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Roller rockers for Lycomings....

rvpilot

Well Known Member
A while back there was some activity on roller rockers for our Lycomings. I have checked both sources listed in these posts to no avail. Anyone got some current information on any roller rockers that may be available?
This has become of particular interest to me after seeing the valve guide wear on my engine. As I understand from Mel in these older posts, the ones on his engine have virtually stopped this problem.
Thanks!
 
My engine has the rollers. Running fine but not much time yet.

It is my understanding they are not a retrofit item for older engines - at least not the Lycoming system. There was a roller up grade some years ago but I don't know if anything ever came of it.
 
We'd do it

For the decreased side load on the guide, we'd do it. (Parallel-valve O-360)

Price would have to be right, of course. I thought I had read that there was an automotive roller rocker that actually fit (Chevy, perhaps?)
 
I'm running steel heat treated roller rockers on my Lyco and love them. :) We were going to put them in production last year, not enough interest it seemed... parallel valve Lycos only.
 
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I have a couple of sets of aluminum roller rockers that I have had made. They have adjustable cups and use a tapered pushrod to increase valve lift. Have not tested them yet.

FWIW hi-chrome guides will eliminate having to comply with SB 388, since they significantly reduce guide wear. So the roller rockers are of little benefit unless you're doing what I'm doing.
 
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Lycoming Angle Valve Roller Rockers

I am currently dyno testing a roller rocker arm for angle valve lycoming engines. Will hopefully be through dyno in 30 to 60 days and be field testing. These will be aluminum with steel roller tip fully oiled. Ratio is 1.4 to one and will clear 10 to one pistons. They will require shorter pushrods (will be supplied in kit) and will be adjustable.

anticipate kit cost to be around 1800 for 4cylinder and 2500 for six cylinder.
Would appreciate feed back on interest.

Thanks
 
Even running the Roller Rockers in the Lyco, we Cryo'ed all wear parts in the heads for long lasting durability. :cool:
 
Roller rockers

Hey RocketBob - I just had to pull a cylinder on my O-360 after 270 hours for a worn exhaust valve guide. ECI cylinders with the high chrome guides.

While you are correct (legally) that SB388C doesn't apply to ECI cylinders with high chrome guides, I find my guides wearing nevertheless.

Before I pulled the cylinder, I checked the guide with a dial bore gauge and found it worn only in the vertical axis i.e. oval shaped. Horizontally there was no measureable wear. It seems this could only have happened if the rocker was side loading the valve.

So, I'd be very much interested in roller rockers is anyone has a solution. In particular, I think steel is the way to go because of the potential for fatigue issues. Rockers go through stress cycles so fast that aluminum scares me in the long term...

For a good, simple reference on fatigue limits of aluminum vs. steel, check out this wiki -

https://en.wikipedia.org/wiki/Fatigue_limit

Anyone have a source for steel shaft type rockers for the O-360?

Thanks -

John
 
Welcome to VAF, John!

Are you sure you have enough oil flow up there? It is a tiny trade off corner with oil flow, coking on the stem, (sticking), wear, and valve rotation. It all comes down to being close to too hot. Positive valve rotators will be needed with roller tips. Good luck with the adventure.
 
It was my understanding from the automotive world that side loading was a product of poor geometry, not the interface method (i.e. proper geometry fixes side load regardless or roller or std interface). When I set up custom engines, I would use adjustable push rods to set the proper geometry of the valve train, then make pushrods based upon that desired length. Unfortunately this can only be done with adjustable rockers, which the Lycomings don't have.

You might be able to adjust geometry by swapping different rockers/pushrod combinations to get a desired outcome. I would expect that tolerances on rocker machining in the Lcoming's to be loose, but don't know that. I have never done geometry settings on standard rockers, so not sure on the correct measurement approach. It was easily done with sharpie marker with roller rockers.

Larry
 
Ken Hatfield

roller rockers were troublesome, it seems. They were aluminum. If memory serves they were pulled from service due to fatigue failures. He offered some to me and I was tempted, but did not pull the trigger. Found out later that there were issues.... Mel, you may remember more about this.
 
It was my understanding from the automotive world that side loading was a product of poor geometry, not the interface method (i.e. proper geometry fixes side load regardless or roller or std interface). When I set up custom engines, I would use adjustable push rods to set the proper geometry of the valve train, then make pushrods based upon that desired length. Unfortunately this can only be done with adjustable rockers, which the Lycomings don't have.

You might be able to adjust geometry by swapping different rockers/pushrod combinations to get a desired outcome. I would expect that tolerances on rocker machining in the Lcoming's to be loose, but don't know that. I have never done geometry settings on standard rockers, so not sure on the correct measurement approach. It was easily done with sharpie marker with roller rockers.

Larry

Maybe more of the automotive issues were extra poor geometry, but there is no way around it, the valve moves linearly and the rocker tip moves in an arc about the pivot axis. They will slide and put a side force on the valve.
 
roller rockers were troublesome, it seems. They were aluminum. If memory serves they were pulled from service due to fatigue failures. He offered some to me and I was tempted, but did not pull the trigger. Found out later that there were issues.... Mel, you may remember more about this.

Mine are still running without problems.
 
valve side loading

Maybe more of the automotive issues were extra poor geometry, but there is no way around it, the valve moves linearly and the rocker tip moves in an arc about the pivot axis. They will slide and put a side force on the valve.

That isn't 100% true, within a certain range of rocker angles. If the rocker geometry is set up such that the rocker to valve angle doesn't exceed 90 degrees, then the rocker tip radius can be designed to strictly "roll" on the lash cap, rather than side load it.

Skylor
 
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