Muscle Mustangs & Fast Fords
Ford Stock-Block Stroker Engine Swap Part 2
Dyno Testing Our Home-Built EFI 331 Stroker Is Only The First Stage For This Affordable Small-Block.
In the May '09 issue, we brought you Part 1 of our home-built stroker small-block Ford engine. Within the story, we detailed the brand new Fast As Cast Trick Flow cylinder heads we were using, along with the other Trick Flow components that adorned our Competition Products stock-block-based stroker motor. This month, we're finishing off the engine with some fuel and induction parts, and we're taking it to the engine dynamometer to flog it.
MM&FF has done its fair share of testing on both engine and chassis dynamometers, and for this build, we plan to do both to accurately determine the drivetrain loss after dropping the small-block in a Mustang coupe. The engine dyno results will also provide us with optimal information for choosing the correct torque converter for the car. Knowing the torque curve and the rpm range of the engine will help us dial in the converter choice for the best on-track performance.
To refresh your memory--or to introduce you to our mule--we recently screwed together a 331ci small-block stroker engine using a stock 5.0L block, as well as a forged rotating assembly from Competition Products. The components included in the kit allowed us to drop in a bored and stroked combination without the need for the block modifications that most stroker assemblies require. Topping off our seasoned short-block is a pair of Trick Flow Specialties new Fast As Cast 190cc aluminum cylinder heads, along with a Trick Flow R-Series intake manifold and a Trick Flow Stage II hydraulic roller camshaft.
Being that this engine will largely see duty at the track, we would have liked to have gone bigger on the cam, especially given the airflow potential of the Fast As Cast heads, but we were limited by the conventional valve reliefs in the pistons, which shorten up the ever-so-important piston-to-valve clearance. Down the road, we may swap out the pistons for a set of Trick Flow-specific pieces, but we'll have to look at our ultimate goal for the engine. If we go with a power adder, we may reach the limit of the stock block before we need to go with a more aggressive cam profile.
After completing the assembly of our stroker, there were a few items that we needed to finish the assembly and ready it for dyno testing. A call to Trick Flow Specialties netted us one of the company's TFX EFI fuel-rail kits, which includes billet-aluminum fuel rails, an adjustable fuel-pressure regulator, several AN aluminum fittings, as well as several lengths of braided stainless-steel fuel line. The kit (PN TFS-51580001) retails for $543.95 through Summit Racing Equipment.
To feed those heavy-duty fuel rails, we called up the fuel experts at Aeromotive and ordered one of the company's A1000 electric fuel pumps, along with a pair of inline fuel filters. The A1000 pump can flow 600 lb/hr of fuel and is rated for 1,300 normally aspirated horsepower, or 1,000 hp when used on a forced-induction combination. We plan to use the A1000 setup on future engine dyno tests at the Horsepower by Hedrick dynamometer facility.
Mark Hedrick, proprietor of Horsepower By Hedrick in Jacksonville, Florida, has been turning out high-performance racing engines for his word-of-mouth customer base for over 37 years. After turning a successful machining and engine-assembly side business into a full-time enterprise, Hedrick now caters to hardcore racers, boaters, and the occasional street-machine enthusiast. In addition to machining and assembly, Hedrick also offers dynamometer testing and tuning at his Jacksonville facility, and it's there that we set about testing our home-built small-block Ford engine.
Between the two testing methods, most MM&FF readers will no doubt be more familiar with the chassis dynamometer. These proliferate many high-performance shops across the country and beyond, and provide performance data and tuning information with relative ease and speed.
One of the great features of the chassis dyno is how easy it is to park a vehicle on it, strap it down, and get to testing. This takes all of about 15 minutes. The biggest problem with the chassis dyno is that it can't give you an accurate measurement of how the engine alone is performing, because the transmission, rear axle, and tires create friction and resistance that robs power and torque from the engine before it's converted by the dynamometer's computer program. There are percentage estimates that we use in the industry, but they are only estimates. As power increases, there will always be greater driveline friction, and thus, a greater percentage of loss. So, in short, there is no uniform percentage of loss. Nevertheless, we plan to do both types of testing with this engine.
In taking advantage of everything the engine dynamometer has to offer, one can extract horsepower and torque numbers, as well as exhaust gas temperatures, air and fuel consumption figures, water and oil flow, in and out water temperatures, and more. Plus, the engine dyno make it much easier to swap out major engine parts for testing, such as cams, heads, and headers.
The more high-strung your powerplant, the more you need an engine dyno to dial in the tuneup. Formula 1 teams even use engine dynos that can simulate the engine loads from a specific racetrack on a turn-by-turn or lap-by-lap basis. With this level of information, F1 teams can tailor engine specifications to each track, and also (attempt to) ensure reliability over a race season.
