I have two different Scorpion Roller rocker arms along with a .650" short pedestal and a .750" long pedestal for testing.
The long .750" pedestal part number is SCP 516 PEDL -1
I will test the Scorpion BBF rocker arm later.
The other rocker arm is the one used for the Ford 300 six and is the test rocker shown below.
I am testing on a Promaxx head with a 4.910" exhaust valve.
It is a 1.60" diameter valve sitting on a seat insert same as the CNC ported head.
I am using a .040" thick washer under the pedestal in place of the .040" thick "U" channel.
Here is what the setup looks like.
Setup1.jpg
The first combination tested is the .750" pedestal at .500" valve lift.
The pattern looks centered
Tall Pedestal Long Valve 1.jpg
Next test was with the .650" pedestal at .500" valve lift.
The pattern is off center towards the rocker stud.
Short Pedestal Long Valve 1.jpg
The next test involved shortening the valve height by .160" to simulate the 4.750" long stock valves.
The short .650" pedestal was used.
This test represents the Scorpion 1059 rocker set as it is used on the stock replacement head with stock valves at a .450" valve lift.
The pattern was slightly off center away from the rocker stud but within reason.
If the 4.750" stock valves were replaced with the pre-1985, 4.810" long stock valves, the pattern would be centered, and you would also gain valve lift clearance.
Short Pedestal Short Valve 1.jpg
In conclusion, use the long .750" pedestal with the 4.910" valve and the standard .650" pedestal with the stock length 4.750" valve.
If the 4.750" stock valves were replaced with the pre-1985, 4.810" long stock valves, the pattern would be centered.
The long .750" pedestal part number is SCP 516 PEDL -1
What I highly recommend based on these results is, if you are rebuilding a 1985, 1986 and later EFI head with stock diameter valves, replace all the valves with the 1984 and earlier 4.810" long valves.
If you are ordering the Promaxx stock replacement head, see if you can get it with the longer 4.810" stock valves.
If not then order the stock replacement head without valves and install your own 4.810" long stock diameter valves.
This will solve the .450" valve lift limitation and improve the rocker arm geometry when using the Scorpion Roller rockers.
Further Scorpion rocker arm testing:
At the height of the valve stem, the stem center to rocker stud center measures 1.585"
The Scorpion roller tip center to trunnion center measures close to 1.62" so the rocker arm has to sit lower than ideal to center the roller tip on the valve stem.
The ideal position is where the line through the trunnion center to the roller tip center is 90 degrees to the valve stem when the rocker arm is at 1/2 the total valve lift.
Using the .750" pedestal, the rocker arm sits .350" lower than the ideal and is why there is such a wide pattern.
So I decided to jack the Scorpion rocker arm up .350" and look at the pattern.
Raised Scorpion Rocker 1.jpg
After running the raised rocker through a .500" valve lift as before this is the pattern.
You can see that the pattern is a little off center away from the rocker stud because the rocker arm is about .035" longer than the stud to valve stem spacing.
But notice how much thinner the pattern is than before.
When the rocker arm can sit at the ideal position, the rocker tip travel is minimized.
Raised Scorpion Pattern 1.jpg
Here is the Harland Sharp roller rocker arm set at the ideal height.
It has a roller tip center to trunnion center very close to 1.600""
Once again the stud to valve stem spacing is 1.585"
You want the rocker arm length about 1/2 the travel length more than the stud to valve stem spacing so the travel will center on the valve stem.
The HS rocker is as close to ideal for this setup as you can get.
HS Rocker Arm 1.jpg
This is the pattern as the rocker went through a .500" valve lift as before.
The pattern is thin and centered.
HS Rocker Pattern 1.jpg
This is the stud I used with the Harland Sharp rocker arm.
It is 2.3" long which allows the set screw in the locking nut to sit just below level.
If you subtract the .135" thickness of the pushrod guide plates, the rocker studs can still be over 2.00" in length without machining the stud towers shorter.
