Hi Guys and Gals,
My partner and I have been researching Lycoming engines before we order one for our RV-8. We stumbled across this series of articles that I thought the membership here would find interesting. We are planning a 180 horse O-360 for our RV and this main article, called "The Rest of the Story" is very pertinent to this engine.
To find these informative articles, go to http://precisionengine.home.mindspring.com/engine3.htm
If you find yourself too busy to bother with this, in a nutshell, this article chronicles the development of the Lycoming valve lifters, and the subsequent problems with the hydraulic lifter design that precludes adequate oil feed to the valve guides and rockerboxes. The result of this self created problem, is the premature failure of the exhaust valves and guides on the right bank cylinder heads of the Lycoming O-320, O-360, and O-540 engines. In the last few years, Lycoming has come out with a modification for the O-540 series that fixes the problem, and is not cheap!
Happy reading.
Pete
Oil Feed Issues on Lycoming Engines
Oil Feed Issues on Lycoming Engines
Peter Marshall
Newbie RV-8 builder.
You wanna draw, ....against the fastest rivet gun in the West??? LOL
Newbie RV-8 builder.
You wanna draw, ....against the fastest rivet gun in the West??? LOL
That would have to be one of the most interesting reads that I have had in a long time.
Everyone, take the time to read, slowly so you understand, as it does make alot of sense.
Makes you want to run a few extra oil lines.
Everyone, take the time to read, slowly so you understand, as it does make alot of sense.
Makes you want to run a few extra oil lines.
RV-7A Emp
I would rather have a bottle in front of me than a frontal lobotomy.
I would rather have a bottle in front of me than a frontal lobotomy.
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Guest
Yes,
I received a letter from Bill Scott of Precision Engines. He told me how they work around this problem by calibrating the lifters for different cylinders on the engine. The "leakiest" lifters are placed in the areas with the lowest local oil pressure. They also "open up" the clearances on the lifters so that there is more leakage around the perifery of each lifter and thus more oil flowing into the rockerboxes and leakage onto the exhaust valve guides.
Sounds good to me
Cheers, Pete
I received a letter from Bill Scott of Precision Engines. He told me how they work around this problem by calibrating the lifters for different cylinders on the engine. The "leakiest" lifters are placed in the areas with the lowest local oil pressure. They also "open up" the clearances on the lifters so that there is more leakage around the perifery of each lifter and thus more oil flowing into the rockerboxes and leakage onto the exhaust valve guides.
Sounds good to me
Cheers, Pete
Peter Marshall
Newbie RV-8 builder.
You wanna draw, ....against the fastest rivet gun in the West??? LOL
Newbie RV-8 builder.
You wanna draw, ....against the fastest rivet gun in the West??? LOL
-
Guest
Pete,
Not sure about the article, but the hydraulic lifters originated in a late 1930's Cadillac. The major problems with these lifters is that bleed down clearances are rarely checked or set properly, the result of which will lead to valve train related failures. It's an unbelievebly simple process, but understood by few and rarely checked by many mechanics.
Set correctly lifter and/or related problems are rare.
What Lycoming valve train can use are roller rockers to prevent valve guide wear, roller cam to reduce wear and improve performance, and since Lycoming is the only flat engine that positioned the camshaft above the crank. lubrication is of concern. A beehive type valve spring would control vibration better than dual springs, and lighten the valve train.
There is a cam with oil holes drilled in the lobes, which the maker refuses to sell unless purchased with one of their rebuilt unit. This would be a simple and very effective method of guarding camshafts.
Superior is supposed to be working on a roller/hydrulic cam.
There was one on the market a few years ago, but the maker, Ken Hatfield passed away. It was "absorbed" by an outfit in Arkansas, and they disappeared, and the latest is Superior. I think it's a reincarnation of Ken Hatfields work.
Not sure about the article, but the hydraulic lifters originated in a late 1930's Cadillac. The major problems with these lifters is that bleed down clearances are rarely checked or set properly, the result of which will lead to valve train related failures. It's an unbelievebly simple process, but understood by few and rarely checked by many mechanics.
Set correctly lifter and/or related problems are rare.
What Lycoming valve train can use are roller rockers to prevent valve guide wear, roller cam to reduce wear and improve performance, and since Lycoming is the only flat engine that positioned the camshaft above the crank. lubrication is of concern. A beehive type valve spring would control vibration better than dual springs, and lighten the valve train.
There is a cam with oil holes drilled in the lobes, which the maker refuses to sell unless purchased with one of their rebuilt unit. This would be a simple and very effective method of guarding camshafts.
Superior is supposed to be working on a roller/hydrulic cam.
There was one on the market a few years ago, but the maker, Ken Hatfield passed away. It was "absorbed" by an outfit in Arkansas, and they disappeared, and the latest is Superior. I think it's a reincarnation of Ken Hatfields work.
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Altoq
Exh Valves and Guides
This artical has been around for a while and I have read it over and over through the years. I keep looking for something I missed. I never could convince myself that lack of lubrication was the main cause of the problem. There are some errors in the artical.
I'm not saying that anyone should disreguard this information, but if you can't look in the mirror an say, "I completely understand the functions of a hydraulic valve lash adjuster." turn off the bench grinder and find a profesional who can.
Time would be better spent inspecting the cylinder head cooling fins between the intake and exhaust ports and and removing what ever casting flash you find there. Many have done this with good results. I will say that if you haven't already done this, you're going to be surprised.
I'm not saying that anyone should disreguard this information, but if you can't look in the mirror an say, "I completely understand the functions of a hydraulic valve lash adjuster." turn off the bench grinder and find a profesional who can.
Time would be better spent inspecting the cylinder head cooling fins between the intake and exhaust ports and and removing what ever casting flash you find there. Many have done this with good results. I will say that if you haven't already done this, you're going to be surprised.