As you can see, installing rocker arms with a ratio higher than stock will lift the valve higher off of the seat, which can have a positive effect on engine performance. So if you want a higher lift camshaft without having to replace the cam, bolting on a set of rocker arms with higher ratio can give you the lift you want. Remember, however, that many Mopar cylinder head castings need to be machined so that the valve retainer doesn't interfere with the top of the valveguide, so always consider that factor before swapping rocker arms. The valvespring needs to be considered as well when installing higher ratio rocker arms, as more valve lift will bring the spring closer to coil bind.
While higher valve lift can mean more power, we consider duration a more important factor when it comes to performance, and higher ratio rocker arms do not increase the duration of the cam. The cam should always be matched well to the rocker ratio, giving the proper valve lift and duration for the application the engine will be used for, and for this we recommend speaking with the cam manufacturer directly through resources such as Comp's cam help line. Speaking to one of the professionals will ensure that your combination of cam, pushrods, rockers, and valvesprings is compatible and optimizes the capabilities of your engine.
Which Rocker Arms are Right for my Engine?
Choosing the proper rocker arm can be a matter of preference to an extent, but has more to do with the camshaft and valvespring than it does with the engine as a whole. The higher the lift of the cam, the higher the valvespring pressure needs to be, in order to keep the valves in control at high rpm, which equates to more load on the rocker arm. In fact, as the pushrod applies pressure to one side of the rocker and the spring applies pressure to the other side, the cumulative effect tries to break the rocker arm in half, kind of like you'd break a stick in half over your leg.
Stud mounted rocker arms like found on the Magnum series of small-blocks suffer the additional strain of deflection caused by the forces of the valvespring and pushrod. Guide plates for the pushrods and a stud girdle for the rockers can help alleviate this issue, but the best way to solve the problem is to convert to shaft mounted rocker arms. Fortunately, Magnum engine enthusiasts can benefit from RHS's line of cylinder heads which not only offer the option of shaft mounted rockers, but also have either the Magnum or LA intake bolt pattern. Luckily, all other popular Mopar engines have the stronger, more stable shaft mounted rocker systems.
Engines with mild, hydraulic, flat-tappet camshafts up to around .500-inch lift can survive with factory stamped steel shaft mounted rocker arms, but can always benefit from the higher accuracy of quality aftermarket rockers. And if you have a solid lifter camshaft or roller cam in your engine, you'd better consider a rocker arm upgrade as mandatory. Additionally, if your engine is topped with aftermarket cylinder heads, the offset of the rocker arm needs to be matched appropriately as many high-performance cylinder heads have wider ports than factory heads, and sometimes the valve location is modified.
Increasing cam lift significantly over .500 inch, or installing a roller cam in your engine, means you'll need an aftermarket set of rockers. There are a good variety of moderately priced aftermarket rockers for Mopar engines on the market today, some made from aluminum, others from steel, and nearly all feature a roller tip for improved valvetrain geometry. The roller tip only marginally reduces friction and doesn't improve performance so much as it allows the rocker to be made from lighter material. We've had good luck with moderately priced aftermarket rocker arms from many companies including Comp Cams and Crane, but for engines that are designed for maximum power and endurance, you'll want the best quality rocker arms available.
Premium shaft mounted rocker arms not only contain a roller tip where the rocker engages the valve, but also needle bearings where the rocker rotates around the shaft. These bearings keep the rocker arm securely in place, and can take a higher load than rocker arms without needle bearings. Consider Harland-Sharp, Comp, or T & D Machine for premium rocker arms, and for the ultimate valvetrain stability, Jesel makes rocker arms for most Mopar applications that utilize individual shafts for each pair of rockers. Designed for maximum endurance and stability, the Jesel rockers are nice, but come at a price. The cylinder head must have some special machine work performed to accommodate the Jesel rockers, which can be cost prohibitive for the average engine build.
So, remember, aftermarket rocker arms can be a great upgrade to your Mopar engine and should be considered mandatory when utilizing a solid lifter camshaft, roller camshaft, or even a hydraulic cam if over .500 inch lift. We encourage you to shop around, as many of our advertisers manufacture great rocker arm systems for Mopar engines, and all are easy to install in a day or weekend. The right rockers can not only make more power, but add reliability to your engine as well. So keep your Mopar rockin' with a new set of roller rockers!
Aftermarket roller-tipped rocker arms like the Ultra-Pro Magnum series from Comp offer added valvetrain stability while keeping rocker arm weight low. These rockers are economically priced, and we've used them with good success in conjunction with solid lifter camshafts.
Most Mopar engines came equipped...
Most Mopar engines came equipped with 1.5 ratio rocker arms, and can benefit from higher ratio rockers to gain valve lift. Remember that the additional ratio increases valve lift, and will compress the valvespring more, which could lead to coil bind. All of the critical dimensions such as retainer to guide clearance should be checked before installing rocker arms with a higher ratio.
Premium roller rocker arms...
Premium roller rocker arms offer roller bearings where the rocker rides on the shaft as well as a roller tip. The roller bearings will endure higher loads, while reducing internal friction as well. For maximum performance, especially when using roller cams and stiff springs, high quality aftermarket rockers should be considered mandatory.
Rocker arm offset is also...
Rocker arm offset is also an important factor when choosing the right rockers for your engine. You can clearly see that the Indy rockers (right) have more offset on the intake side so that the pushrod clears the larger intake port. Your cylinder head manufacturer will include rocker offset information with your new heads.
Most shaft mounted rocker...
Most shaft mounted rocker failures don't involve the rockers themselves, but the attaching hardware. This failure was caused by not enough thread engagement of the bolt holding the rocker shaft to the cylinder head. No matter how good the parts, proper installation, adjustment, and maintenance are key when it comes to engine durability.