The Power Hidden Within Your ZZ4 Engine

[CPG Marketing]

COMP Cams Introduces Five Great Options For Waking Up Your Chevrolet ZZ4 Crate Engine

First, let's begin by giving props where they are due. Chevrolet did a great job when it introduced the ZZ4 crate motor. It is based on Chevy’s classic V8 small block, and the motor is about the most cost-effective way to get a new V8 into your street rod, truck, race car or almost anything else you have sitting around. As a result, the ZZ4 has been one of the best-selling crate motors ever.





But when you evaluate its performance, the ZZ4 can be a bit lacking when it comes to power production. Although it is rated for 350 horsepower (hp), the usual numbers found in dyno testing show the engine off its advertised numbers by about 8 hp. And let's face it, while it is enough to get you to the grocery store and back, 340 hp isn't much to get excited about these days.

That's why engineers at COMP Cams recently spent several months and countless dyno hours thrashing a ZZ4 of their own to see just what it was capable of. The idea was to give their customers who already have ZZ4 or similar engines a way to have more fun without spending a lot more money.

“We didn’t set out to do anything from a marketing standpoint,” COMP’s Director of Marketing Chris Douglas explains. “We just let our R&D guys go at it. We said, OK, based off what we have to work with here and sticking to a reasonable budget, what can we come up with to really improve this motor?”

“And after doing a lot of research and trying a lot of different parts - I mean this project went on for the better part of three months - we learned a lot of things. We learned where the choke points for making power in this engine were and how to overcome them. And we came up with five different packages of components that will really light up this engine. Which one you choose depends on how much more power you want and your budget.”

The result is five power-tuned part packages now being offered for the ZZ4. Not only are the parts sourced to fit this engine, but COMP also tells you how much horsepower each package is worth so you will know what you are getting. All dyno testing for these packages was performed on a brand-new ZZ4 fitted with a Demon 650 cfm carburetor and 1 5/8-inch primary tube headers. Power in stock form for this combination turned out to be 344 hp at 5,300 rpm and 390 lb./ft. at 4,300 rpm. The Stage 1 package utilized a factory dual-plane manifold while Stages 2 through 5 were upgraded with an aftermarket dual-plane intake in order to provide sufficient air flow.

Stage 1 The Stage 1 package includes a set of Pro Magnum Rocker Arms complete with polylocks and a set of one-piece chromemoly Magnum Pushrods with 0.080” wall thickness. The rocker arms are a light-weight, full-roller design constructed from steel that not only reduces resistance in the valve train but also increases stiffness and durability. Likewise, the pushrods are much stiffer and stronger units than the stock units. Incredibly, just adding these two components to your ZZ4 can add 16 hp to your engine - quite impressive. That not only brings the ZZ4’s total power production up to 360 hp, but Douglas says the Stage 1 upgrade also creates the perfect foundation for getting the most out of Stages 2 through 5 if you choose to add any of them later.



”That's the great thing about it,” he says. “If you just have enough in your budget for Stage 1, you can purchase that now and go ahead and install it. Then, if you want even more power down the road, you can purchase another stage and it only adds to what you've got. You do not have to throw out any components from Stage 1.”

“Stage 1 is definitely something a guy could install on a Saturday night in his shop. It doesn’t require any special tools or even a whole lot of mechanical knowledge. Even if you do not add anything later on, I think these upgrades are something that should be done to any ZZ4. The pushrods that arrive in the crate engine are really just cheap pushrods. They use press-fit tips, and in our testing we’ve found them to be quite flexible. Even our stock replacement pushrods are stiffer than what arrives in this crate motor, so our Magnum Pushrods are a real improvement.”

Seeing the advantages of an upgraded pushrod versus a well-machined roller rocker arm may be more difficult, but the usefulness is definitely there. A pushrod that isn't stiff enough for the application will collapse when the cam tries to open the valve. This not only delays the timing for valve opening, but when the pushrod springs back into shape at maximum valve lift, it can lead to a valve float. That is why switching out for a set of well-designed rocker arms and pushrods can make a 16 hp difference in an engine without even touching the camshaft.

Stages 2 and 3
Stages 2 and 3 both add a camshaft, a set of springs and a matching set of spring retainers. Stage 2 uses a Thumpr Hydraulic Roller Camshaft, a set of COMP’s Beehive Valve Springs and your choice of either steel or titanium retainers. The Thumpr Cam is rated for 227/241 degrees of duration at 0.050”, lifts the valves 0.518 and 0.503 inches and is at its best between 1,900 and 5,600 rpm. Stage 2 is good for an increase of 55 hp and 20 lb./ft. of torque (if you have already installed Stage 1). That means total power is now upped to 399 hp and 410 lb./ft. of torque!





COMP’s Sales Manager Rick Sparks says one of the ZZ4’s weaknesses actually made it possible to use much larger cams without having to resort to pulling the pistons and cutting larger valve pockets. “The pistons on the ZZ4 stay way down in the hole, even at TDC,” he says. “So even when running the larger Thumpr Cams, piston to valve clearance doesn’t become an issue.”

