302 Ford Engine RHS 168CC Head - Fat 5.0 Power On A Skinny Budget

With all its electronic gizmos, the injected 5.0 Ford engine can look a little intimidating. Get past that, though, and there is a rough-cut stone just waiting to be buffed into a gem. The beauty of this engine is that it tends not to wear out bores or cranks, which means it opens the door to affordable rebuilds and hop-ups-and that's exactly what we are going to do here.

Our starting point is a rock-stock injected long-block from a 1988 5.0 we unloaded from a national core supplier for $150. Although it didn't look like a particularly well-serviced unit, as is often the case, the bores and crank journals were in near-perfect condition. The first step was taking out the galley plugs and cleaning the block. Using Easy-Off oven cleaner from the supermarket, an electric drill, and an assortment of wire brushes, we got the block about as clean as a pro for less than $15. Part of the cleaning exercise was to use some old taps and clean all the threads. (Don't skip this job, as you could end up paying for it later big time.) Once the block was cleaned, the bores were glaze busted using a three-stone, spring-loaded Glaze Buster from NAPA ($27). This and a can of Gunk engine cleaner, used as a lube agent for the glaze busting operation, gave us good-as-new bores for $35. Add a galley plug set and a coat of paint, and the block looked like the photo featured below. The next step was cleaning the pistons and checking the ring grooves for wear. The forged, press-fit pistons Ford uses in the 5.0 are pretty tough; as such, they don't wear to any significant degree. We didn't remove them from the rods for cleaning, since it would likely render the pistons unusable; however, it is important to clean out and lube the piston pin bores of any cleaning agents. Use lacquer thinner and oil for this job, and don't stop until you are absolutely sure all debris and oven cleaner have been removed. At this point, it's time to consider rings. Here we opted for Total Seal gapless rings, and although they are hardly budget items at $230 (from Summit), the two-piece top ring is capable of accommodating minor bore errors better than a stiffer one-piece ring. If your budget is tight, you can find replacement rings for as little as $30, but be aware that cutting costs here is-as our dyno testing has shown-likely to cut output by at least 5 hp and 5 lbs-ft.

Our crank had minimal journal wear, but the amount of out-of-round is more critical than wear. The crank can wear as much as 0.002 inch, and so long as it is round, be good for another 50,000 miles. All our crank needed to restore it to as-new condition was a quick polish, done for the princely sum of $20. With that, a set of bearings ($50, Summit), and a set of Mr. Gasket gaskets ($40, Summit), we were ready to start reassembling the motor. Other than gapping the Total Seal rings per the instructions, nothing out of the ordinary was done during assembly of the bottom end. After inspection, we even used the original stock oil pump.

As far as the cam and lifters go, we're going to stick with stock. Because of some internal deposits we found in the engine at teardown, the stock roller lifters were stripped, cleaned, and rebuilt. The original timing chain, which was far from worn out, and the original timing gears were re-used, and the last bottom end item on the list was a damper. The stock damper was shot, so it was replaced with a Professional Products unit ($68).

HeadsLuck was on our side, as far as the cylinder heads were concerned. Unlike the bores and crank journals, the valve guides can be prone to wear. About 65 percent of the engines I've torn down have guides far past further use (even though the valve stems themselves may be OK). Worn guides drain power-and by a much greater margin than you may at first suspect. If the guides are worn, then the cost of refurbishing the heads is about a half to a third that of new aluminum heads. Ours were good, so they were decarbonized and the valves lapped in to ensure a good seal. After reassembly, a 0.030-inch thick valvespring shim was placed underneath to boost spring force and compensate for any loss from 140,000 miles of use. Once together, the stock EFI heads were bolted on using the stock (but thoroughly cleaned and wire-brushed), head bolts.

Valve TrainStamped steel rail-type rockers are some of the worst parts of a 302. They are high-friction, and suffer greatly with wear unless you know the fix. The problem of wear at the bearing surface of rockers like these has been compounded in the last few years, as zinc phosphates, which act as high-pressure lubes, have been removed from oils for ecological reasons. The solution is Oil Extreme. This stuff works so well it's like pouring in 5 hp.

