Rocker arms are a pretty critical part of your valve train – linking your intake and exhaust valves to your camshaft. However, for more street enthusiasts, they don’t have the same sex appeal as big-ticket items such as cylinder heads, camshafts, or power adders. In the case of our 1993 Ford Mustang — equipped with AFR heads and intake — along with the stock, yes stock, rocker arms, they were proving to be a major power prevention device. With the help of Harland Sharp, we aimed to turn around our under performing engine with their innovative adjustable pedestal-mount rocker arms.
One of the first upgrades most people do to their Fox body Mustang — after exhaust — is installing a set of roller rockers to reduce friction and increase horsepower. However, with our 1993 Ford Mustang, we had taken a slightly different route by installing AFR 165cc heads, an Edelbrock intake, and a Ford Motorsports E303 cam, with the STOCK rocker arms. Your author did not have in the budget to do an entire upgrade to the valve train at the time we installed the heads, which is why the stock ones were used. Our Mustang is a street-oriented performance ride that should run low 12’s in the quarter mile on slicks.
Now, at the time, it was obvious that using stock rocker arms was a mistake. Power robbing, flexing, and friction-inducing parts are never a good choice for a performance engine. However, the siren call of the bank account rung louder than my right foot, and for this one time, perhaps the best choice for the long run was made.
Now, here was the problem — to use the stock rocker arms, we had to go with bolt-down-style AFR 165cc heads rather than the stud-mount AFRs. Now that we were converting to rocker arms with roller tips and a roller body, we also wanted to install adjustable rocker arms for not only the adjustment capability, but also to give us leeway to install a different camshaft down the road. Here, we ran into a road block that was only solved by a very innovate solution from Harland Sharp.
Harland to the Rescue – Adjustable Bolt-Down Rockers
This article started with us calling the good folks at Harland Sharp, who have been building rocker arms for only 45 years. They don’t make anything but rocker arms. When you spend over 4 decades building the same thing, you’re probably destined to be extremely good at it. Now, they do make a variety of rocker arms beyond the ones just reviewed in this story.
Let’s start by reviewing the problems with the stock rocker arms. First, the rocker arms are made of cheap cast steel, so while they are good for stock-type engines, they are not strong enough for the rapid ramp of an aftermarket camshaft. Thus, the rocker arms tend to flex, losing out on valuable lift at the valve, reducing power.
Second, the rocker arms feature a friction-inducing pivot ball and non-needle rocker tip, producing wear and increased loading at the rocker. Again, fine for a stock camshaft and non-performance engine. However, with the increased RPM potential of the juiced 302 we had, with the AFR heads, and with the higher lift of the E303 camshaft, the stock cast rockers were being asked to do things that they were never designed for by Ford.
When it came time to select our aftermarket rockers, we told Randy Becker of Harland Sharp that we are racing on a budget, and needed something that works right and didn’t break our wallet. What we really needed was a set or rockers that could go on these AFR 165’s with no machining needed, but could also support some pretty serious spring pressure for the new camshaft we were planning. Most bolt-down rockers would fold under these requirements.
Rocker Arm Choices
You see, bolt-down, or pedestal mount rockers, are the most common rocker arm style from the factory. A single 5/16-inch bolt holds down the rocker assembly. It is a simple upgrade to bolt on a set of pedestal mount roller rockers, while upgrading to stud mount would require head removal and machining. However, a 5/16-inch bolt isn’t a very strong arrangement.
Stud Mount rockers are the most common type of rocker arms found on performance engines, as they pivot on a 3/8-inch or 7/16-inch stud mounted into the cylinder head. Stud mount rockers are generally more stable than pedestal mount and you have a lot more adjustment to get the valve train aligned correctly.
Finally, shaft mount rocker arms are superior for racing and high performance applications. Shaft Mount rockers have a mounting assembly which is bolted down permanently to the cylinder head, and then two, or more, rocker arms are ganged together on a common shaft. They are great, but out of our budget.
Since we already had pedestal mount-style heads, we wanted to keep them. Our budget screamed “bolt-down” rockers, but we didn’t want to scrimp now and end up with bent or damaged rockers by being cheap.
