Ad Radar
Car Craft
Click here to find out more!

Make 503HP With A $350 Junkyard 302

How to Add 80 HP with a Simple Cam Swap

By , Photography by

Some ideas never go out of style. It's a classic Car Craft move we've pulled off many times. Yank a motor out of the junkyard, clean it up, add a camshaft, intake, and a carburetor and see how much power we can squeeze out of it. This time around, we chose a shining example of this junkyard art form. Car Craft family member Tim Moore was cruising the 'yard awhile back and located a '00 Ford Explorer with an EFI 5.0L engine. The SUV indicated barely 120,000 on the clock, and after yanking the valve covers to judge the engine's condition, he instantly made the decision to do the boneyard version of a smash-and-grab. Within a few hours of his discovery, the engine was sitting in the back of his truck on its way to a new home.

Beyond the engine's amazingly good appearance, Moore had a couple of good reasons for choosing this engine. The '00 Ford Explorers and Mercury Moutaineers were factory equipped with one of Ford's better 5.0L motors. These engines came with the GT40P head, which even with its small valves, offers really good performance. The engine was only rated at 215 hp but at least had 9.0:1 compression. These cast piston short-blocks are not quite as good as the forged piston 5.0L that came in Fox-body Mustangs, but the GT40P heads flow much better than earlier 5.0L heads. In addition, the cam timing was designed for torque, with duration somewhere around 190 degrees at 0.050 with roughly 0.450-inch lift.

We also discovered some issues with the GT40P heads that required changes, so we added valves from Manley that eliminated the exhaust-valve rotators and allowed us to set the proper valvespring installed height. The heads also required some machine work, including screw-in studs, guideplates, and widening the spring pockets for bigger valvesprings. We took the heads to Mike Slover of Slover's Porting Service in Sun Valley, California, to do this work, plus some basic pocket-porting to improve flow—especially on the exhaust side. We didn't increase the valve size, although we did have to add Manley valves to get the proper spring-installed height. We will go into more detail on the head mods in a later story in Junkyard Builder, so watch for it.

While the heads were off getting a massage, we turned our attention to the cam timing. The question was whether we wanted a torquey small-block or a more cammed-up rpm engine to boost peak horsepower. We decided to test both ideas, so we ordered two roller cams from Lunati: a shorter-duration cam that would deliver decent idle vacuum and maybe make around 320–335 hp, and a longer-duration version that might push the horsepower up to perhaps 350 hp. It turned out we were conservative on both counts.

As a final goal, we decided to bolt on a simple nitrous system and see if we could push this little small-block Ford to make some real power. There are caveats to this plan, however. We've seen what happens from previous Ford experience when power levels above 500 hp tend to either pop head gaskets or saw blocks in half. We decided on a Powerstar kit from Nitrous Supply, owned by our good friend, Mike Thermos, who was one of the original nitrous kit suppliers back in the early '80s. The kit offers adjustable power from 50–250 hp with a simple jet change.

Small-block Fords and Mopars only use four head bolts per cylinder, so retaining proper head-gasket seal—especially with nitrous—is a point that demands attention, so we ordered a set of Fel-Pro MLS head gaskets rather than a standard, composition gasket. The multiple-layer steel construction allows the gasket to conform to movement between the cylinder head and block while maintaining a good seal. They are more expensive than standard head gaskets, but they also do the job and are worth the additional money. For additional insurance, we also added a set of ARP head studs, which are stronger and offer better thread overlap than factory bolts, which helps prevent pulling threads out of a used block.

Finally, we exchanged the Explorer's EFI manifold (which is a pretty good manifold in its own right) for an Edelbrock Performer RPM Air Gap intake and a Holley 750-cfm HP style carburetor. We also added a veteran Ford magnetic pickup distributor and used it to drive an MSD ignition system. With the engine reassembled, we boxed up our second camshaft and headed for Westech's dyno.

We pulled this hydraulic roller-cammed 5.0L out of a junkyard '96 Ford Explorer, updated the heads, added a carburetor, headers, and a couple roller cams and made as much as 375 hp.

This is the motor with the GT40P head removed. The engine was in extremely good condition considering its mileage—the factory crosshatch was still evident on the cylinder walls. This can be partly attributed to Ford's hard iron block, but more importantly, EFI fuel control and superior lubricants, which help reduce wear.

One thing we didn't change on the engine was the original Explorer's uniquely shaped AWD oil pan. If you are plan to swap this 5.0L into a '60s Mustang or even a Fox Mustang, the pan and oil pump pickup will need to be exchanged.

Late-model hydraulic roller 5.0L Ford engines use a steel cam core and a specific Ford distributor drive gear. Since our original engine came with distributorless ignition, Moore swapped in an earlier distributor, which needed a custom gear compatible with the steel core. Comp Cams sells this composite distributor gear that's compatible with all the different cams, but it's pricey. This gear isn't necessary if you're using an aftermarket cam, because they are generally ground on iron cores—like our cams from Lunati—and don't require a custom gear.

This photo shows Mike concentrating on the bowl area of the heads, but this requires some experience. If you're not familiar with porting, it might be best to leave the work to a professional. Much of the power this engine made on the dyno can attributed to Slover's porting work.

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!

I am wanting to use the smaller cam choice for this set up on my GT40p engine but worried about piston to vale clearance, did they do any thing special or will I be ok?  1988 stock short block gt40p heads


Did you guys try less timing?  Years back when I ran GT40Ps on a carb'd engine combination they wanted 29-31° for max power.  Power dropped beyond that.

Car Craft