In this engine test, we're not going to such an extreme, but we wanted to break in the engine on the Horsepower by Hedrick dynamometer, and then tune it for optimal power and torque. We'll follow this test next month with more dyno testing on a different induction system, and finally the aforementioned chassis dyno test so we can determine the exact loss through the drivetrain.
As you are able to extract more data from an engine dyno, it is a bit more laborious when it comes to bolting the powerplant up to the dyno. We spent several hours sorting out throttle actuation, header clearance, and other assorted issues.
We intended to use a stock A9L Ford EEC-IV computer to run the EFI system, and so we could do that on the engine dyno, we ordered one of Ford Racing Performance Parts' new M-12071-A50 electronic fuel-injection harnesses. It's designed with the crate motor guy in mind, who wants to run the factory electronics in his hotrod but doesn't want to modify an old, crusty harness. It has provisions for an electric fan, tachometer lead, fuel pump power, air conditioning switch, and more. The harness comes with great instructions on how to get your engine up and running in no time flat, and if you have a Fox-body or SN-95 Mustang, it will easily replace your factory harness as most of the harness extensions are designed with those chassis in mind.
Tuning the EEC-IV box was handled by Tony Gonyon of HP Performance in Orange Park, Florida. Gonyon uses SCT software to write the program and burn it to one of SCT's computer chips. In addition to the tuning software, Gonyon also employs a SnEEC EEC-IV datalogger from Race Systems. It's a piece of hardware that is no longer produced, but it allows for optimal tuning of EEC-IV-controlled engines.
After entering the engine specifications into the dyno software, we cranked up the stroked small-block Ford and Mark Hedrick performed a break-in regiment, which loads and unloads the engine and alters the engine rpm. Having the dynamometer do this rather than having a human manually operate the dyno makes the process much more accurate and less tedious for the dyno operator. With the break-in complete, Hedrick made a few low-rpm, full-throttle pulls to creep up on the max rpm he had set at 5,500.
With the air/fuel ratio looking good, the oil temperature reading a steady 150 degrees, and the water temp at 140, our first 5,500-rpm pull netted 390.4 hp and 378.1 lb-ft of torque. This came with 29 degrees of total timing. For the next pull, we raised engine rpm to 6,000; peak power went to 398.3 and peak torque arrived at 378.3. Average power and torque was up thanks to a better air/fuel ratio. For the third pull, fuel was trimmed between 4,000 and 4,700 rpm, and ignition timing was increased to 31 degrees total. Peak power came in at 396.7 and the torque logged at a peak of 377.3 lb-ft.
We were thinking the tuneup was dialed in, so we made another pull to back the third run up. But this time at 5,600 rpm, power and torque dropped off by some 70 hp and 70 lb-ft! After a quick inspection, we tried again but the engine coughed at 3,800 rpm and we aborted the pull.
The first thing we checked was ignition timing, and we noticed it was moving around--it's not supposed to. After swapping out all of our electrical components for new ones, we still had the same misfire between 3,300 and 3,800 rpm. We then performed compression and lead down tests, which showed that the engine was healthy. It was late on Friday and we decided to call it a day.
The following Monday, we planned a carbureted induction setup to rule out a bad wiring harness, injector, or other EFI-related problem. Over the weekend, Hedrick also wondered if the cam was walking in the block, as it would explain the erratic ignition timing. As we pulled the engine down, we noticed that the camshaft was indeed moving nearly a quarter inch in the block. This will affect how the distributor gear and the cam gear mesh, which can alter the timing and cause a misfire.
While we don't recall any issues with the cam gear during installation, it was evident that there was no endplay on the cam and gear, and this tight fit caused the cam bolt to back out, which allowed the camshaft to slide back and forth in the block. Hedrick determined that the brass bushing behind the cam gear wasn't sitting on the gear correctly, so he took it and the cam retaining plate to his machine shop and milled them down until the bushing was flat and the combination offered 0.005-inch endplay. He then degreed the cam (you'll see that in an upcoming tech article), and HP Performance's Jason Combs and Jimmy Hartley reassembled the engine--this time with a carburetor.
We're going to throw the EFI setup back on the engine, but since we had the time, we opted to test both so we could compare the two setups. The carburetor is a Holley 650-cfm four-barrel with vacuum secondaries, and the intake manifold is a Professional Products Typhoon dual-plane, air-gap-style intake. We don't know if it's optimum, but it was sitting around so we went for it.
We'd like to thank Mark Hedrick and Jimmy Hartley, along with Tony Gonyon and Jason Combs, who went above and beyond to get our stroker small-block running tip top and make this test happen. There are always risks when assembling your own engine at home. That's why there are professionals like Horsepower By Hedrick, who offer professional machining and assembly services. If you're not up to the task, they are, and they build their reputation on the fact that they do it right the first time.
In any case, check out the next installment of our stock-block stroke swap to see how the carburetor fared against the EFI setup.