There’s no replacement for displacement, and when it comes to cubic inches, you can’t beat a big block. Sure, there have been some amazing things done with small block power, but if you want a ton of torque and horsepower in an engine that isn’t running on the ragged edge, or better yet, a naturally-aspirated pump gas combo, then a big block is the way to go. That’s why the legendary big block Chevy has found its way into any vehicle you can imagine. The key to optimizing a BBC is pairing those big cylinders with heads that can keep up, and to demonstrate the state of the art in out-of-the-box head technology, we recently tested RHS’ brand new line of BBC heads on a textbook example of a big, big block – a 572 cubic inch mill built by DNE Motorsports.
For over 40 years, Racing Head Service (RHS) has been producing high quality cylinder heads for a variety of different engine combinations. Although they have recently moved into the production of engine blocks as well, they haven’t forgotten their roots and continue to advance their head technologies, with new designs and part numbers constantly being developed. Two of the most recent items to come out of their R&D department are the Pro Action and Pro Elite heads for the BBC. While both share a similar foundation, there are some significant differences in the details, and to really break down how they compare, we spoke with Kevin Feeney of RHS.
Pro Elite Heads
The crown jewels of RHS are the Pro Elite line of heads. For big block Chevys, these aluminum heads are great for engines being built for drag racing thanks to their excellent list of features. RHS offers two different sizes of CNC ports on these heads. The first is designed for engines that are 468-540 cubic inches and features a 339cc intake runner.
The other is a 376cc runner design optimized for engines displacing 540-632 cubic inches. Both offer great airflow that can easily reach 400+ cfm on the flow bench. While the temptation to “go big” is hard to resist, it’s important to rely on RHS’ understanding of how intake port volume is dictated by displacement, and not put “too big” of a head on your BBC. Airflow volume, speed, and port-to-port consistency are all equally important.
On the exhaust side, RHS takes the 135cc ports and raises them up half-an-inch. “The exhaust port on the BBC head is the limiting factor. We raise the port up to create a more direct path for the air to travel,” says Feeney. The bolt pattern for the exhaust manifolds or headers remains the same, so no custom headers are needed here.
On the combustion chamber side, these heads feature an unusually thick deck surface that allows angle-milling for higher compression, as well as adding strength. “The extra material works to increase rigidity and gasket sealing, especially in boosted applications,” explained Feeney. Both port sizes feature 121cc combustion chambers and 1.880″ exhaust seats, with the 339cc heads taking a 2.250″ intake valve, and a 2.300″ valve on the 376cc version.
RHS designed these heads to flow big numbers without the need for crazy, exotic parts up top. That is why the Pro Elite heads are designed for stock-style valvetrain components. Even so, the valve angle has been rolled 2° flatter toward the piston. “Rolling the valve angle the way we did gives you a straighter shot for the air,” says Feeney, “It also improves airflow and gives you a better combustion chamber shape.” In keeping with the straightforward valvetrain requirements, the Pro Elite heads also maintain standard angles and layout for the intake manifold mating surfaces, so any stock-style BBC manifold will bolt right up.
RHS did more than simply take a stock, ported casting and use it as a model for the Pro Elite heads. These heads were designed from the ground up to be used on only the most extreme performance engines. “We considered everything,” says Feeney, “One example is the water jacket. For some, it is an after thought in the design process. We thought about it from the beginning and were able to come up with a design that is purpose built to work with the port design. It even improves thermal conductivity.”
We went with Pro Elite heads for our engine build for a couple of reasons. First, they offer the flow capacity that the engine would demand. Second, with the ability to run both stock-style valvetrain components and intake manifolds, this wouldn’t be a crazy high-dollar build, but would still be able to lay down some power. The RHS Pro Elite heads are sold unassembled, and to fill them, they recommend parent company COMP Cams’ components.
Pro Action Heads
RHS also wanted to design a head that would share many of the same great qualities of the Pro Elite heads, but in an affordable as-cast design. Working with their patented Clean Cast Technology, they were able to come up with a head design that rivals many CNC-ported heads. They are offered in both aluminum and cast iron for a number of different applications.
Starting in the foundry where the castings are born, Clean Cast Technology works to improve the surface finish of the ports. According to Feeney, “In an as-cast head, the transitions are the most important part of the design. With a CNC head you can go back and blend it to your liking, but with the cast head, it needs to be perfect from the mold.” Thanks to this special technique, RHS is able to extract every bit of flow possible from an as-cast head.
The Pro Action and Pro Elite heads share a lot of specs with each other. The Pro Action BBC heads are available with either 320cc or 360cc intake runners, with the 320’s set up for 2.250″ intake valves and the larger 360’s taking 2.300″ valves, just like their CNC siblings. Both Pro Action heads have 1.880″ exhaust valve seats, and 119cc combustion chambers. They’re also both available in hydraulic or mechanical roller versions, capable of .600″ or .750″ lift, respectively.
While the Pro Elite does offer larger runners and more flow for extreme builds, the Pro Action is a great head those looking for cost-effective performance right out of the box. RHS offers the Pro Action heads in both assembled and bare versions, so incorporating these heads into your project is as easy as ordering a single part number. The assembled Pro Action heads are filled with quality COMP Cams valvetrain components.
Just like the Pro Elite heads, with the Pro Action you get the extra thick deck surface, the optimal water jacket design, and the raised exhaust ports. This makes them ideal for a number of different applications from stock-style bracket classes to higher end heads-up racing, and of course street performance.
