Muscle Mustangs & Fast Fords
Ford Modular Engines - Follow The Leader - Tech
Jesel Double Roller Cam Followers Add Horsepower And Control Valve Float In Modular Engines.
For many Ford enthusiasts, merely uttering the words modular engine conjures thoughts of complexity and uniqueness. The overhead camshaft design and different-looking cylinder heads have the die-hard pushrod-engine crowd confused. In addition, the valves open and close using a camshaft on top of each cylinder head-a far different way of doing things when compared to its in-block cam cousin, the pushrod engine.
Despite their uniqueness, modular motors are susceptible to the same shortcomings as its 302 and 351 brethren-friction in the valvetrain and a loss due to flexing of the components used to push the valves open. There's also a stabilization issue that can be improved upon with better-than-stock parts. Eliminating as much friction and flex as possible by adding stronger parts will yield more horsepower due to efficiency and valvetrain stability at increased rpm.
It's common practice to swap out the stamped rocker arms in 5.0-liter combinations and replace them with roller rocker arms. The positive power results have been proven time and time again in the pages of MM&FF. While those rocker arms are pretty much standard issue in the pushrod segment of the industry, they were rare in the modular world-until now.
Jesel Valvetrain recently introduced its double roller cam followers as a replacement for the OEM stamped-steel units. The cam followers are designed for use with hydraulic roller camshafts and solid roller cams, so long as Jesel's solid lash posts are also used. Cam followers are a self-described item and are the equivalent to rocker arms on pushrod engines. They connect the cam lobe to the tip of the valve.
A reduction in friction comes through the use of needle-bearing rollers on the valve tip and camshaft. The use of that type of roller prevents scrubbing and galling caused by intense spring pressure and high-rpm operation. The body of the cam followers is CNC-machined from aircraft alloy steel that's heat-treated for added strength. Features such as those are what make these components a must-have for any serious street/ strip modular engine. The drawback comes in the expense of such components (priced at $115 per follower), but the old adage holds true in that you get what you pay for. They're worth the expense.
High-end racing engines will benefit from converting to Jesel's solid lash posts and matching cam followers. Lash posts are the equivalent of lifters in a pushrod engine. Jesel builds its lash posts to be adjustable, using a variety of shims to get the proper valve lash. The tip is designed to stay engaged with the cam followers. Switching to the solid lash posts has the same added benefits as a solid roller lifter. They're able to use a more aggressive camshaft lobe and have a greater lift with severely increased rpm. It's common for race-oriented modular engines to see the high side of 9,000 rpm. We've even heard of a few racers checking out the 10,000- to 11,000-rpm zone. That amount of rpm certainly requires solid lash posts and sturdy cam followers to prevent valve float and possible valvetrain failure. Solid and hydraulic style cam followers are sold in Two-Valve and Four-Valve configurations, and Jesel is working on a design for Three-Valve engines.
We secured a supercharged Two-Valve combination as our test subject and baselined it on the chassis dyno at JPC Racing. Proprietor Justin Burcham had backed down the timing as a safety precaution for our barrage of dyno pulls. Everything we did was backed up within 1 percent-on both the baseline and subsequent testing. The '02 Mustang GT spun the dyno to an impressive 655 rwhp and 605 rwtq. This GT isn't considered ordinary due to the stout engine package under the carbon-fiber hood. A VT Racing-built Two-Valve modular engine has a fortified bottom end, ported Two-Valve heads, and custom VT Stage 3 camshafts. On top of the 302ci stroker engine is a Fox Lake P-51 intake manifold. Also, there is a ProCharger D1SC blower with larger blower tubes done in-house at JPC Racing. Backing the muscular modular is a T-56 six-speed transmission. Burcham has made 710 rwhp with higher timing, but he backed it down for the testing to the 655-rwhp baseline we achieved the morning of the install.
The Jesel cam followers went in easily, to say the least. In fact, it was one of our easiest install stories in recent memory. JPC has a tool from Ford that is required to swap out the cam followers. Other than that, we used the usual assortment of tools required to remove the valve covers. Installation took only a few hours, including us stopping JPC technician Adam Humm multiple times for photographic purposes.
The final results are interesting. We picked up 42 peak rear-wheel horsepower, a number that doesn't tell the whole story-more on that later. Burcham made three straight runs within a few horsepower of the new peak of 705 rwhp and torque sat at a lofty 633 lb-ft-some 33 lb-ft better than the baseline. Our gains were repeatable, showing the cam followers helped this engine tremendously.
As impressive as those gains are, we felt the story behind them was that this particular engine was suffering from valve float thanks to 20 psi of boost and 6,500-rpm dyno pulls (7,000 rpm on the racetrack). According to Scott Cushman of VT Racing Engines, this engine was built to make around 550 hp with about 14 psi of boost and 6,000-rpm shift points. The larger supercharger and increased rpm range are well out of the realm for the valvesprings and stock-cam followers.
We feel the test bullet had such impressive gains because the Jesel cam followers brought stability to the valvetrain. "The stock cam followers were most likely flexing badly under the load," Jesel's Bob McDonald says. The deflection most likely caused valve float. That's not to say the Jesel pieces won't pick up power in every engine; they will increase horsepower, and the gains-in our case-are on the high side. Some sources we spoke with have said they've generally seen 25- to 35-rwhp gains with the Jesel cam followers in similar combinations.
We performed another test, one on a naturally aspirated Two-Valve engine that's slated for use in NMRA Factory Stock. The stock short-block has ported stock heads, custom Rich Groh Racing camshafts, and runs mid-11s on drag radials with no power adder. This combo is mild when compared to most other naturally aspirated Two-Valve combinations, due to class restrictions. In this test, Burcham reported a 10hp gain, shooting up from 321 to 331.5 at the rear wheels. The torque curve also experienced similar increases throughout.
Pushrod or modular, reducing friction and adding rigidity to valvetrain components yields greater horsepower in mild and wild combinations.