinement in this combination, which will translate into affordable production pieces, just like the theory with the bottom-end components.
Creating a new top-end for an engine might not sound that incredible in today’s 3D-scanning, CNC-machining-anything-you-want-out-of-billet world, but when you stop and realize the production goals of the project (to offer everything in a cast version with a reasonable, easy-to-keep-on-the-shelf price point) you start to realize the gravity of the project.
While this article will showcase the components and some of the effort that has gone into the project, no single magazine article can truly convey the amount of time and effort expended by multiple companies, all working together in order to bring truly elevated parts to market, all at an accessible price point to boot. With that, let’s get to the shiny bits!
Dart’s 20X Raised Port Cylinder Heads
If you’ve been around the big-block Chevy world, you’ve undoubtedly at least heard of Dart’s Pro 1 20-degree CNC cylinder head. However, when you’re Pro Line Racing, “good” isn’t good enough. While the Pro 1 is hardly a slouch, Pro Line and Dart got together and decided to take the heads to the next level, by designing the Red 20X cylinder head. Yes, there are a few similarities between the heads, like the valve angle. But, beyond that, it’s a whole new ball game.
“We worked with Dart and their R&D team to develop an all-new big-block Chevrolet technology package for the sportsman racer that was cost-effective and generated extreme horsepower with reliability,” says Eric Dillard, Pro Line Racing’s co-owner. “Dart has always been known for their ability to develop these types of engine packages and they delivered with precision.”
Mike Sanders, Dart’s Product Development Manager, explained that there was indeed a significant development process in designing the Red 20X heads. “We started with our standard 20-degree casting and welded up the areas in the rocker valley that needed material to support the new rocker system,” Sanders says, alluding to the fact that the largest focus of the new cylinder head design was improving the valvetrain for reliability. The inherent performance increase was a secondary benefit. “It all came together really well and by the results Pro Line has seen on the dyno it’s a home run.”
First, since it’s in the name, let’s look at the valve angles of the Red 20X. As is implied, the intake valve angle has been rolled over to 20 degrees, which is six degrees more vertical than the stock angle. The intake valves retain the stock four-degree cant angle of the original big-block Chevrolet cylinder head design.
On the exhaust side, the valve has been rolled four degrees for a 13-degree angle, while, like the intake, maintaining the original four-degree cant. The importance of the valves having the same cant angle will become clear as we dive into the valvetrain changes later in the article.
The combustion chamber has been optimized for a 4.500-inch bore, with a small (by big-block standards, at least) 90cc chamber volume in order to provide elevated compression ratios with a better (flatter) piston crown design. The chamber houses 2.500-inch intake and 1.960-inch exhaust valve seats made from Copper-Beryllium. They have been machined with a five-angle valve-job with a 55-degree seat angle (which was once thought to be impossible in a forced-induction application) on the intake and a 50-degree seat angle on the exhaust, and then blended to maximize fuel shear.
The intake ports are a monstrous 485cc in volume, which are quite a bit larger than the standard Pro1 heads. Size isn’t everything — Pro Line and Dart worked to optimize the port design, not just hog out the existing port shape. “Port efficiency is always our number one objective when it comes to designing a cylinder head,” says Sanders.
“Whether it’s naturally aspirated or forced induction, we adhere to strict parameters in terms of cross-sectional area and velocity, so the air does not become turbulent and cause the fuel to fall out of suspension. The main area of focus for this design was the intake port and chamber to help produce optimal cylinder fill, fuel distribution under pressure. Once we were able to straighten out the pushrod, besides getting the better geometry, we were able to move the port around even more, and make it even more of a straight shot to the valve”
On the exhaust side, the 20X has ports similar to the standard 20-degree head, with a few specific changes. “Normally, our bolt holes break through the exhaust runners, because of the locations of the bolts,” explains Sanders. “It’s not a huge deal, but Pro Line wanted to make sure that there wasn’t any exposed bolts in the exhaust, so we shifted our machining by about .100-inch to the side. That didn’t really hurt anything to shift it, and left a completely intact port wall.”
Sealing the amount of horsepower that this will generate can sometimes be a challenge. In order to do that effectively, Pro Line relies on Dart’s 7/16-inch head stud kit, manufactured by ARP, specifically for i’s 20-degree cylinder heads being used on an aluminum block. To seal the surfaces of the block and head together, an SCE no-water design, solid copper head gasket was used, measuring .080-inch thick.
In order to contain the amount of cylinder pressure expected in this combination, Pro Line takes the additional step of O-ringing the cylinder heads. By cutting a groove in the cylinder head, slightly larger than the engine’s bore diameter and then fitting a round wire into the groove, it focuses the clamping force of the cylinder head into an even pressure point that surrounds the cylinder, acting like an impenetrable wall to combustion gasses, increasing the amount of cylinder pressure the combination can withstand.
Straightening Things Out in the Valvetrain
As we mentioned in the previous installment of the Red engine project, one of the main design goals was to improve the valvetrain geometry. Primarily, the goal was to straighten out the pushrods, in order to provide strength and stability at 9,000 rpm. “The lifter positions and bank angles in the block were all dictated by the cylinder head,” explains Sanders.
