Lycoming lifters

[Bob_Belville]

As posted elsewhere my IO360A1A is torn down for a prop strike. There is pitting on the cam shaft so it is being replaced with new. The shop recommends using Superior lifters of conventional design rather than new style hyperbolic lifters now being shipped by Lycoming. The concern is that the new curved lifters are reported to lower oil pressure. Apparently the new lifters have been in the market only a year?

 

Comments?

 

Bob

[N601RX]

I used Superior parts last year when I overhauled my engine.  The lifters have to be purchased as three separate parts, the lifter body, hydraulic internals, and finally the pushrod cup.   I also did the Centra-lub cam mod.  So for no problems.

[KSMooniac]

I haven't heard of the new Lycoming design and would love to hear more about it.  You might call Lycoming and ask a tech rep about the change and what the advantages are supposed to be.

 

I'll be facing a similar decision shortly when I start my overhaul.

[mike_elliott]

I used Superior parts last year when I overhauled my engine.  The lifters have to be purchased as three separate parts, the lifter body, hydraulic internals, and finally the pushrod cup.   I also did the Centra-lub cam mod.  So for no problems.

 

who did the centrilube, was it Firewall forward or Centri lube themselves?

[KSMooniac]

Centrilube will do it themselves now.  I already emailed them to check and will debate that mod vs. Ney Nozzles at some point in my  process.  I think avoiding the FF middleman is a better choice.

[N601RX]

who did the centrilube, was it Firewall forward or Centri lube themselves?

I've posted the details before, but originally sent it to FF. That turned into a 3 month nightmare. Through a 3rd party I finally learned that FF did not own the STC and located the owner of the STC. Once dealing with him directly I had the cam back in a few days. I have been flying it almost a year with no problems

[Bob_Belville]

For you voyeurs... here's what the cam looks like. 

[Bob_Belville]

I've posted the details before, but originally sent it to FF. That turned into a 3 month nightmare. Through a 3rd party I finally learned that FF did not own the STC and located the owner of the STC. Once dealing with him directly I had the cam back in a few days. I have been flying it almost a year with no problems

I left a message on the answering service in Fort Collins(?) Colorado Monday. I don't think they've called back but my repair shop talked to them, we wouild have to send them a new cam which they would drill and return for $650(?) plus shipping. The engine shop was clearly in favor of going with the stock setup from Superior. 

[jetdriven]

I would go with the newest design of lifters from lycoming.  Roller lifters would be the best but the cost is rather outrageous.  There has been a recent torrent of cam/lifter failures with Lycomings. I know 6 or 8 people on this board who have had to change engines, and a lot of it was lifters and camshafts.

[Bob_Belville]

I would go with the newest design of lifters from lycoming.  Roller lifters would be the best but the cost is rather outrageous.  There has been a recent torrent of cam/lifter failures with Lycomings. I know 6 or 8 people on this board who have had to change engines, and a lot of it was lifters and camshafts.

Thanks Byron, appreciate your advice. My engine shop strongly recommended not using the hyperbolic lifters. Says he has heard complaints of reduced oil pressure an would not be surprised if an AD is issued. 

[Bob_Belville]

I found out this morning that now Tim is not satisfied with the lifter clearance, it's too great, so he is going to bore and bush, my terms, to insure higher oil pressure. (Info 2nd hand at this point, Tim will call me later today.) He'll do that in house but I guess that means another week delay...

 

Routine? Comments?

[KSMooniac]

I'm not sure that is a good idea, actually.  Read all of the articles here:  http://egaa.home.mindspring.com/valves.html and discuss with your engine builder.  If you get the lifters too tight, it apparently will reduce the already weak flow of oil to the valves via the lifters and pushrods.  That could lead to early valve distress...

[Bob_Belville]

Scott, I looked through the docs on the site (now defunct?) and did not see anything specific to the angle valve IO360A1A. Seems to be an expose' of Lycoming design flaws. Who are these guys?

 

I have not talked to the engine builder yet but the impression I got via the A&P/IA who has my plane is that Tim just need to return the tappet/lifter clearance to new specs.

[KSMooniac]

They are some engine builders with a lot of Lycoming experience, particularly with Grumman installations IIRC.  They've been collecting their own data for many years on premature failures with Lycomings (cams and valves, primarily) and were able to correlate reduced oil flow to the valves to premature valve wear or other distress.  Their advice now is to maximize the clearance within specs of the lifters and case if I understand it correctly.  Also they recommend trying to match lifters with the most flow to the exhaust valves.

