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Greg Dillon

Active Member
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rollerrocker11mv.jpg
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I hope this works-here are some pictures of a pair of Ford Motorsports roller rocker arms on one of my 0-320-H2AD cylinders. The stock stud is removed and replaced with an Allen head bolt. Stock Lycoming shims are used to set lifter preload. Notice the offset on the exhaust valve rocker to get the valve rotator to spin. It's more apparent with the roller rocker than with the stock Ford (Lycoming) stamped steel rocker. Oiling is thru a drilled passage above the pushrod cup and a stream of oil is directed to a reservoir leading to the roller tip and pivot. It appears that valve cover clearance will not be an issue as installed height is the same on both stamped and aluminum rockers. Definitive testing of clearances will have to wait until I install the overhauled cylinders on the engine. So far so good! Greg RV9A N4603X (res.)
 
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osxuser said:
Not centering up on the right valve stem might be a problem.
Click to expand...
The right valve is the exhaust- the stem has a rotator cap and the offset sets up a spinning motion when the valve is actuated. The offset is more apparent with the roller rocker than with the stock stamped rocker.
 
Sincere Question.....

Why?

I have a hard time undertanding the benefit of theses parts at the RPM of an aircraft engine.

I fully understand the use in engines where there is high lift, rapid opening ramp profiles, and high RPM, but...I do not see the benefit on this application.

What are the goals?
 
Well I have to comment here... Roller rockers do reduce friction and increase longevity but in this case I can tell you for sure there isn't going to be any valve rotation happening. Roller tip rockers virtually eliminate this from happening. If you can get that exhaust valve rocker more in line would be more acceptable. All you will get with it like this Greg is a side load on the valve and guide. Don?t take this wrong, I?m all for your mod here Greg. I have personally used these exact Motorsport rockers on my Fox bodied Mustangs. Here's a shot of my XP-360 rockers... as you can see no retro fitting gonna be happening for this FORD die hard :( Oh well. If it makes you feel any better I did get the XP-360 Plus mainly because it uses the same 1985 Mustang 5.0 hydraulic roller lifter set-up. IMO they should have been using this technology in aircraft long before cars. But our good old government and their strict emissions laws is obviously what forces this kind of engineering to be used in our vehicles. Its funny how it takes 20 years for them to implement its use in aircraft. Im sure it wont be long before we will be forced to use catalytic converters on GA craft. But you didnt hear that from me! ;) Rock on Greg with your adaptation! I'm all for it!

-Jeff

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I've been running roller rockers on my O-320 since 1995. The biggest benefit for roller rocker arms is to reduce valve guide wear. They reduce the side load on the valve stem.
 
Mel dont you mean parallel to the axis as opposed to side load? I agree they reduce the load vertically but side load in this case would be fore and aft. With the rocker hangin off center line to the left like shown in his picture is not good for neither the rocker or valve/guide.
 
Mel- I finally realized what you meant. Yes you are correct, side load is side load regardless of direction. However the rocker does need to be running on center of the stem.

-Jeff
 
I wasn't refering to this application particularly. My roller rockers are centered on the valve. My reference to side loading is that when the standard rocker arm puches the valve down, it also side loads the valve stem because it is pushing slightly forward (away from the pushrod).
And yes, I do agree that the rocker should be centered on the valve stem regardless.
 
As I understand it, roller rockers are used more to allow more radical camshaft lobes (with fast rising, high lobes) that cause non-rocker lifters to catch or wear quickly/unevenly at the high rpm the camshafts are designed for.

At the slow rpm window of Lycs, the rollers are probably not needed; Id pick the lightest rockers avilable instead.
 
Mike that is one of the benifits but not the most important. Its all about reduction of friction regardless of RPM. As a matter of fact when FORD implemented the roller tappets in 85 they were being used on camshafts that were of a "Marine" grind and were low RPM, high torque profiles that operated best around 1500~2500 RPM.

-Jeff
 
My sense of curiousity makes me wonder what brand of rockers you are running Mel? I'd like to see some pictures and stuff if you've got any.
 
My roller rockers were manufactured by Ken Hatfield Enterprises, in Oregon. I don't know if he is still in business. Haven't heard anything for quite some time. They are machined out of 7075-T6 with needle bearings on the rocker shaft. Mine have worked beautifully for over 700 hrs.
 
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