Muscle Mustangs & Fast Fords
Ford Stock-Block Stroker Engine Swap Part 1
We Build A 331CI Small-Block Ford, And You Can Do It, Too.
Dig in and prepare to get your hands dirty. It's time to add some cubic inches to your 5.0L Mustang, and it just might be easier than you think. With the average EFI 5.0L Mustang now some 20 years old, it's going to be time for a rebuild. For a few bucks more, you can add more cubes, more horsepower, and more torque.
A few issues back, we brought you a budget rebuild story called the "Recession Special." Adding new crank and rod bearings, along with new piston rings can freshen a tired 5.0L and give you a few more years of life from the tough-as-nails small-block Ford. This month, we're here to show you that you can employ those same techniques from the budget build and add a stroker rotating assembly at the same time.
We started with a seasoned 5.0L stock block and dropped it off at H&M Parts Warehouse in Jacksonville, Florida, where the crew bored the cylinders 0.030-inch over, performed a finish hone, and installed new cam bearings, freeze plugs, and oil-galley plugs--not bad for just a little over 200 bucks. Most stroker assemblies utilize custom pistons that move the wristpin higher in the piston to allow for the longer connecting rod, and since they're already making a new piston to allow for more cubic inches, it just makes sense to maximize the piston to do the same. That being the case, the pistons are made for a 4.030-inch bore size. We also had the machine shop hot-tank the block before they gave it back to us.
For our rotating assembly, we turned to Competition Products of Oshkosh, Wisconsin. Since 1970, the company has supplied engine builders and enthusiasts alike with great deals on everything from engine parts to oil. If it's under the hood or beneath the chassis, chances are Competition Products has something to replace it or make it better. After placing our order, we had the rotating assembly sitting at our doorstep in just three days. It might be quicker if you live closer, as it ships the same day the order is placed.
The engine will be shoehorned between the fenders of a Fox-body coupe Mustang, so we opted for the 331ci stroker rotating assembly as opposed to the 347ci option. It's a light car, and we'd rather forfeit the extra torque of the 347 for the better rod ratio the 331 offers. There's only $10 difference between the two kits. The basis of the 331ci combo is a cast steel crankshaft with a 3.250-inch stroke on the rod journals. Said journals swing 5.4-inch Scat I-beam connecting rods that have been fitted with ARP fasteners. Finally, an octet of SRP forged flat-top aluminum pistons will fill the cylinders and get the crank and rods moving.
Competition Products also includes HRC plasma moly file-fit piston rings and balanced the entire rotating assembly for us. The company also provided us with a Professional Products harmonic balancer for the stroker's 28-ounce imbalance, as well as an SFI flexplate to match our Mustang's C4 automatic transmission.
Topping off our stroked and poked short-block is a set of Trick Flow Specialties all-new Fast as Cast 190cc Twisted Wedge cylinder heads. TFS heads have always been relatively affordable, and in this day of CNC this and that, the company opted to give its consumers a CNC-sized port in a cast head for a cast price. Going off of its popular CNC-ported 185cc runner Twisted Wedge head, TFS used the port designs to produce a 190cc intake runner and 66cc exhaust runners. These 190cc runner heads retail for $1449.95, compared to the CNC-ported 185cc castings that sell for $1799.95.
"Our competitors have everyone believing that you need a CNC head to make power," says Trick Flow tech Greg Changet. "Some people will want a CNC head no matter what you tell them, but with the Fast as Cast head, you get the big runner without the big price." And you get the flow numbers, too. We'd like to see what a quick cleanup job could do with these heads, and we may get to that in a future article.
Rounding out the induction side of the 331 is TFS' 5.0L R manifold, a BBK 75mm throttle body, and a TFS Trackmax Stage 2 camshaft to move the air in and out. Best of all is that you can order all of the parts from just two places, and with the same-day shipping from Competition Products and Summit Racing Equipment, you can have the combination built and shoehorned into your street machine in no time at all.
This month, we're bringing you the buildup of the engine; then we'll follow up with an engine dyno test, a chassis dyno test, and conclude with a quarter-mile drag test. You'll get to see what the parasitic loss is from crank to wheel horsepower, as well as how this stock-block stroke swap performs in a Fox-body Mustang at the track.
Cylinder-Head Flow Numbers
Tested on a 4.030-inch bore. Flowed at 28 inches on a Superflow SF-600Lift