The answer to our problem – Harland Sharp’s “Heavy Duty” Adjustable Pedestal Shafts. With a full roller body, these Heavy Duty series rockers featured a linked shaft between the two adjoining rocker arms, allowing them to support up to 350 lbs of spring pressure with the measly 5/16-inch pedestal mount bolt. List under part# SH40076A, these were destined to replace the stock arms without any machine work. Essentially, these are poor-man shaft rockers, but with no real compromises for hardcore street engines.
Key features include:
- Cage-guided needle Bearings
- 3/4-inch Diameter Rocker Shafts
- 7/16-inch Internal Oil Adjusters
- All Necessary Hardware
With a hotter hydraulic roller in our plans, Harland told us their rockers wouldn’t break a sweat. “This rocker system is great for most hydraulic roller cams, we can handle 350 lbs of open pressure before we run into any problems,” explained Becker. “If you have more spring pressure than this, you should consider installing stud-mount rocker studs and guide plates. These are perfect for the budget-minded guy who doesn’t want to deal with additional machining to their heads.”
Although available in both 1.6, and 1.7 rocker ratios, we chose the 1.6 ratio to help minimize concerns about piston to valve clearance with a larger ratio rocker arm.
What we were looking for with our Harland Rocker arm swap? Simple. More horsepower, adjustability, and less power-robbing friction. What we didn’t have was “previous” dyno numbers. Again, that old budget thing. Our power desires exceeded our financial resources, but we decided to do this right. After the full installation, we would do a dyno test to get a baseline for future modifications and to see how much power we would produce. Of course, we would be able to use the best detection system for power – our butts, and for our seat of the pants test before and after, we promise you a full report.
When the Harland Sharp Box came, it was almost like Christmas. We couldn’t wait for the weekend to install this much-needed roller rockers. As detailed above, the rockers we received were 1.6:1 ratio, (part number S40076A) aluminum, pedestal mount rockers.
Install Part One: Removal
First step is to disconnect the battery. It is always a good idea to disconnect it when working under the hood or on anything electrical. The 10 mm wrench should be the right size to remove the battery cables, though aftermarket battery cables can have different size bolts. Next, remove the intake tube from the air meter to the throttle body, loosening the clamps at each end. Once the clamps are loosened, it should slide out with a little twist. The throttle cable can be removed by snapping it off the ball on the throttle body.
The passenger side valve cover can now be removed. Use a ratchet, an extension, and a 10mm socket to remove the 6 bolts that hold the valve cover on. Here you can see the location of the bolts that hold the valve cover in place. Once you have all the bolts out, just roll the cover towards you and it should come right out. On the driver’s side, there are two fittings on the bottom of the Edelbrock intake that need to be removed with the 1/2-inch wrench. Remove the 6, 10 mm bolts that hold the valve cover on and it should roll towards you to come out. Now you can see the stock rockers with the valve cover removed, and can remove them.
Part 2: Replacing the Rockers
Before installing the new rockers, Harland Sharp recommends that we coat the roller tip that touches the end of the valve and the ball tip where the push rod sits. This will help the life of the rocker arm. We actually took their advice and let the rocker arms soak in oil for 30 minutes to help get oil into the needle bearings on the tip and rocker body.
Here you can see the Harland Sharp rocker compared to the stock rocker arm on the left. You can see the wear marks on the stock rocker tip due to the high lift camshaft.
Now it was time to install the rockers. Here are some tips and tricks:
- With aluminum heads you should use anti-seize on each of the 5/16-inch pedestal mount bolts. We did.
- Before installing the rocker arm, make sure the adjustment screw is backed out to make sure you don’t cause any damage when tightening down the rocker arms.
- Make sure you adjust the rocker arms down in the correct order. The simplest and easiest method is to do the exhaust rocker when the intake is almost closed, and to do the exhaust rocker with the exhaust is starting to open.
