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.
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.