My testing with this head shows that the Promaxx head does not need the stud towers machined shorter when using the Harland Sharp rocker arms.
For reference on another cylinder head, I ran a straight edge from the top of the valve stem out over the stud tower. It measured 1.360" above the tower.
Stud Length 1.jpg
This test is with the Scorpion BBF roller rocker arm on the longer .750" pedestal.
BBF Rocker Arm 1.jpg
The BBF rocker was run through a .500" valve lift and created the following pattern.
As you can see the BBF rocker arm is too short, and pattern has a large offset towards the rocker stud.
The hope was, if the BBF rocker had worked, there would have been the option to use the adjustable version for use with a solid lifter cam.
BBF Pattern 1.jpg
This is the Scorpion Jeep I6 1.6 ratio, non- adjustable rocker arm set at a height where the pattern is centered on the valve stem tip.
I had the use the .610"/.500" pedestal shown above to get the correct height.
The .040" thick washer under the pedestal is the same thickness as the "U" channel.
This is a Promaxx cylinder head with 1.94"/1.60" SBC valves
Because the rocker arm is long, it sits at an extreme angle.
The 1.340" diameter stock retainer is set down .050" and still touches the bottom side of the rocker arm.
A beehive spring and retainer should solve the clearance problem.
Scorpion Jeep Rocker 1.jpg
At .500" valve lift the pattern is centered and is about .160" wide
Scorpion Jeep Pattern 1.jpg
At .500" valve lift the rocker arm has still not passed the 90 degree position with the valve stem.
In this position, maximum spring pressure occurs when the rocker roller tip is furthest from the center of the valve stem center.
Scorpion Jeep Open Angle 1.jpg
Next step on the Jeep Scorpion rocker arm is to raise the rocker arm so that it is 90 degrees to the valve stem when it is at half valve lift or .250" in this case.
I used the .757"/.650" pedestal shown above and an additional .330" of spacers along with the .040" washer to get the correct height.
Scorpion jeep Half Travel 1.jpg
The resulting pattern is only .050" wide and the center of the pattern is .050" from the center of the valve stem tip.
In this case, even though the pattern is offset, the roller tip is closest to the center of the valve stem center when the valve is open at maximum valve spring pressure.
Secondly there is a lot of clearance from the retainer to the bottom of the rocker arm.
Scorpion Short Travel pattern 1.jpg
I am also looking at the Harland Sharp Jeep I6 1.6 ratio pedestal mount roller rocker arms as a possibility for the Ford 300 six.
The Harland Sharp Jeep roller rocker arms come in adjustable and non-adjustable versions.
The adjustable rockers would open up the use of solid lifter cams with pedestal mount rockers as well as making hydraulic lifter adjustments much easier.
Here is what I found.
These are the adjustable Harland Sharp Jeep I6 1.6 ratio pedestal mount roller rocker arms.
They come with a dowel pin between them so the "U" channels are not needed to maintain rocker alignment on the valve stems.
As you can see the HS pedestals are different than the Scorpion pedestals.
Once again a Promaxx head with 1.94"/1.60" SBC valve is being used for testing.
HS Rockers 1.jpg
HS Rockers Installed 1.jpg
The Harland Sharp rockers are long and sit very low in order to get a pattern centered on the valve stem tip.
HS Rockers sit low 1.jpg
At .500" valve lift the pattern is centered and is about .210" wide.
HS rockers long travel 1.jpg
Next step on the HS Jeep rocker arm is to raise the rocker arm so that it is 90 degrees to the valve stem when it is at half valve lift or .250" in this case.
HS Jeep Rocker sits high 1.jpg
The resulting pattern is .050" wide and the center of the pattern is .075" from the center of the valve stem.
HS Jeep Rocker sits high pattern 1.jpg
Side Notes;
Scorpion has 5 different height pedestals.
Scorpion Pedestals 1.jpg
Reserved #1
Reserved #2
Reserved #3