That said, it’s not a matter of just enlarging a pushrod hole in the casting to accommodate these design goals. In fact, it is quite an undertaking, which involved designing a whole new rocker arm system as well. “The development process was like most R&D projects we develop,” explains Sanders. “Once we added the material we’d need to mount the new rocker system, we then built a custom stand model for the left port, right port, and exhaust port with the correct pivot length.”
While that sounds relatively straightforward, designing an intake and exhaust rocker arm which provides the proper geometry the team was looking for was a challenging task. However, once the specific design was achieved, computers made creating the rest of the set a lot easier. “Once we had the designs we were happy with, we digitized them and duplicated the design across the remaining cylinders to create the one-piece rocker bar,” Sanders explains.
“From there we were able to straighten out the pushrods by moving the lifter locations and bank angles into a custom layout that allowed us to fit a large 9/16-inch diameter exhaust pushrod and 1/2-inch diameter intake pushrod for maximum stability, all while making sure that the sweeping geometry was perfect. It all came together really well and by the results Pro Line has seen on the dyno it’s a home run.”
On the manufacturing side of the rocker arm design is T&D Machine Products, which is known for its rocker arm systems. During the R&D process, T&D built rocker arms both from 2024 aluminum and one of its proprietary billet steel alloys, with the steel eventually getting the nod. In building the set, the real innovation, according to T&D’s Sheldon Miller, is in the stand design, and the rocker arms themselves are pretty traditional.
It’s not often that you see a one-piece rocker stand, with integrated intake and exhaust rocker-arm mounts, for a big-block Chevy, but the team made it happen, all while keeping the rocker arms completely straight for the added strength and stiffness. The rocker ratio chosen for the project is 1.7:1, and like everything else in the valvetrain, was built around a specific valve length and camshaft lift in mind. That’s how specific this Red design is.
Speaking of valves, this combination uses titanium units in both the intake and exhaust positions from Ferrea Racing Components. Measuring 2.400 inches wide by 6.030 inches long on the intake side and 1.800 inches wide by 5.930 inches long on the exhaust side, both feature a stout 11/32 stem, as well as Ferrea’s Chromium Nitride (CrN) valve coating. By coating the valves with Chromium Nitride (CrN), Ferrea increases the valve’s resistance to wear, friction, and galling.
Controlling those valves is a set of PAC Racing Springs dual valvesprings. With installed heights of 2.120 inches on the intake and 2.180 inches on the exhaust, these are definitely stout springs, and quite well-engineered to be able to be stable and control the valves at the engine’s 9,000-rpm redline. Combining strength and light weight, PAC’s 10-degree Solid-Stop titanium spring retainers were used, along with PAC steel 10-degree square-groove locks. Because of the increased loads on the valve tips in an engine with this much lift and spring pressure, lash caps are utilized. Once again, PAC supplied a set of its .080-inch thick lash 11/32-inch lash caps made from the company’s proprietary “Super High Strength Steel” alloy designed for extreme wear resistance.
Riding on the keyed .937 Jesel solid-roller lifters are a set of massive pushrods from Trend Performance. Measuring 1/2-inch diameter on the intake and an extra-thick 9/16-inches diameter exhaust pushrod, the double-taper pushrods are designed to combat the extreme dynamic loads and pressures they will see thanks to both extreme RPM and boost pressure.
The Master Gatekeeper of Airflow
One of the trickest components on the engine is the insane billet intake manifold. Coming from the long-time supplier of Pro Line’s various billet intake manifolds, the Red’s billet intake from Magnatron is no different. Since the Red engine project is designed as a forced-induction combination, it makes sense that this intake manifold has been designed specifically for big-boost applications.
When you are cramming atmosphere into an engine at three-plus-times standard atmospheric pressure, different flow dynamics start coming into play. Looking at the inlet of the intake, it’s immediately obvious that something is different about this design. The single V-band connection splits into two 90mm circular openings. While we’ve seen some dual inlet and even oval throttle bodies, before, this is different, with two 90mm throttle plates connected to a common shaft, which operate in unison.
While two 90mm throttle bodies will flow well north of 2,400 cfm of air, which is way more than enough air volume to feed this engine, even at full boost, the dual arrangement is less about absolute airflow capacity and more about flow dynamics within the intake itself. Since this is an all-out racing engine, there are no concerns about being able to modulate the throttle on the street, and the massive airflow will allow the intake to breathe freely at 9,000 rpm. A set of SCE Accu-Seal Pro intake gaskets keep the intake sealed to the cylinder head with standard ARP BBC intake bolts.
Since this engine will be running on Methanol, and methanol requires significantly more injector capacity, Pro Line has designed the manifold to house two 700 lb/hr Billet Atomizer injectors per runner. With the amount of fuel the system will need to burn to make the target horsepower, the team chose to run Fueltech engine management and ignition systems, as they have proven themselves to be reliable in these kinds of applications (more on that in the next installment of the project).
With the top-end all assembled, the engine is ready to receive its ProCharger crank drive system, ProCharger F-3R-136 centrifugal supercharger, and head to the dyno to see what kind of numbers this impressive machine will produce.