400 HP 4.6L Three Valve Stroker Build
Three-Valve’s Full - The making of L&R’s big-steam stroker for pre-Coyote S197s
The '11-present 5.0L Coyote engine now basks in the performance limelight; deservedly so, because it truly is a wonderful, world-class piece. However, Coyote's immediate Mustang predecessor—the Three-Valve 4.6L that is found between the fenders of tens of thousands of S197 GTs through 2010—is far and away the best of the single-cam 4.6L modulars.
Missing only the manly grunt of displacement to make it truly muscular, the Three-Valve was recognized as one of Ward's 10 Best Engines annually from 2005 through 2008, yet today can be found with or without the surrounding Mustang for surprisingly little money on the used market. For those seeking a modern yet affordable GT, these '05-'10 S197s can now be tremendous bargains. Add a touch of stroke along with a few carefully chosen breathing mods, and you've got the recipe for a bulletproof, street-friendly, 400-plus naturally aspirated horsepower without gutting the bank.
To put this theory to the test, we recently picked up a used S197 Three-Valve long-block for the paltry sum of $500 and sent it to L&R Engine in Santa Fe Springs, California, for freshening and muscle-building. We're completely manning up its bottom end with Lunati's forged-steel, 3.750-inch stroker crank; Scat forged H-beam rods; and Probe flat-top, 10.2:1, forged pistons.
Up top, the stock Three-Valve heads were treated to a little of L&R's careful bowl work, then re-valved and fitted with an aggressive yet streetable set of Lunati Voodoo hydraulic roller cams that are just a notch or two more gnarly than Ford Racing Performance Parts' Hot Rod bumpsticks.
Speaking of FRPP, we're harnessing its tall, black composite manifold for induction duty. And that's about as far as we'll go this time around, because, well, we're still looking for a suitable S197 GT to receive this bumped-up bullet (and many thanks to our friends at Brenspeed Texas for helping us with this effort).
So, as the calibrator might say to the PCM, stay tuned.
3. At left is out three-valve's old factory cast crank, with it's 3.543-inch (90mm) stroke. Plenty strong for near stock power levels, it pales in comparison to Lunati's signature series forged 4340 steel replacement on the right, which the company says has proven to withstand applications over 1.500 horsepower.
4. With a torque-benefitting stroke of 3.750 inches (also available in 3.800), the Lunati crank’s main journals are gun-drilled; its 2.000-inch rod journals are lightened and micropolished (stock Modular rod journals measure 2.086 inches).
5. Any engine build is only as good as its fasteners, and L&R seemingly threw just about the whole ARP catalog at our Three-Valve project. It’s interesting how this one company has come to utterly dominate the engine assembly fastener market.
7. Natural aspiration is our plan for this project, so Probe Sportsman Race Series (SRS) flat-top forged pistons were spec’d for our engine’s 0.020-inch over-bore. The slugs have a compression height of 1.048 inches, use a standard 1.5/1.5/3.0mm ring package, and are designed for modular use with 6.000-inch rods for 3.750-inch-stroke applications.
8. One of our Scat forged 4340 H-beam rods is shown in comparison to a stock Three-Valve example. Nothing custom here, just simple rods with 2.000-inch big ends and 6.000-inch length. The fasteners are 12-point ARP cap screws.
10. Derek gets assembly underway by locking down the Lunati stroker crank. Primary fasteners are ARP’s 190,000-psi main studs (PN 156-5901), though each 4.6L Three-Valve main cap has an additional quartet of fasteners.
13. The piston/rod combos are then slid in down through the bores and torqued to specs. This shot also shows the Three-Valve’s main-cap cross bolting. With beefy caps each secured by a half-dozen fasteners, this is a solid bottom end structure.
16. L&R performed its Stage 2 bowl porting on our castings, cut in a three-angle valve job, and fitted a new set of SI valves. At 35 mm (intake) and 38.5 mm (exhaust), these are 1mm larger than their factory counterparts. The SI valves are crafted of EV8 stainless, with hard chrome stems and stellite tips.
18. We’re using a set of Lunati’s Voodoo hydraulic roller cams (PN 21270716). With 112-degree lobe separation, gross lift of 0.500/0.508, and 233/241 duration at 0.050, these are what Lunati describes as “awesome street cams with rough idle,” even though our stroker’s roughly 20 extra cubic inches of displacement will have something of a calming effect on these bumpsticks.
19. Those cam phasers are necessary because the 4.6L Three-Valve was the first to employ variable cam timing (VCT) to benefit power and efficiency. A solenoid, under electronic command of the PCM, sits at the forward end of each head and slightly retards or advances its cam as commanded by varying engine oil pressure within the cam phasers (which are not installed in this shot).
21. For now, we’re finishing by bolting on Ford Racing’s Three-Valve-specific composite intake manifold (PN M-9424-46Three-Valve). This piece was engineered to team with FRPP’s Hot Rod cams, so we think it should work well with our slightly more aggressive Lunati bumpsticks. Stay tuned to find out.