I have a passion for big-inch motors, and this has led me to ignore Ford's 4.6 Mod motor and its potential. What a mistake, and one we're about to rectify. The reality is that Ford's modular engine, especially the 4.6, is a cheap buy on the used market, and has way more potential than the modest displacement might suggest. But as Andy Wood of Cross Roads Performance (Gastonia, North Carolina) will demonstrate here, the lack of inches is not the big handicap you might think-as long as all mods are done right. In small, low-budget steps, we're going to show you what can be done for the mod motor.
The original plan was to install a low-mileage 4.6 from a bent '97 Mustang into an inexpensive '89 Fox-body rolling chassis. Mod motors have become popular for this and other transplants but wouldn't you know, running across an immaculate '96 Mustang with a large hole in the pan changed all that. So that good stock '97 motor went right into the '96, and that's where our investigation into mod motor speed starts. We started with proven mods demonstrated to work on many previous occasions. To understand how things progressed with the dyno numbers and drag testing, we'll discuss that here so you can see how we arrived at the final results.
The first move was to take the '96 over to Aaron Lail's Tru Dyno Sports (Hickory, North Carolina) where they dyno'd it on his Mustang chassis dyno. Everything was set to factory spec to establish a baseline rear-wheel power and torque curve. This proved to be 182 hp at the wheels. At Shadyside Dragway-our local eighth-mile track-the stock '97 stopped the clocks at 9.72/74.50 mph, which unofficially computes to a 15.97 at 84.71 mph for the quarter-mile.
Gears And Tires
This thing couldn't break the tires loose to save its life, and a lackluster 60-foot time prompted a rear-end change from the stock 2.73 ratio, to a 4.10 ratio. The green gear set with its lower ratio cost a little in the way of horsepower, but the rear-wheel torque in First gear was up by 33 percent, so the launch would be much better. After collecting a set of M&H slicks, we went back to the track and tested, with the eighth-mile result of 9.56/76.21.
Late-model Mustangs look great,...
Late-model Mustangs look great, but compared to traditional muscle cars or their GM competition, they just aren't that fast. This '96 GT test mule looked really sharp with its replacement '97 engine installed, it just wasn't fast.
Cams And Exhaust
The next mods are being thrown in because the parts are readily available on the used market, and often at bargain prices. They don't produce earth-shattering results, but assuming a typical used price, they do represent a cost-effective move.
The parts we're talking about are a set of factory "performance improved" (PI) cams from a stock '99-04 Mustang, some Ford Racing shorty headers, and a MAC off-road H-pipe and mufflers. These mods turned 198 hp on the chassis dyno, for an increase of 19 hp over baseline.
Back at Shadyside, we found that the M&H slicks effortlessly planted the extra power, and our Mustang reeled off some consistent runs with the average at 9.17/78.10. This approximates a 14.98 e.t. for the quarter, so we have passed a significant milestone already.
Hot Cams And Compromises
Here we come to the first "speed secret" known by Mod motor specialists like Andy Wood. From many hours spent on the chassis dyno, Andy reports that a typical 4.6 engine produces the best results when the cam lobe centerline angle is at 108-109. But most cams sold are on a 113-114 LCA. Why? The problem is that the stock pistons have no valve pockets, so giving the engine what it actually wants on a cam of a little more than 225 degrees at 0.050 tappet lift is going to put valves and pistons in the same place at the same time.