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Installation

Rocker Arm!
The stock die-stamped rocker arm (left) and the new Omega aluminum rocker (right). Stock rockers are notoriously inaccurate and may vary in ratio with the set.

We obtained a good used set of 1.72:1 ratio Omega roller rockers for about $100. They will yeild a 7.4% increase in lift (from 0.444" to 0.472"). Combined with the reduced friction of the roller bearing fulcrum and roller tips should free up some horsepower! As the photo’s show they are a nice anodized blue color and much beefier (read “stronger”) than the stock, stamped steel, rockers.

They include bolts and pedestals and are identical to stud mount rockers EXCEPT for the size of the hole in the trunion- it is sized to fit the stock pedestal bolts (5/16”) and not a 3/8” or 7/16” stud, so they cannot be used in that fashion. Many people have made the mistake of simply bolting down a set of new pedestal rockers thinking that the since the architecture is nonadjustable there is no need to worry about correct rocker arm geometry. This is incorrect. You MUST check for proper installation and either shim the pedestals or install longer pushrods to insure proper alignment and prevent premature valve guide wear! It is actually quite simple and all you need is a torque wrench. We'll take you through it...

  • To get to the rockers arms the valve covers need to come off. On a 5.0L EFI engine this means removing the upper intake manifold. Start by removing the air inlet tube.

  • Both the throttle cable and transmission TV cable (on auto equipped cars) simply can be pried loose of the throttle body. Then remove the two bolts holding the cable bracket to the throttle body (10mm socket).

  • Disconnect the coolant lines for the EGR spacer behind the throttle body. Also disconnect the valve-cover to throttle body breather hose.

  • Disconnect the IAC, TPS and EGR sensor connectors. All of the electrical connectors have a unique shape so don’t worry about reconnecting them incorrectly.

  • Disconnect the two small vacuum lines to the EGR valve and the fuel pressure regulator.

  • Remove the six upper to lower manifold bolts (1/2” socket w/ 6” extension). Two of the bolts are under the intake plaque (on a stock intake).

  • There are several vacuum connections underneath the upper manifold (PCV, brake booster, evap. canister, and AIR valve) that can be tackled after you get the manifold loose. Then remove the upper intake assembly from the engine bay.

  • Remove the valve covers. (Cleaning the area around the valve covers is a good idea before unbolting the valve covers. Grab that shop vac and clean up in the valleys between the valve covers and the lower intake. Place a rag over the lower intake to avoid getting junk into the engine.)

  • Unbolt the stock rockers and remove them from the heads. Clean all the metal guides that go underneath two adjacent rockers as it will be reused (at least w/ the Omegas). Once the old rockers are out it is time to bolt in the new ones.
    Rocker Arm!
  • Pedestal mount rocker arms have a 5/16" bolt passing down through the pedestal and into the head. The Omegas are assembled two rockers at a time placing the pedestals in the stock guide piece (see photo.) Put a pushrod in place and then lightly assemble rocker arms on the heads.

  • Start by setting the the #1 piston at top dead center on the compression stroke. You can confirm this by checking to see if the rotor is pointing directly at the #1 spark plug terminal on the distributor cap. If it is not, rotate the crankshaft until it is. If the distributor is out you can remove the #1 spark plug, and rotate the engine until you feel air rushing out of the #1 spark plug hole, indicating that the #1 piston is coming up on the compression stroke. Then observe the timing marks on the harmonic damper and continue rotating the crankshaft until the 0 degree, or TDC, mark lines up with the pointer. At that point in crankshaft (and camshaft) rotation, both the intake and exhaust valves will be closed and the cam will be on the base circle.

  • Working on the #1 piston, slowly spin the pushrod, of the intake rocker, between two fingers while you tighten the 5/16" bolt with your other hand. When it becomes difficult to spin the pushrod, indicating that all clearances have been taken up, torque the 5/16" bolt to 20 ft-lb. If more than one full turn of the bolt is required to achieve the torque setting, you will need to shim the pedestals. Unlike a stud-mount rocker, the only adjustment possible is adding or subtracting shims under the pedestal.
    Rocker Arm!
    Pedestal shims.

    Shimming: Back off the bolt, add a .015” - .020” inch shim under the pedestal, and try it again. Keep adding shims until the torque applied to the bolt reaches 20 ft-lb with between one-half and one full turn of the bolt after the pushrod stops turning. If however the pedestal bolt reaches 20 ft-lb and the pushrod can still be easily rotated, the pushrod is too short and must be replaced with a longer one.

  • Repeat the procedure for the exhaust side. Then move the crank counterclockwise so that the rotor is pointing at the next cylinder in the firing order and adjust the rocker arms for that cylinder. Continue through the firing order until all rockers are adjusted.

  • With the new rockers bolted down the valve covers and upper intake were reinstalled with fresh gaskets. Now is a good time to check and replace any cracked or old vacuum hoses. It is amazing how many times we hear people blaming a new modification on drive-ability or performance problems, yet the real problem was a vacuum leak.
BeforeRocker Arm!
After
Rocker Arm!

 

Results
Take a look at the time slips and see for yourself. We were shocked! We ran a 14.261 seconds before the rockers and 14.357 seconds after… In other words the effects of the rockers were NADA! ZIP! ZILCH! In actuality we lost a little bit.

Both runs were made at Sacramento raceway, about a month apart. We compared the two timeslips with identical 60ft times to draw our conclusions. The track conditions on the "before" pass were much better (cool, dry air) than the "after" pass, however judging by the same 97.4 mph, we don't think the weather had a huge effect on the results.

Before
Stock 1.6:1 rockers
Radials
Cool/Dry Air
After
1.72:1 roller rockers
Radials
Humid/Warmer air temp

The horsepower is best represented by the mph and they are within .014 mph of each other. So, 6 hours of driveway labor, $100 for rockers, $10 for shims and $15 for gaskets. All that and no increase in power with even a possible slight decrease.

After lots of discussion and debate we have concluded that with identical weather there may be a small improvement, but not much. The stock heads increase flow about 15cfm between .400” and .500” lift, but we are only increasing the lift by .033” so perhaps the increased lift is not supported by the heads, or is not enough to overcome the poor flowing stock intake/exhast ports.

We also suspect that perhaps the stock valve springs are worn and cannot handle the additional lift. This is an important point to consider when going to higher ratio rockers, especially with a high-lift camshaft. You must check for adequate spring pressure, and ensure there is no coil bind.

Bottom Line
We didn't gain anything by changing to 1.72:1 roller rockers on our stock 5.0L EFI engine.
Put these rockers on an aftermarket head, or with a different cam, and you may see an nice increase. If you really want to optimize your combination, you can even try installing higher ratio rockers on just the intake or exhaust side (a common trick for engines with power adders.) The conclusion is it is one of those modifications that simply must be tested on your given combination to see if there are any gains in power. F/M



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