One of the most common things we see when someone buys an assembled head is that they still end up changing out something like valve springs or valves to fit their particular build. This ends up costing extra money and adds another hassle. What you may not know is that when you order assembled heads from RHS, you can complete the heads with your choice of any valvetrain found in the COMP catalog. This can save both money and time by getting the exact parts you want right from the start – just call up RHS and tell them what you want.
Putting it Together
While the flow bench is a valuable tool for understanding how a cylinder head performs, there’s no better way to test a pair than to build an engine to slip underneath, and dyno the result. Using RHS’ Pro Elite heads, we did just that, but we couldn’t have done it alone, so we got in touch with DNE Motorsports and Westech to lend a hand in building one nasty BBC and testing the final product.
DNE Motorsports builds high performance engines for a number of different worlds, from drag racing to power boats and hot street cars. They rely on their years of performance engine building experience to come up with proven combinations that make serious power.
Building the Short Block
If an engine’s power is in the heads, then the strength is in the short block. For this build, we knew that we’d be surpassing the 800 horsepower mark, and would require a stout bottom end to keep it all together. The foundation started with a Dart Big M Sportsman Block. This iron alloy block has plenty of deck thickness and priority main oiling already built in. It would serve as the perfect base for this engine.
Here’s the overview of what went into our BBC:
Block: Dart Big M, 4.125″ Bore, 9.80 Deck Height
Crankshaft: SCAT 4340, 4.375″ Stroke
Pistons: CP Pistons
Connecting Rods: SCAT H-beam
Rings: Perfect Circle Performance
Camshaft: COMP Cams – Custom Ground
Timing Chain: COMP Cams Ultimate Billet Timing Set
Damper: ATI Super Damper
Oil Pan: Dan Olson
Heads: RHS Pro Elite 376cc
Valves: Manley 2.300 Intake/1.880 Exhaust
Springs: COMP Cams Elite Race Valve Springs
Intake: Edelbrock Super Victor, Ported by Wilson Manifolds
Rockers: COMP Cams Pro Magnum
Carburetor: Holley 1050 Dominator by David Cook of DC Carburetors
The camshaft chosen for this build was a COMP Cams custom grind. This mechanical roller cam measured in at .473″ max lift on the intake and 471″ on the exhaust, with a duration of 270/277 measured at .050″. “We do custom cams for every application,” says Dave Ebbert of DNE Motorsports. “We try to match the cam profile and cam series to each engine combo. We look at bore, stroke, RPM range, and what the engine is capable of. Then decide where we want the peak torque to be.” For this engine, Ebbert went with the DSP series on the intake lobe, which is a relatively ‘fast’ profile that works well in low-ratio, high RPM applications or (as in our case) with a lower engine speed that can use a faster lobe. On the exhaust, he chose a UBA series lobe, which is similar to the UB design (which itself is based on COMP’s NASCAR-style flat tappet designs and optimized to take advantage of the additional tappet velocity allowed by roller lifters) but is faster off the seat, which improves performance in relatively slow-turning engines like ours. With the cam installed, the rest of the internal components soon followed.
Completing these 4.560-bore pistons was a 1/16″-1/16″-3/16″ ring package from Perfect Circle Performance. The top compression ring is ductile iron, a cast tapered hook grove (THG) design was used for the second ring, and a light tension oil ring completed the set.
COMP Cams also provided an Ultimate Billet timing set and their two piece billet aluminum timing cover so the cam could be swapped without removing the oil pan every time. A Melling oil pump was installed just before a Dan Olson kickout oil pan was attached to the bottom. Cometic Gaskets were used throughout the build as well.
Topping it Off
From there, Ebbert moved to the top end of the build. DNE started off by testing a few different valve designs on the flow bench to see which ones the RHS Pro Elite heads worked best with. “What we came up with was that these ports liked the under-head radius valves throughout the lift range,” said Ebbert.
The Manley valves ultimately chosen were 11/32″ stem diameter, with the 2.300″ intake valves carrying a 12° by 3/8″ under-head angle radius and an overall length of 5.610″. The 1.880″ exhaust valves measure 5.522″ long, and featured a 25° by 3/8″ under-head angle radius.
A set of COMP Cams Elite Race valve springs (part number 26115) keep the valves under control. These were set up with a seat pressure of 240 pounds, open pressure of 685 pounds at .780 lift, and a 572 pounds-per-inch spring rate. They are capped by COMP titanium retainers, part number 732.
The intake manifold chosen for this build was an Edelbrock Super Victor, with porting and plenum work provided by Wilson Manifolds. “They do a really nice job of porting and blending the entire manifold,” explained Ebbert. “That helps with torque output and fuel distribution.”
Up top is an 1150 cfm Holley Dominator 2-circuit carb with power valves. David Cook of DC Carburetors did the final tweaking before it was bolted on. “I’ve known David for 15 years, and he is one of the few I trust to touch my own personal carbs,” added Ebbert.
To see how our Pro Elite-headed big block performed, we looked to Westech Performance Group, the go-to guys for west coast dyno testing. After warming up the brand-new 572ci mill on their SuperFlow engine dyno, the pulls began in earnest, and we weren’t disappointed.
When they say that there’s 1,000 horsepower potential from the Pro Elite for the BBC, we believe them – our best result was an amazing 883 horsepower and 758 foot-pounds of torque, on pump gas no less, and with no need for exotic valvetrain components to let the engine spin to the moon. If you need proof that RHS isn’t messing around with their Pro Elite cylinder heads, look no further than this. For more build photos, be sure to visit our complete gallery.