Dyno TimeAt this point, we have an as-new, though virtually stock, long-block. The cost of this rebuild, including purchase of the core, was about $683. As our dyno wasn't set up for fuel injection, we opted to run a carb and intake, and, while we were at it, test short stock versus long-tube headers. Because we're not running a computer, the distributor had to be mechanical. A Performance Distributors unit ($245) was installed, and you can see the power curves in our graph (Fig 1). The engine, equipped with the Edelbrock Air Gap Performer intake ($230), and a 650-cfm Barry Grant Demon crate-motor carb ($519), cranked out 278 hp and 288 hp with a Victor Jr. intake. As good as those numbers may be, they raise a couple of questions. For convenience' sake, the engine was dyno-tested with a CSR electric water pump. From previous tests, we know this can be worth about 2 hp at 2,500 rpm, and 8 hp at 5,000 rpm. Obviously, the higher the rpm, the more the pump was worth. The second question is how much power the engine would make on the stock fuel injection manifold. Our dyno wasn't set up to test with fuel injection, but a virtually identical engine (with an electric pump) running on a DTS dyno at another shop delivered 255 hp and 313 lbs-ft.

At about the time we started contemplating a serious rebuild, a call from Racing Head Service's cylinder head designer kicked things into high gear. It seems RHS wanted to test a set of prototype small-port heads that targeted a 302-inch displacement, rather than something between stock displacement and the popular 347 stroker builds. The idea was to refine the intake so that it still had good flow, but use a smaller cross-section to boost port velocity and swirl. Taking this approach helps low-speed torque, but has virtually zero negative effect on top-end power for a typical street or street-strip 302.

The engine was reconfigured to facilitate this test. First it was stripped, and the stock pistons were replaced with a set of Ross flat-tops ($519) to accommodate the bigger valves and cam it would normally have. Next, the stock cam was replaced with a COMP 270HR Magnum hydraulic roller. Why this one? Because it's a great street cam when used with a good set of aftermarket heads. It has about 6 degrees less seat duration than the stock 5.0 cam, but is slightly bigger, at 0.050-inch lift. Additionally, this cam lifts the valves almost a tenth of an inch higher, allowing the engine to access the greater high-lift flow an aftermarket head offers.

Other than the cam and piston/rings, the bottom end remained the same as the first test. Because the Ross pistons were lighter than stock, a crank balance job was omitted. Though the lighter piston results in an over-balanced crank, no subsequent modifications are necessary (as long as piston weight is lighter but within 50 grams of the original)

To effectively test cylinder heads, the stock rocker setup has to go. We reconfigured the stock heads with a set of COMP's cost-effective 986 valve springs, and Magnum 1.6:1 rockers. Previous dyno tests showed that as a simple bolt-on, these rockers are worth 8 to 10 horses at peak (and a lot more past peak), over the stock items. When used with an aftermarket set of heads, they really pay off.

With the heads re-sprung, the engine was reassembled using the Air Gap Performer intake and made ready for the dyno. As a reminder, the changes are the pistons, cam, and rockers. Although the pistons had only two valve cutouts instead of four, the compression remained virtually unchanged as the two valve reliefs in the Ross pistons cc'd out the same as the four reliefs in the stock pistons. Back on the dyno, the changes delivered the results seen in Fig 2. As the curves show, the cam and rockers produced some impressive results-even with the stock heads. Notice that the 270 Magnum cam delivered more torque everywhere in the rev range. Although increases were made at the bottom end, the big gains came in the mid-range, where peak torque went from 317 to 349. Additionally, power jumped from 278 to 311 hp. If we include the cost of the pistons, cam, springs, retainers, and rocker setup ($650), we have a totally rebuilt engine for $3,611. Using the original fuel injection and the long-block 0assembly, which will deliver about 40 lbs-ft and 35 hp more than stock, the costs totals approximately $2,862. Whatever induction is chosen, the bottom end is now a prime candidate for a set of heads-and we have some worth telling you about.

Rhs 168cc Pro Action HeadsCurrently, RHS makes a highly functional 180cc intake port head that works great on big-cam 302s (285 advertised duration or more). It is ideal on 331 and 347 engines, though, for both hot street and serious street/strip applications. When talking to Peter Hill, chief head designer for RHS, I asked about the chances of building a smaller-port head for someone sticking with a 302. My guess was such a head, if it worked as well as the 180cc port version, would be a big hit as a primary bolt-on for 302s. Peter promised to think about it, and sure enough, we received a pair of test-ready experimental heads.

