Review: Comp Cams - More Power to the Rat! Project Potent Rodent

Dec. 01, 2000 By Shawn Spickler
For the ultimate stump pulling power, you can't beat the mind-numbing torque and horsepower of the big block Chevy also known as the a "Rat" engine (term GM used). These engines are very capable of producing gobbs of power depending on how they're built. In stock form, most big blocks are really low-keyed in terms of power. Now, we're not talking about the high-horsepower 70 Chevelle 454 SS engine (with 450 HP) or similar early 70's muscle cars. We're talking about the run of the mill 454 car/truck engines that were produced in the late 70's, 80's and early 90's. When attached to a dyno, these engines aren't really a powerhouse in terms of horsepower. To prove this we actually put project Potent Rodent on the chassis dyno and were devastated what the actual numbers were the engine was really producing. The stock GM remanufactured 454 engine only produced 190 hp and 335 lbs of torque at the rear wheels. Keep in mind the rear wheel horsepower and torque will always be much less compared to the flywheel since the power has to travel through the transmission, t-case and axle which will always reduce hp/torque figures. Granted the torque isn't bad but you would think a 454 would produce more than 200 hp.
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Hope those straps hold!
Here's the K5 on the Dyno. This was done before the new cam was installed. We'll be running another dyno shortly to get the "after" results.

After the run, we were really disappointed with the power of the stock 454. Only 190 HP. A new cam is a must if you want more power. Notice the small tires on the rear. The large Swampers wouldn't fit on the dyno!

So… how does one get more power out a weak factory engine? One key improvement is the camshaft and associated valve train. Big-block Chevys like to breathe, and a healthy camshaft is essential to accomplishing that goal. That doesn't imply that a huge camshaft with 320 degrees of duration and .700-in. of lift are required in all cases, but most big-blocks will respond favorably to slightly more aggressive valve timing than is used with some other types of engines.

For our camshaft needs, we turned to Comp Cams. Comp Cams is the leader in camshaft design and technology. For a huge selection of camshafts and valve-related products, you can't beat this company. Comp Cams can hook you with the right cam and related valve train that's specifically designed for your application. This is an important step since you never want to run a cam that was never designed for your heads or engine. All it takes is a simple call to Comp Cams tech support and they'll assist for whatever your needs might be. Comp Cams has been around for over 25 years and will continue to be there in the future to stand behind their products. After looking through Comp's catalog, we can say that Comp Cams has everything you need to do the job right and then some!

Camshaft

By doing a cam change, you're guaranteed more power compared to a stock setup. We went a step further and got the Xtreme Energy hydraulic roller cam from Comp. The roller cam will benefit you buy reducing the friction on the cam lobes and lifters and can also tolerate much faster opening and closing rates. The lifters actually have steel rollers that ride on the cam lobes. The camshaft is made for these roller lifters and is made of a higher grade steel that is much stronger than your standard cast camshaft. The hydraulic roller cam has the best of both worlds. It increases power but still keeps the beast drivable on the street and trail. The Xtreme cam is the newest series of hydraulic roller cams. They are designed to take advantage of the latest improvements in valve train components and the latest developments in camshaft design. Their aggressive lobe design produces better throttle response and top end horsepower than other cams with the same duration, while delivering increased engine vacuum.

XR276HR
Duration:
Intake: 276
Exhaust: 282
Duration @ .050"
Intake: 224
Exhaust: 230
Lift: .510 (Intake and Exhaust)
Lobe Separation Angle: 110

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Cam specs.

The Comp Xtreme Energy 276 roller cam.

  Roller Lifters

The roller lifters are necessary when running a roller cam. Comp Cams Pro Magnum hydraulic roller lifters are specifically designed to perform at higher engine speeds. When engines are equipped with a hydraulic camshaft, high rpm is limited by the improper position of the internal piston as the lifter inevitably "pumps up". This improper location results in open valves and therefore leads to lost power or sometimes even engine failure. Roller lifters not only reduce friction and wear, they allow for much more aggressive lift rates. A link bar is required to prevent the lifters from rotating the their bores.

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The roller lifters ride on the cam and have several advantages over standard non-roller lifters.

Springs

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These Comp Magnum dual springs match the cam specs. This is critical that all components match.

Valve springs are one of the most critical and most over-looked components in your engine. They must be matched to your cam in order for the engine to reach its full potential. It does absolutely no good to install a cam that will rev to 8000, if you don't have the correct springs. The use of the wrong valve springs is one of the most common causes of engine failure. Another is the incorrect installation of the valve springs. Each Comp spring is CNC coiled, stress relieved, ground, shot-peened and heat set. Comp designs their valve springs for specific applications because there is no such thing as a one-size-fits-all valve spring. Valve train components are matched by testing the dynamic interactions between them using a cycle tester, strain gages, load cells, laser displacement transducers, high-speed videos and more. This allows Comp to assemble the best combination of parts for an application by reducing the stresses and increasing the life of each part in the system.

  Rocker Arms

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These Comp Magnum roller rockers are made from chromemoly and will benefit any application by actually giving more lift since they don't flex like others. They also offer less friction due to the roller design.

