Chrysler invested millions of dollars and spent thousands of dyno hours designing and validating the Gen III Hemi valvetrain. And in stock form, it's an excellent design that'll go thousands of miles with total reliability. But things change when you start messing with the factory formula. While the stock 5.7's 340 and 6.1's 425hp ratings are nothing to be ashamed of, they only scratch the surface of the new Hemi's potential.
At Superior Automotive, Joe Jill and his crew have a steady customer base of Gen III Hemi owners looking for extra punch. Some just want their Ram pickups, Chargers, 300s, Magnums, and Challengers to scoot a little quicker with a simple cam swap, while others are paying big money for supercharger installations, nitrous systems, 440-inch stroker kits, and are really pushing the boundaries. What both camps have in common is the discovery that the Gen III Hemi needs a little help in the valvetrain and cylinder head department to meet expectations.
Let's have a look as Superior's Fred Simpson shows off some new developments that clear the way for even more Hemi horsepower.
The stock 5.7/6.1 parts are...
The stock 5.7/6.1 parts are high quality, but the beehive valvesprings can fail when teamed with hotter-than-stock aftermarket cam profiles. The 5.7's factory installed springs are rated at a healthy 260 pounds (SRT8 is slightly more). But both coil bind at about 0.550-inch lift and cannot be teamed with higher lift cams.
The pen points to the stock...
The pen points to the stock 5.7 and 6.1 triple bead valve lock configuration. Stiffer aftermarket valvesprings set up a pinch load on the bottom receiver groove in the valve stem. This can cause separation and a dropped valve. Another flaw is encountered during valve float where uncontrolled movement between the stock valve stem, keepers, and retainer rolls the grooves in the stem. Fred says the problem can range from the creation of nuisance burrs to all out removal of the grooves in the valve stem and is a disaster in the making.
This premium quality aftermarket...
This premium quality aftermarket valvespring broke after 13,000 miles in a customer's SRT8. Fred says, "Stock Chrysler beehive springs can break within a few days or months after a hotter cam is installed. Good aftermarket springs go longer, but also eventually fail."
Some valvespring failures...
Some valvespring failures hang the valve open until a piston strike bends the stem or breaks off the head, which rattles around inside the cylinder and destroys the engine. Another common failure causes the spring to collapse into itself and become solid. This bends the pushrod and can even snap the rocker shaft (as shown here).
Working with Manley Performance,...
Working with Manley Performance, Joe came up with a proprietary valve design that solves the problem. The trick valves feature the same overall length as stock Gen III Hemi valves (4.950-inch intake and 4.925-inch exhaust), but are machined with slightly lower valve lock grooves. This moves the retainer position down, away from the bottom of the rocker arm and opens the door for larger diameter straight-type valvesprings. The pen points to the end of the custom Superior/Manley valve. Also note the use of single groove locks, which give greater clamping force and eliminates the stem galling problem encountered with stock triple bead configuration seen on left.
Here is a picture of what...
Here is a picture of what not to do to get the needed rocker-to-retainer clearance. Because Chrysler used net-shape-casting technology, there's no extra beef and the integrity of every surface is essential to overall rocker arm strength. Grinding a groove to provide clearance (pen points)-then adding a stiffer spring-will lead to a fracture. A stock Chrysler rocker is shown for comparison on the left. Also note the size difference between the 0.900-inch Chrysler retainer and the 1.155-inch titanium replacement (right) that's required to match the up-sized spring diameter.