Quote:
ORIGINAL: klfutrelle
I thought your guys were talking about stroking out the 4.6.
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Here you go for stroking out your 4.6,
Engine Masters (Summer 2005 – Volume 8, No. 2)
Undercover Work (4.6L Street Stroker) Pg. 26-30
By Richard Holdener
I’m a firm believer in the notion that form follows function. I’d much rather have a car that goes 200 mph than one that looks the part but never sees the light of day. Taking that scenario one step further is the sleeper concept. What looks to the entire world like a stock machine is actually something decidedly more wicked. Using the mild mannered exterior to lure in unsuspecting victims, the sleeper relies on a healthy dose of hidden horsepower to finish them off. In the automotive world, sleepers come in many shapes and sizes, but the concept is still the same. Build a motor with heaping helpings of extra horsepower and do your very best to package it in a plain brown wrapper. In this case, the plain browm wrapper equates to stock external components visible with a cursory inspection. These components include the factory block, heads and intake manifold. The idea is to camouflage your efforts by making the engine bay appear as stock as possible. In the case of this stroked 4.6L modular motor that meant having an engine bay full of nothing more than your average 2V 4.6L GT motor. No one even looks twice at a 4.6L 2-valve Mustang, especially a stock motor without so much as a blower, turbo or nitrous.
What they don’t realize is this modified 5.0L stroker can run every bit as hard as a blown 4.6L, but manages to do so without resorting to pressurized power or even compressed liquid assistance. While blowers, turbo and nitrous all have the ability to greatly enhance the power output, this build up was designed to illustrate what can be accomplished sans power adders. When you go looking to increase the power output of your modular motor, think cubic inches. Unfortunately for modern Blue-Oval enthusiasts, the basic architecture (actually bore spacing) of Ford’s modular motor limits the available bore size. It is possible to resleeve the blocks, but you’ll never see the 4.125-inch or even 4.00-inch bores run on the earlier Windsor motors. With limited bore spacing; additional cubic inches must be obtained through increased stroke length. You can opt to install a larger 5.4L block, but the taller deck height creates hood clearance issues, not to mention the additional weight of the larger motor. Besides, the 5.4L option would not be in keeping with our sleeper approach. What does work is increasing the stock 3.54-inch stroke length to 3.75 inches. When combined with a 0.020-inch overbore, the result is an increase in displacement from 281 cubic inches (4.6L) to 300 cubic inches (5.0L).
Thanks to Coast High Performance (CHP), installing the longer 3.75-inch stroker crank into the 4.6L block isn’t any more difficult than picking up the phone and providing a credit card number. CHP offers 5.0L (and 5.1L with the maximum allowable bore size of 0.070-inch over) stroker kits complete with the 3.75-inch stroker crank, forged connecting rods and forged aluminum pistons. The combination will drop right into your professionally macined 4.6L block (iron or aluminum) or the kit can be ordered as a dedicated short-block. The mod motors kits are available in a variety of different compession ratios, but we chose a set of flattop pistons with valve reliefs to provide sufficient pistion-to-valve clearance for the rather large cams we planned to install. The flattop pistons combined with the additional stroke produce a static compression ratio of 11.25:1. Though a tad on the high side for street use with 87 octane, the motor was run successfully with 91-octane premium unleaded pump gas. The 5.0L stroker short-block was finished off with a stock oil pump, pan and pick up.
With the short-block taken care of, we turned our attention to the airflow portion of te equation. All those additional cubic inches were going to be worthless (or at least less sufficient) without a decent set of cylinder heads. In this case, the lack of aftermarket cylinder heads was actually a blessing in disguise, as utilization of the stock heads continued our stealth approach. Knowing that the flow rate offered by the stock heads was by no means sufficent for our stroker, we shipped off the factory 2001 PI aluminum cylinder heads to Total Engine Airflow. The heads were given TEA’s Stage 3 treatment, which included full CNC porting of the intake and exhaust ports, new Hi-Chrome valve seats (plus bowl blending) and even combustion chamber polishing to minimize the threat of detonation. The chamber was further worked to unshroud the oversized 47.7mm Manley intake valves and 36.8mm stainless steel exhaust valves. The ported heads were finished off by mod-motor maniac John Mihovitz, who performed the necessary vacuum test and valve job to ensure perfect sealing. Given the dissimilar valve lengths, it was necessary to install a 0.063-inch shim under each intake valve lash adjuster. The shims ensured adequate preload on the hydraulic lash adjuster.
The CNC-ported PI heads were topped off with a set of Xtreme Energy cams from the COMP Cams catalog. Given the displacement and compression of this 5.0L stroker and the fact that our newly ported heads flowed so much better than stock (the intake flow increased to 235 cfm at 0.550-inch lift), we selected a set of appropriate cam profiles. The XE278AH cams offered 0.550-inch lift (both intake and exhaust), and 242/246 duration (at 0.550-inch), and a 113-degree lobe separation angle. We knew that the 0.550-inch lift would take full advantage of the new airflow offered by the CNC-ported heads and that the duration figures would allow the motor to continue to make power right to 6000 rpm and possibly beyond. Finishing off the 5.0L stroker was a stock composite PI intake manifold. We found that the stock throttle body and inlet elbow were quite restrictive on this stroker motor (to the tune of 17 hp), so we opted to install a 75mm AccuFab throttle body and matching inlet elbow. While we would like to run the stock components to retain oursleeper status the reality is that throttle bodies are one of the first upgrades performed to 2V modular motors, so we felt that our stroker motor would just look like a stock 4.6L trying to be fast.
The 5.0L was assembled and run on Westech’s Superflow 901 engine dyno. As luck would have it, I recently ran a bone stock 4.6L PI motor (circa 1999) on the very same dyno under the very same conditions. The stock 4.6L (supplied by Sean Hyland) produced 287 hp at 4900 rpm and 332 lb-ft of torque at 3900 rpm. Equipped with the same F.A.S.T. engine management system, same 36-pound injectors, and same 1 5/8-inch stainless steel Kooks headers, the modified 5.0L street stroker thumped out an impressive 434 hp and 430 lb-ft of torque. True to form, the stroker motor exceeded 400 lb-ft from 3900 rpm to 5600 rpm, making for one heck of a torque curve. The motor ran best with an air/fuel ratio of 13.0:1 and with 26 degrees of total timing, though we tried other timing curves. Compared to the stock 4.6L (which looked identical on the dyno), the 5.0L stroker produced as much as 173 more horsepower and over 150 lb-ft of additional torque. Those are the kind of numbers you usually associate with a blower, turbo or even a heftydose of nitrous. The best thing about this stroker combination is that it maker blower power all the while looking like your run-of-the-mill 4.6L mod motor. I guess our work here is done.
Sources:
AccuFab
COMP Cams
Fuel, Air, Spark, Technology (F.A.S.T.)
Kooks Custom Headers
Total Engine Airflow
Coast High Performance
I give credit for this research to MuddyWoman on FordF150.net.
I was going to do it to my 99 F150 4.6, but them me being the good older brother making
RE: 5.4 = not enough credit