COMP Cams Magnum Roller Rockers are the ultimate street rocker setup. They will help your engine make more power and last longer. Magnum Roller Rocker Arms are very strong. They're made from 8620 chromemoly steel. This makes them stronger than die cast aluminum or stamped steel rockers. This superior material, along with the Magnum's super stiff design, assures maximum lift because this rocker arm will not flex. The rockers are also accurate. You can't get maximum horsepower from your engine if your rocker ratio is off. Some rocker arms can be .040" short on lift. The Magnum Rockers are super accurate and check dead on every time. According to Comp, the Magnum Roller Rockers can make between 15 and 30 horsepower over other rockers! Why? The secret is that not only does the roller tip reduce friction, the Magnum Rockers incredibly stiff design and super accurate ratios yield more effective valve lift. The roller tip design reduces friction by not scrubbing the valve end or pushing the valve stem hard against the valve guide. This in conjunction with super strong design of the rocker makes for a simple, bulletproof, and cost effective combination. Magnum Roller Rockers can be used with almost any hydraulic or solid cam where open spring where open spring pressures do not exceed 350 lbs.

Pushrods

Comp Cams High Energy pushrods are a good choice when building an engine. High Energy pushrods are manufactured to meet or exceed all original equipment specifications. The will mate perfectly with High Energy or Magnum rockers. These pushrods will stand up to higher spring pressures and the associated stresses of a high performance engine. All pushrods are Heat Treated to be compatible with guide plates. It is always a good idea to replace your pushrods when you install new rockers. Pushrods and rockers wear together much like cam and lifters. Even though the pushrods may not show any wear, installing new rockers on old pushrods can result in premature failure.

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The pushrods should be replaced when replacing the cam, lifters, and rockers. These are thicker than our 5/16 rods.

Timing Chain

Any time you upgrade the cam, you might as well replace the existing chain, which is probably worn and stretched. We used Comp Cams Hi-Tech Roller Race Chain. The features on this double roller chain include a triple index gear, oversized rollers and it's dynamically balanced.

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A Comp timing chain is a must for any cam.

Valve Locks

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New valve locks and retainers are installed with the new springs. Anytime you go with high performance springs, you should always replace the locks and retainers with something stronger.

New valve locks were also acquired from Comp since we weren't sure what the condition of the old valve locks were. Even though the locks are a small part of the valvetrain, they should never be over looked when upgrading your springs. Most people believe that the tang inside a valve lock is what actually holds the valve spring retainer and spring in place while the engine is running. This is not the case. The cross- section of material in the tang is not strong enough to withstand today's open spring loads of 1000 pounds or more! The sole purpose of the tang is to temporarily locate the lock, retainer, and spring relative to the valve until the taper of the retainer can nest around the outside surface of the lock. This creates a "collet" effect that binds the two together. The more spring force exerted on the retainer (as the valve opens), the more force applied by the "collet" effect to keep the retainer and lock in place. It is also important to make sure the valve locks match the valve size. All locks should be checked prior to final installation to make sure that they are the correct size.

Retainers

New valve springs with larger diameters or multiple springs require new retainers to handle the higher pressures developed by the springs. COMP Cams steel retainers are the solution. The steel retainers are precision machined from 4140 chromemoly and finished in black oxide. These precision retainers are specifically designed for positive location when combined with COMP Cams valve springs.

Bronze Gear?

Most brands of roller cams require a bronze gear to be installed on your distributor. This is due to the fact that a stock cast iron gear is not compatible with a steel roller camshaft. The downside to going to a bronze gear is it won't last long and is not suitable for a daily street driver. Fortunately, Comp makes most of their street roller cams a special steel so it's compatible with the stock cast iron distributor gear. A special bronze gear is not required for our cam.

Tools:

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For any cam swap, this tool is a must. This cam installation handle makes it easier to slide the camshaft in and prevents damage to cam bearings. Extra cam bolts are stored in the handle.

There's many tools you can get from Comp Cams to aid in the installation of the new cam and related products.

One essential tool is the cam shaft handle. This bolts to the front of the camshaft and helps the removal and installation process. Trust us, we've tried other ways to remove and install cams, and the bearings will always suffer if a cam handle isn't used.

The harmonic balancer installer is another important tool to have. Again, take our word since we've tried the improper way to do this. The improper way involves using a standard bolt to put pressure on the harmonic balancer so it slides on the crankshaft. Then after you break the bolt, you have to use an easy-out which breaks also. Then a special drill bit must be used to remove both easy-out and bolt which takes all day long. The treads will then have to be re-tapped. Definitely, not a fun process and yes, this has happened to us! COMP Cams harmonic installer makes it much easier and saves the crank from any damage. There's an adapter (many different sizes to choose from) that screws in your crank. A larger threaded shaft attaches to the adapter. The balancer is then pressed on with a large nut and bearing. The harmonic balancer installer also is used to install the crank gear of the timing chain.

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The harmonic balancer installation tool is a must to avoid any damage to the crankshaft.