After puting anti-seize on the threads, we slide the new 5/16 bolt Harland supplies through the rocker arm, and slide the spacer/mount on the bolt with the larger diameter being closest to the cylinder head. The rocker arms will be installed in pairs. Tighten each rocker arm in the set evenly so they do not bind.
To adjust the rockers, you will tighten the 1/8-inch allen head screw until you feel tension on the push rod. This is zero lash without pre-load. You should still be able to slightly spin the push rod here.
When you feel tension, you will give it a 1/2 turn more, and Becker recommends to not go more than 1/2 turn past zero lash. Then, use the 7/16-inch wrench to tighten the lock nut and at the same time holding the adjustment screw in place with the allen wrench. When complete, tighten the locking adjuster in place to 20 ft-lbs.
What to do for Stock or Aftermarket Valve Covers
Now that the rocker arms are all installed, it’s time to install the valve covers. Here you will be thrown for the same loop as all 5.0 Mustang owners are when they first try to bolt down valve covers after installing rocker arms. To get the stock valve covers to clear the roller rocker arms, you will need to do some grinding on the extra material around the oil fill neck, and sometimes, on the supporting ribs inside the stock covers. This will be a trial and error procedure until you remove enough material to clear.
These are the fugly stock valve covers. Since we didn’t want to do all of that grinding, we elected to buy some Ford Racing tall valve covers.
We decided to install the tall Ford valve covers instead. With the taller valve covers, an intake spacer will need to be installed. We installed the new spacer, and then finished up installing the valve covers and the intake manifold.
This is our completed installation below before we installed the intake and got ready for the dyno test. As you can see, the new valve covers look much nicer.
Due to time constraints, budget, and a busy schedule, we never got the Mustang on the dyno prior to the rocker arm installation. Though, after the first test drive we could tell a seats of the pants improvement – not only in just power but also in smoothness and valve train noise. The car pulled harder on the seat-of-my-pants dyno, and it even seemed to rev smoother and idle better. Although the power increase is estimated at around 10 horsepower, it could likely be greater due to the greater camshaft lift obtained at the valve due to the fact that the Harland rockers won’t flex like the stamped stock rockers.
We did want to do an after dyno test, both as a baseline, and to verify that our Harland Sharp equipped engine was making good power. For the dyno session, we took the car to Chris Lovett at Wichita Dyno. It is not unusual to see Lovett at the dyno for over 15 hours a day and sometimes seven days a week.
Here is our 302 ready for the dyno testing.
After the first attempt on the dyno, Chris shut it down early because the wide band was reading lean. Not good. That is why dyno testing is so critical and we gave ourselves a few demerit points for not doing it earlier. After messing around with fuel pressure, we were unable to figure it out until Chris determined we had a dirty mass air meter.
We then cleaned the air meter and backed the fuel pressure off and made another pull. The car still had too much fuel pressure — so we backed it off more. Without any aftermarket tuning chip, we were limited to fuel pressure to determine the optimum air fuel ratio, not a good situation.
Finally, we were able to lean it out enough to get a good run, and made 293.5 rear wheel horsepower and 331.6 ft lbs of torque, with a peak power reading around 5,200 rpm. This was a pretty impressive number, and we have no doubt that the Harland roller rocker arms have not only completed our top end assembly, but added to our horsepower gains as well.
We realize not all of you are in the same boat as we are – with stock rocker arms. Thus, it’s good to know that Harland Sharp makes not only these killer Heavy Duty adjustable pedestal mount rocker arms, but also conventional stud-mount and shaft rockers as well.
Over the 45 years, Harland Sharp has developed three different “grades” of rocker arms – the Original Series, Heavy Duty Series, and the Diamond Series. The Original Series is their current standard rocker arm, a great choice for a performance engine. Heavy Duty versions include a wider body for increased strength, longevity, and higher spring pressures. Finally, we come to the Diamond Series, which is a lighter weight rocker arm. Over 100 grams has been removed from the body while keep the same durability and strength, giving you increased RPM potential.
Overall, we couldn’t be more pleased with our rocker arm install and testing. We made great power, the installation went smoothly, and now we’re confident that the valve train under our valve covers is as good looking and functional as the Mustang is on the outside.