Steve Turner
Former Editor, 5.0 Mustang & Super Fords
December 1, 2000
Photos By: Mike Johnson

Step By Step

View Photo Gallery
138_90z 1996_ford_mustang Engine_view
Here is Doug’s engine inside the legendary Young’s Performance dyno cell, which is in the shop just outside Wayne Young’s house. The 9.2-inch block weighs in with 375 ci thanks to a Scat crank, GRP rods, and JE pistons. All told, the engine rumbles with blower-friendly 8.5 to 8.7:1 compression. Once Wayne finished tweaking the Speed-Pro fuel injection, this engine cranked out 1,585.8 hp and 1,010.8 lb-ft of torque (see On the Dyno sidebar).
138_92z 1996_ford_mustang Engine_view
Here’s the blown 375 Windsor back in Doug’s ’96 GT chassis. The sheetmetal box hanging on the front of the car is Doug’s air-to-water intercooler, which chills the engine’s inlet temps around 100-110 degrees. Doug says even though he has to refill the intercooler between rounds, the blower combination still requires less maintenance. They do have to run the valves every round, however, because he is spinning the relatively small motor to nearly 9,000 rpm, where the nitrous combo was only into the high 7,000s.
These days it takes more than one person to put together a successful Pro 5.0 effort. Here Doug Mangrum (left) chats with his cylinder head and intake porter, Tom Cox (middle), and his fuel-injection tuner Wayne Young, (right). Wayne likes cylinder heads to flow a lot before he straps on a supercharger. Tom reworked Doug’s early Yates casting so they flow 400 cfm on the intake and 300 cfm on the exhaust.
138_01z 1996_ford_mustang Scoop
Doug thought the supercharger was starving for air at the top of the track because of the vacuum created under the engine at speed. As such, he enlisted Mike Duffy at Mike Duffy Race Cars, who also built the car, to fashion a box behind the blower and a mailbox-sized scoop to ram air into the back of the blower.
138_02z 1996_ford_mustang Engine_view
They were rewarded with nearly 2 more pounds of boost at the top of the track. So, you can expect to see a bunch of funky-looking scoops on the other Pro 5.0 cars.
138_03z 1996_ford_mustang Left_front_view

Like it or not, the times are changing in Pro 5.0. Nitrous has been a part of the quickest 5.0 Mustangs in the land since the early days. Stormin' Norman ran the first 10-second e.t.'s with nitrous. Even in recent history, Doug Mangrum was the first to run 7s in his venerable '92 GT in 1998. During the first wave of the evolution--the move to 25.1C chassis certified for runs quicker than 7.50 seconds at more than 170mph--Doug brought his trusty carburetor/nitrous combination with him.

It looked as though nitrous was going to be there for Doug's next Pro 5.0 milestone. But something happened. Where Doug's carb/nitrous motor had once been a consistent, low-maintenance performer, he suddenly had a trail of burnt pistons behind him. "Somehow we lost our combination, our edge," Doug says. "At times we'd have it and at times it would change. We just really couldn't grasp it. We just kept changing part after part and spending the money and burning up pistons in the process. After about four or five sets of pistons, I started thinking, Is there a better way?"

It was a tough choice for Doug. He had long been loyal to his nitrous sponsor, but after consulting his friends and going with his gut instinct, he decided a supercharger might just be the way to go. Inspired by the impressive performances of Joel Greathouse's Super Street ride, Doug decided a ProCharger and a Wayne Young Speed-Pro tune-up just might be the way to go. At the Bradenton Fun Ford Weekend, Doug had toasted another set of pistons, so he sought out Wayne.

According to Doug, Wayne said, "Hey, if you decide to make a change, I think we can make some good horsepower. The way Joel is running, that speaks for itself. I'd love to work with you on it, and we'll give you a quote."

After further consideration, Doug worked out a price with Wayne for the setup and tuning, and Ken Jones at Accessible Technologies for the big ProCharger. Doug had to sell some things and borrow a bit of money from the family to put together the cash for the fuel-injection conversion, but he managed. Typically this conversion costs $15,000, but that includes the fuel system, Speed-Pro system, supercharger, brackets, belts, and everything else needed to get the new combo running. With the money in hand, Doug simply had to convert his existing engine setup to Wayne's blower specs.

Wayne is nonchalant about the whole conversion process, making it sound about as easy as making scrambled eggs for breakfast. "I convert their intake over to fuel injection," he says in his slow-paced Southern drawl. "I tell them to give me a long-block with a certain compression ratio and heads that flow as much as they can. I build brackets and motor plates. I mount everything, put it up on the dyno, build a fuel map, give it back to them, and tell them to put it in the car."

There's a bit more to it than that, however. Doug got together with JE pistons to help him decide on the proper crank stroke and pistons to work with his existing GRP rods. While Keith Craft assembled the revised short-block, his other longtime sponsor, Tom Cox at Tom Cox Cylinder Heads, enlarged the plenum area of his cast intake manifold and squeezed even more airflow from his early Yates cylinder heads. A new blower-grind cam from Cam Motion makes the whole assembly work with the blower.

"Wayne did all his stuff with the bracketry and his magic with the tuning," Doug says. "He was able to extract 1,585 hp out of it."

Doug's old engine combo made 800 naturally aspirated horsepower on the dyno, so it would obviously take a lot of nitrous to get it in the neighborhood of the blower motor. More power is good, of course, but the new blower/fuel-injection combo is "another can of worms" for Doug. So far, they just haven't been able to apply the power they have to the track.

"I think it's a good combination to work with," Doug says. "It's gonna make good power, and we're not quite using to the power we have. Once we get there, I think ProCharger can come back to the board and help us out a little more. As it stands, no one has really optimized their combinations."

So for all the hubbub over the turbo-charged five-speed Pro 5.0s, we've yet to see the full fury of a centrifugally supercharged/five-speed Pro 5.0. Of course, Doug is hoping he can be the one to do so. At the National Mustang Racers Association's Gateway tilt outside St. Louis, Missouri, Doug managed to run a 7.655 at 183.67 in sticky heat. This was achieved with his clutch adjusted to the limits for as soft a hit as was possible.

Doug is determined to find a better way with the clutch too. He will be switching to a new clutch setup in hopes of getting deeper into the 7s, so hold on to your Liberty gear knobs. Doug's gunning for a new milestone. He wants to trade those 7.70 nitrous passes for some 7.50-7.40 blower passes. That should be some swap.

Horse Sense:
The massive ProCharger D3M supercharger on Doug's car features a 12-inch housing with a 4.7-inch inlet, a 7-inch impeller, and a 3.59-inch outlet. It supports a maximum impeller speed of 56,000 rpm, a maximum airflow rate of 2,900 cfm, and a maximum horsepower output of 1,650. Depending on the engine it's bolted to, the D3M can generate up to 36 pounds of boost.