This sportsman degree kit comes with everything you need to degree the cam plus it comes with a crankshaft socket.

When you install a high performance camshaft, you can do it one of two ways- just stick it in the engine and button everything back up, or you can do it the right way. Without exception, the right way means degreeing it in (also called phasing the camshaft) to assure that valve timing events occur at precisely the right time with respect to the crankshaft position. The degreeing-in operation is simply a matter of checking an engine's real life valve opening and closing timing against the figures on the spec card that accompanies each camshaft. It is accomplished by mounting a degree wheel on the front of the crankshaft and utilizing a dial indicator to check cam lobe lift. Degreeing the cam isn't always performed on most cam installations but we felt it was an important step. To do this, we used Comps Sportsman Degree kit which includes a 9" degree wheel, head off degreeing fixture, 0-1" dial indicator, TDC stop plates, pointer and a crankshaft socket. The crankshaft socket is used often since the crank has to be turned many times during the build.

Installation

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We're also changing the heads and a few other things so it was best to remove the engine. Normally, the cam can be installed with the engine in.

To install a cam, it's not that difficult. It does require some disassembly of the engine so a few common tools (and common sense) are required. Since we're also installing a stroker crank, the engine has been removed from the vehicle so it's actually easier to install the cam. You can install a cam with the engine in the vehicle. Great care must be taken when removing and installing the new cam. The soft cam bearings will easily be damaged if a cam handle and great care isn't used. Basically, to get to the cam, you must remove the distributor, intake manifold, valve covers, water pump, harmonic balancer, and timing cover. If a cam is installed with the engine in the vehicle, the radiator and possibly the front grill will have to be removed so the cam can be installed. Comp has excellent instructions which, are all available on their web site.

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The old camshaft is removed from the block.

After the necessary parts are taken off, the rockers and pushrods are then removed. We're using new lifters, push rods and rocker arms, but if you're re-using the existing rods and rockers, you should always number the pushrods and rockers so they go back in the same place. After the rockers and pushrods are removed, the lifters are next. Usually, you want to buy new lifters with the cam so there's no need to number the lifters since you're tossing the old ones. The timing chain and gears are then removed. The crank gear might be difficult but it should come off with a gear puller. We managed to break our crank gear in the process. Finally, the old cam is carefully extracted with Comp's cam handle. Be extra careful not to nick the cam bearings.

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The new camshaft is installed in the 454 block. Great care is taken not to nick the cam bearings.

For complete detailed instructions from Comp Cams, check out their web site or these detailed instructions below. With Comp's detailed instructions, we felt it wasn't necessary to re-write the book on the cam install. Comp Cams has excellent instructional material on everything that deals with an engine. They also offer video tapes not to mention, their excellent tech support is just a phone call away. Cam Instructions 1
Cam Instructions 2
Cam Instructions 3
Cam Instructions 4

With the old cam removed, the new cam can now be installed. Usually, assembly lube is used on the lobes but with a roller cam, you just use motor oil. Again, the cam handle is used and it's carefully installed in the block. The new timing chain and gears are installed next followed by the new roller lifters. The lifter rollers are cleaned and oiled before installation. Since our block doesn't have the heads mounted yet, we used our Sportsman degree kit to check the timing of the cam. For more information on this, see the complete degree instructions here: Degree Instructions 1
Degree Instructions 2

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Setting up the Sportsman degree kit.

After the cam is installed and degreed, the new Comp springs are installed on the heads. Using Comps instructions, the springs were installed properly using a spring height micrometer. This will help you determine what shims need to be installed with each spring. For more information on spring installation, see the link below.

Valve spring instructions

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The new roller lifters. Notice the brace that keeps the lifters from turning.

After the valve springs are finished, the piston to valve clearance was checked. The clearance was checked using some clay. This ensures there is no interferance between the valves and pistons at full lift. Everything looked good so the heads were finally bolted on. Fel Pro head gaskets are used to seal the heads to the block. The new pushrods and roller rockers can then be installed. Since our heads were made way back in the early 70's, we also opted to replace the old rocker studs just to make sure all studs are adequate for the job. Each pushrod has to be adjusted in a certain sequence. Each rocker arm is adjusted until all lash is removed. It helps to apply some oil on your fingers and spin the pushrod until you can't spin it any longer (with a light pressure on the fingers). This is called zero lash. After you find zero lash, tighten the rocker 1/2 a turn. The timing cover is installed followed by the harmonic balancer which, is pressed on with Comps harmonic balancer installer. After the valve train is finished, the other components are installed and the engine is installed.

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The roller rocker arms are installed.
Performance

Stay tuned for another dyno on this setup. With Comp Cams valvetrain products inside the rat motor, we feel confident that it will be screamer. A PC Dyno program was ran with the same specs as this engine and it showed well over 500hp and over 600lbs of torque! Granted, thats at the flywheel but it should still be impressive on the chassis dyno. The beauty of this setup is it's still driveable on the street and trail with no side affects such as lack of vacuum or a rough lopey idle. If you're in the market for some added performance, give Comp Cams a call and see what they can do for you.

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