TRULINK SYSTEM | VIBRATION DAMPENER | INTERNAL BOOSTER | ENGINE OIL TREATMENT
TruLINK SYSTEM
Even before 1993, when the headline "New Low-Drag Valvetrain" graced the cover of Circle Track magazine, Alex Decuir had been diligently working on performance and durability in the internal combustion engine. Members of the Circle Track editorial staff attended an independent, day long, dyno test at Keith Black Racing Engines and published those results in their magazine. Everyone but the inventor was astonished. The baseline engine was a small-block Chevy 358CID that had had over 70 dyno passes and several races since it was built. It used stock cast heads, a two-barrel Holley carburetor, 11.0:1 compression ratio and 1.5-inch restrictor plate. The engine produced 366 horsepower at 6600 rpm and 352 lb-ft of torque at 4000 rpm. The Trulink system was installed (which only took a couple of hours) after baseline had been established. Jack Russell, an employee of KBRE, who was previously the chief engine builder for Morgan-McClure Racing, ran the test series on the system. No parts beyond the Trulink system were changed or altered. The carb jets, distributor advance, heads and camshaft were the same for final runs as far as the baseline. Even though the results were impressive, it was obvious to the editorial staff and Jack, that with some minor tuning, there would be much greater gains across the board. The test engine was a worst-case scenario, it being severely restricted.
The Trulink system is simplicity itself. The valves utilize a single valve spring with a seat pressure that's about 50% less than normal. A second valve spring is installed on the pushrod and is retained by a standard valve spring retainer resting in a groove on the pushrod. The spring seat is on an aluminum plate that attaches to the underside of the head in the lifter valley. As with a standard valve spring, shims are used to obtain the correct spring seat pressure. The seat pressure on the pushrod spring is very low, 22 to 25 pounds on the test engine. The rocker arm is a modified roller rocker. The pushrods are tubular and have a rod end securing the pushrod to the rocker arm. This allows the pushrod spring to help move the pushrod and rocker, and keep the lifter following the camshaft profile, especially on the downside of the lobe. THIS IS NOT A REV KIT. The Trulink system significantly reduces the possibility of valve float.
The key to the success of the Trulink system is reduced drag. The lower spring seat pressures allowed by the pushrod spring reduces drag throughout the valvetrain. This was most noticeable at the camshaft/lifter interface. It is here where most of the horsepower increase is found. It simply takes less horsepower to open and close the valves. What is less apparent with the lighter rate valve springs is an improved ability of the lifter to follow the camshaft lobe profile.
The cam profile and valve mechanism are more closely coupled because of the added pushrod spring and the rod end directly activating the rocker arm. This reduces valve float and allows more aggressive ramps and higher engine rpm. An additional side benefit is reduced component wear. Less drag translates into better wear characteristics. With all the dyno and race time on the engine, the valve springs have lost only 5% of their rate. This compares to a 15% loss in rate for the traditional setup after one race in the same engine. Timing chain stretch is reduced and cam, lifter, and rocker wear improved as well. Valve springs will last longer and valve and valve seat wear reductions mean fewer valve jobs.
The Decuir Trulink rocker arm system uses a pushrod that looks standard BUT is grooved for a valve spring retainer (arrow), just like a valve stem. Also note the aluminum plate bolted to the bottom of the head. This plate supports the base of the pushrod spring.