[DaV8or]

I too would like to know more about this "hyperbolic" lifter that Lycoming is doing now. I also don't know anything about this Centrilube system. I'm assuming it is small hole bored down the center of the camshaft with holes bored perpendicular in each lobe to force oil onto the lifter? Just a guess, I really don't know about it.

[N601RX]

Lycoming cams are already hollow, so they just plug up the end with an expansion plug.  They also they drill holes from the each cam bearing  surface of the cam into the center hollow part of the cam.  This allows the inside of the cam to be filled with pressurized oil.  Then they drill 2 holes in each cam lob so the oil can spray out onto the lifter face as the cam is getting ready to push the lifter up.  I had them modify my cam last year when we overhauled our engine.

[KSMooniac]

http://www.centri-lube.com/

[carusoam]

15 seconds vs 4 minutes, from start up to oil lubricated surfaces...

According to the web site.

What's the down side?

Best regards,

-a-

[kmyfm20s]

Lycoming cams are already hollow, so they just plug up the end with an expansion plug.  They also they drill holes from the each cam bearing  surface of the cam into the center hollow part of the cam.  This allows the inside of the cam to be filled with pressurized oil.  Then they drill 2 holes in each cam lob so the oil can spray out onto the lifter face as the cam is getting ready to push the lifter up.  I had them modify my cam last year when we overhauled our engine.

I can't see a hole that is drilled through a Cam lobe to add pressurized oil being beneficial. Our concerns with the Lycoming engine is the initial engine start ups and periods of non operation. If anything it exposes the more susceptible areas of the Cam to be attacked by corrosion and decreases the amount of hardened surface area to interface with the tappet. The hole could actually be an areas where the oil is scrapped off the tappet until the oil pressure kicks in after several revolutions. It also has to alter the oil pressure in the galleys which effects the hydraulic lifters and bearing which do require the oil pressure to operate. This is just speculation on my part but seems reasonable to me.

[mike_elliott]

I can't see a hole that is drilled through a Cam lobe to add pressurized oil being beneficial. Our concerns with the Lycoming engine is the initial engine start ups and periods of non operation. If anything it exposes the more susceptible areas of the Cam to be attacked by corrosion and decreases the amount of hardened surface area to interface with the tappet. The hole could actually be an areas where the oil is scrapped off the tappet until the oil pressure kicks in after several revolutions. It also has to alter the oil pressure in the galleys which effects the hydraulic lifters and bearing which do require the oil pressure to operate. This is just speculation on my part but seems reasonable to me.

 

 

Oil holes in cams are typically drilled on the back side of the lobe, where the cam will not be exerting force on the lifter. With oil flowing onto the surface of the cam vs. being shot at by an angry crank every now and then will cover the lobe more effectively with oil. Oil pressure should be compensated for by adjustment in any event. Corrosion will be mitigated some, but not much I believe. The  real value is reduced cold dry start time and reduced cam/lifter temps and friction. Once corrosion sets in, you will eventually spall, but this event happens faster if you run the surfaces dry for longer periods of time. Bottom line, I believe it is a good idea. Does it fix the design deficiencies of the Lyc? Not completely. I cannot see where it would hurt, however, and will be part of my next IO360 rebuild if GA is still alive when I need it.

[Shadrach]

15 seconds vs 4 minutes, from start up to oil lubricated surfaces...

According to the web site.

What's the down side?

Best regards,

-a-

4 minutes... Really? I have never heard that. If true, that means there are lubricated components in the engine that have gone without lubrication for several hours on there way to TBO.

[DaV8or]

I cannot see where it would hurt, however, and will be part of my next IO360 rebuild if GA is still alive when I need it.

 

Unless those holes cause camshaft failure. I wonder if they have had any? I once owned a '64 Ford Falcon and I rebuilt the engine and when I did, I put in a brand new camshaft. I can't remember what brand right now, but about three years later, it snapped in half. Bad metallurgy I guess, but camshaft failures do happen and I wonder if drilling holes could weaken the shaft, or inadvertently cause stress risers?

[DaV8or]

4 minutes... Really? I have never heard that. If true, that means there are lubricated components in the engine that have gone without lubrication for several hours on there way to TBO.

 

I kind of take that websites claims with a grain of salt. Their claim is, the reason we have so many camshaft spawling problems is because we switched to 100LL. I kinda think that's BS.

[cliffy]

Frequent flying does more to enable your engine to make TBO than anything else. If you're not doing 50 hrs a year (as a bare min) or more you're not flying enough even to stay current let alone keep you engine in good shape.