At press time, PHR has the only available set of these heads, and here's what tests revealed. First the airflow test (Fig. 3): Here we had a head that was, other than filling in the floor for a 168cc port, identical to the runners on RHS's 180cc head. What difference would this make to the flow? Tests at T&L Engines showed that the smaller port had little to no effect on flow until about 0.500 inch of valve lift. At the maximum lift figures a typical hot street 5.0 would use (about 0.550-inch max), the flow was down barely 2 percent. Also relevant is the fact that at this lift the flow curve was leveling out-a good indication that the port is not too big for the application. For a small and almost irrelevant trade in high-lift flow, the 168cc head achieved a 7 percent increase in port velocity. It was going to be interesting to see how this worked out on the dyno.

Another potentially positive change with these heads was resizing the combustion chamber so that the 5.0's advertised stock 9.2:1 compression ratio can be realized. Most stock cast iron heads have a bigger chamber size than Ford uses to calculate the stock compression ratio, so in reality the stock 9.2:1 figure is seldom reached. For the most part, the smaller chamber results in a compression ratio up to a half-point higher than stock, depending on the original heads' tolerance band. In our case, the RHS heads delivered about 0.2 more compression than the stock heads. Because aluminum heads are good for up to a whole ratio higher before detonation sets in, the small increase by the RHS heads is not a negative consequence, as far as sufficient octane tolerance is concerned. However, such an increase, though small, will help with fuel efficiency.

As for the exhaust port, this flowed well to about .400-inch lift, but leveled off in performance thereafter more quickly than I would have expected. Still, let's not forget that the most important part of the flow capability of a port is generally the first three-quarters of whatever is used for valve lift. If the valve lift used is no more than 0.525 inch, then this leveling off will be of little consequence. This, of course, will all come out in the wash when the dyno test results are completed.

Dyno testing was done at T&L Engine Development, with boss Lloyd McCleary running the show. The engine was baselined, equipped with a set of 1 5/8-inch diameter long-tube headers and Lloyd's 650-cfm dyno-room Holley. Once good, repeatable numbers were established, 168cc RHS heads were swapped in and the engine was retested. Optimal jetting proved to be about two jet sizes larger than the stockers, but since the engine's volumetric efficiency was up by a healthy margin it was expected. The output figures were outstanding-just check out the chart numbers to the right:

Though peak torque and hp figures are up by 25 and 64.2 respectively, this hardly illustrates the complete picture. First, the RHS prototype head made more torque than the stock head everywhere in the rpm range. Second, it hung onto power past peak output, so that at 5,800 rpm it gained more than 80 hp on stock heads. If you're taking a car equipped with these heads to the track, the Real Race average (R/R Ave.) is the rule by which you should measure. This average looks at the output over the rev range used for best performance on the drag strip. Comparison of these numbers shows the RHS heads are up by 36.4 lbs-ft of torque and just shy of 50 hp. That's impressive by any standard, considering a set of heads were simply pulled out of the box and attached. If interested, check the RHS Web site to see when they will be released.

For cost concerns, these heads (one available) will cost around $1,400, which brings the total to $5,011 turnkey in carbureted form, or $4,262 with the original fuel-injection/ignition. Any way you look at it, a newly rebuilt engine 50 lbs lighter and making 150 hp more than stock adds up to an exciting performance increase.

Why The Rhs Pro Action Head Works So WellTo the experienced eye, this RHS head's combustion chamber (shared by the bigger-port versions) is very revealing. First, the intake port blends well into the bottom cut of the valve seat. In the chamber, the wall to the right of the spark plug hole is scalloped away to reduce valve shrouding. The spark plug is positioned nearer the exhaust side of the chamber, which causes the burn to be completed on the hot side before the cool side, by the intake valve. This means the end gases are cooler and less likely to detonate, thus allowing more compression to be safely used. Additionally, the chamber itself is compact in form, and slightly smaller than stock for a small increase in compression. The exhaust seat has a generous radius under it, and the short side is hand-blended into the cast surface of the port floor. This is good for flow, and in all, looks to be an effective chamber form.