Stacking Compounds on a Factory 6.7L Power Stroke Bottom End
Our quest to push a bone-stock ’17 6.7L Power Stroke long-block beyond 800-rwhp kick-started a while back with the addition of 60-percent over injectors and a 10mm stroker CP4.2 from Exergy Performance. Now, we’re moving on to the air side of the equation. But instead of playing it safe by running a big single, we’re putting Ford’s “updated” connecting rods to the ultimate test by way of No Limit Fabrication’s compound turbo system. Chosen for its superb fit and finish, great drivability, and horsepower potential, No Limit’s kit combines a Precision atmosphere charger with a stock-location VGT. In our case, we opted for an 82mm Precision out front (over the kit’s standard 76mm Precision), and a Fleece Performance Engineering 63mm FMW Cheetah in the valley.
In preparation for the additional boost and the inevitable cylinder pressure that comes with it, we performed several peace-of-mind modifications, too. First, and because the 6.7L’s crank gear has been known to slip with big power in the mix, we pulled the front cover and welded the crank gear to the crankshaft. While we had access to it, the cam gear also received two welds. Then, in an effort to make sure the engine always sees adequate oil pressure at high load, H&S Motorsports’ billet oil pressure regulator was installed. Assured the crank and cam gears aren’t going anywhere, and that 60 to 80-psi of oil pressure will be on tap when it’s needed most, it’s time to see what the factory long-block is made of.
If the engine survives a trip to the dyno, we’ll have some horsepower numbers for you in Part 3. Stay tuned.
Flirting with Disaster
Since its inception, the 6.7L Power Stroke rods have been a weak link any time they’ve been pushed into 700-rwhp territory. Add big fuel and a compound turbo system that boasts a VGT in the valley and you’ll see the kind of cylinder pressure (i.e. low-end torque) that’s known to bend the factory units. While the rods in Job 2 ’17 model year and newer engines are believed by some to be stronger (they make use of a 1mm larger wrist pin), the verdict is still out as to how much power they can withstand. In short, we know we’re asking for trouble in putting this series together. Don’t try this at home unless you have plans to run a built engine eventually, or plan to detune things to a safer power level.
Fleece Performance Engineering
No Limit Fabrication
Precision Turbo & Engine