Ford Capri AFR Cylinder Head - King Capri

To A 5-liter owner, getting a set of aluminum heads is like hitting the lottery. The factory chunks of cast iron don't flow diddly, and that's a big problem if you're trying to make horsepower. Thankfully, aluminum heads are plentiful and affordable. Unlike the modular powerplants, which have pretty good heads in stock form, the 302 engines from 1979-95 weren't big breathers, so one of the keys to unlocking power comes from swapping the heads.

Knowing this, 5.0 owners will normally go for a set of aftermarket heads, of which dozens are available. Aftermarket aluminum casts prove beneficial because they save weight and increase airflow to the engine. For around $1,200, anyone can increase performance of an otherwise stock 5.0, and with a few extra bolt-ons, the increase can be doubled. That's the point we're trying to prove in this article.

Often, owners subscribe to the "bigger-is-better" theory, but this just doesn't work when trying to select the most efficient set of heads for a mostly stock 302. It's far more important to select heads that have intake and exhaust ports (and valves) sized for your intake, cam, exhaust, and gearing, or the combination won't be efficient. In many applications, smaller ports create better airflow velocity in the low and mid-lift range. This helps fill the cylinders, which translates into great torque and excellent throttle response. Some will still want the big flow numbers up high, at 0.600-inch lift, but for most street/strip applications, you'll see better results when you focus on average power.

To that end, we decided to swap heads on the '85 Capri we've been fooling with. In the past two issues, we've taken the mildly modded 302 and added a Weiand Stealth intake and Demon 575-cfm carb, an S&B free-flowing air filter, and a Holley fuel pump. We also added a Lunati cam (PN 510A2LUN) with 0.525-inch lift and Comp's 1.6 Magnum rockers. For our effort, we were rewarded with gains of almost 50 rwhp, from 207 to 255. Now it's time to swing for the fences.

We originally selected Air Flow Research's popular 165cc heads for this article, but the folks at AFR turned us on to their latest 165 Competition Package heads with 1.90- and 1.60-inch valves. The Comp Package uses the standard 165 casts, albeit with a different porting profile.

"We run a different porting program with a different shape in order to flow more air," says Rick Sperling of AFR. "[The program] takes a few more hours to run, but it picks up 7-10 cfm across the board, from 0.200- to 0.600-inch lift on the intake and exhaust.

"The Comp heads are for the guy who can't use a 185cc head with the larger 2.02-inch valves because they would hit the pistons in a stock short-block. For the size, these heads offer excellent flow with small valves and ports, and we've seen them make 10-12 hp over our standard 165s."

Swapping heads on a 302 is not difficult, but there are things you should know. First and foremost, you'll need a set of gaskets. We used Fel-Pro 8548 head gaskets, as well as new head bolts from ARP in our 130,000-mile engine. While AFR offers the heads with pedestal rocker mounts, we ordered ours with stud mounts because of the the Magnum rockers we're using. The stud-mount heads come with pushrod guideplates, and this requires hardened pushrods, which we got from Manley (PN 25627-16). We also slipped in a new set of hydraulic roller lifters from Comp Cams because the stock lifters looked beat up

If we hit it right, the package would produce awesome power from idle to redline. While we didn't want to make any predictions, we were secretly hoping the 302 would eclipse the 300-rwhp mark.

With parts in hand, Glen Knell of Crazy Horse Racing worked with us on the 302 from morning to evening. In that time, we had the heads and most of the components bolted to the 302. At this time, we also realized the 302 was not equipped with stock '85 heads, but a set of E7TE heads that had the emission bumps removed from the exhaust ports. The following day, we buttoned up the engine, added the coolant, fired the engine, and checked for leaks. All seemed well, so we strapped the Mercury to the Dynojet to get the results.