Muscle Mustangs & Fast Fords
Installing A 331-Stroker Kit In A Small-Block - Stock-Block Stroke Swap Part 4
From The Engine Dyno To The Chassis Dyno, Our 331ci Small-Block Ford Is Put To The Test.
Over the past several months, we've been assembling and dyno testing a small-block 331ci engine. This month we conclude the buildup by installing the engine in the car and turning the chassis dyno rollers to see just what the powertrain loss is after backing it up with a C4 automatic transmission.
The engine in question began as a stock late-model 5.0L block, which subsequently had its cylinder bores enlarged 0.030-inch oversized. We then sourced the 331-cid rotating assembly from Competition Products. The assembly consists of a cast-steel crankshaft, Scat forged I-beam connecting rods, and forged-aluminum SRP pistons, and it comes with bearings and piston rings.
We chose the 331-stroker kit for the better rod ratio, and as we found out during installation, it didn't require any modifications to the block to clear the rod ends. Competition Products also provided a 157-tooth, small bolt circle, SFI-approved flexplate to connect the engine to the transmission; a Professional Products 28-ounce harmonic balancer; and a Melling standard-volume oil pump.
Knowing that the stroker small-block was going to move much more air than the stock 302, we called Trick Flow Specialties about an induction setup. To keep the fuel-injection (the engine is going in a late-model Fox coupe Mustang), Trick Flow provided us with its brand new "Fast As Cast" 190cc cylinder heads, which are a lower cost, cast version of the company's CNC-ported Twisted Wedge cylinder head. Trick Flow also supplied its Stage 2 hydraulic roller camshaft and a Trick Flow R intake manifold. We also sourced the needed pushrods, 1.6:1 roller rocker arms, timing chain, valve covers, gaskets, and TFX EFI billet fuel-rail kit from Trick Flow.
We buttoned up the bottom of the engine with a 7-quart oil pan from Milodon; the top of the engine was fitted with a BBK Power-Plus 70mm throttle body and EGR spacer from Brothers Performance Warehouse. We had a set of Ford Racing 30-lb/hr fuel injectors handy and used those in conjunction with a C&L mass air meter that we also had.
Summit Racing Equipment played an integral role in this buildup as well, supplying everything from ARP head bolts to gaskets to throttle cables. We often found ourselves in need of this or that, and Summit Racing had what we needed every time. And they got it to us usually the next day, thanks to the company's close Georgia location.
Hurricane Performance's Jason Combs assembled the engine, and we put it to the test on Horsepower By Hedrick's engine dyno. Once bolted to the Superflow dynamometer, Mark Hedrick proceeded with a programmed break-in routine, which seats the piston rings to the cylinder walls and ensures everything has been well lubricated. To get the fuel-injected engine to run on the dyno, we contacted Ford Racing Performance Parts and ordered a standalone EFI harness designed for 5.0L/5.8L engines. The harness just needed an A9L EEC-IV ECM, a 12-volt power source, and a ground to get the engine up and running. To make sure we maxed out the performance of the engine, we relied on Tony Gonyon of TunersInc to handle the necessary chip burning and datalogging.
On the dyno, the EFI combination produced a stout 396.7 hp at 5,800 rpm and 377.3 lb-ft of torque at 5,200 rpm. Readers who have followed this build may recall that we encountered a misfire after several pulls. After performing multiple checks and inspections, we opted to run the setup with a carburetor to see if it was a mechanical or electrical issue. The carbureted combination ran clean and posted 401.2 at 6,100 rpm, and peak torque checked in with 391.1 lb-ft at 4,700 rpm.