Stage 3 uses the same spring and retainer options but switches out the cam for a high-end Mutha Thumpr Hydraulic Roller Camshaft. The Mutha Thumpr ups the ante even more with increased duration (235/249 at 0.050), lift (0.528/0.514 inches) and attitude. Although the Thumpr line of camshafts produces effective power, they really make their name with the sound they help an engine produce. The mild cam that comes stock in the ZZ4 makes the engine sound pedestrian, but with a Thumpr in place, the ZZ4 has a low-rpm rumble that is unmistakable and slightly menacing. That makes it perfect for those Saturday night cruise-ins where “show” is as important as “go,” but it also provides performance to back up that unique sound. The Stage 3 package adds 64 hp to blow past the 400 hp barrier with a total of 408.

Stages 4 and 5
By adding a set of cylinder heads to the mix, stages 4 and 5 switch things up again. The Stage 4 package basically uses the cam and springs from the Stage 2 upgrade kit and adds a set of RHSª Pro Action Cylinder Heads. These 23-degree heads feature a 180cc intake runner for excellent throttle response and 64cc combustion chambers to provide a pump-gas friendly compression ratio when paired with the ZZ4’s flat top pistons.



Stage 5 uses the same RHS cylinder head but upgrades the cam to the Mutha Thumpr last seen in Stage 3. Pro Action Cylinder Heads arrive already assembled, and COMP can even throw in the correct gaskets. All you have to do is bolt everything in its proper place. Finally, these Pro Action Cylinder Heads are available in either aluminum for light weight and a great look, or cast iron if you are on a tighter budget. The choice is up to you, but power production for both is virtually the same.

And speaking of power, the good news is that the Stage 4 upgrade bumps up the power a whopping 83 hp while pushing the torque up another 36 lb./ft. That brings total engine output to 427 hp and 426 lb./ft. of torque! Going all the way with the Stage 5 upgrade is worth 92 hp and final engine numbers of 436/426!

Of course, a cylinder head swap, while certainly doable for most weekend mechanics, is a serious upgrade, but Sparks says it is necessary to get the most out of the ZZ4. “Those stock heads really are a limiting factor for that engine,” he says. “What we ran into with these heads on the test is once the camshaft duration got up around 230 to 240 degrees at 0.050”, power just plateaued. We ran up against a wall because the heads wouldn't flow any more. It wasn't a good combination. We tried putting more camshaft to it and several other things, but those heads just wouldn't let it make any more power.”





“The only way past that was to improve the cylinder heads. Once we put the RHS Pro Action Cylinder Heads on there, the numbers took off again. That is why we are offering our packages with the cylinder heads because we know that some guys are going to want those power numbers.”

Interestingly, the stock hydraulic lifters were kept with all five power packages. Douglas says they could have forced customers to purchase the lifters as part of one of the sets, but it isn’t absolutely necessary and would make the cost higher. An upgraded set of hydraulic lifters is certainly an option, but you aren’t forced to buy them with these packages.

“The factory lifters in this engine are pretty good. I can tell you that we did some testing with them and they turn some pretty good rpms. We chose to replace the springs and not the lifters because the greatest problem for valve control here is the weak valve springs and not hydraulic lifters pumping up like you might think. By adding the Beehive Valve Springs, you cut a lot of weight. That keeps you from having to put a lot of seat pressure on the thing while still maintaining the valve control. Using the Beehive Valve Springs helps the stock lifters perform a lot better.”

So far, these engineered power packages have been met with great acceptance among both the cruise-in crowd and the power fanatics, and Douglas says they will grow in popularity as more people realize they are available and easy to install.

“We’ve gotten to the point where it is just not really cool to have a crate engine in your street rod or hot rod, he says. “Plus, Chevrolet has sold so many of the ZZ4 crate engines, that if you show up with one at a car show or the drag strip, you are going to be one of many with that engine. Using one of these power packages really sets you apart. It gives you more of a custom engine and nobody can deny that because it sounds so good - definitely not like a stock ZZ4. Stages 2 through 4 really set you apart from the crowd, not just from a performance standpoint but also because of the sound.”

Once you reach Stage 4 or 5 and decide that you want to push the power limits further, the sky is basically the limit. Douglas says they could have made other packages that added nitrous or other options to the mix, but they decided a more custom touch is necessary at this level.

“Once you get beyond Stage 5, you really start getting into some custom stuff. It can go a thousand directions from there depending on your taste and what you are trying to achieve. I’m not sure we would ever be able to work out a Stage 6 that we would be comfortable selling to anyone like Stages 1 though 5. Instead, if someone gets to Stage 5 and decides that still isn’t enough or they want to try something a little bit different, I would recommend they give us a call and we will custom design a Stage 6 specifically for them.”

“Just give us a call on our CAM HELP line (1-800-999-0853). We have upward of 15 technicians on the phone every day. And that’s what they are trained to do - make something that works just for you.”