Lycoming 0235 C1 valve lifter specs

larryjmillermd · Post by **larryjmillermd** » Sat Mar 18, 2006 23:28

My engine is a Lycoming 0235 C1 (115 hp), 500 hours SMOH. I have noted a gradual decrease in my power and rpm during takeoff. I have tired everything suggested in this forum, including new mags, new carburetor, new plugs, new throttle cable, adjusted the tappets, new air intake and air filter, proper leaning, checked the tachometer, and checked the compression (perfect).

Technicians at Lycoming said that my problem might be that the camshaft lobes are flattening out. If this is the case it could explain the low power because the valves are not opening sufficiently. Here is the catch. They refuse to tell me (or they don’t know) what the normal throw of the valve lifters should be. They just said to measure all 8 and if they are about the same there is no problem. I kept asking them for a number but they insisted that I didn’t need to know.

So I measured the throw of the lifters and found them all to be nearly identical. How does this prove that not all of the camshaft lobes are flattening out simultaneously? That seems more likely to me than just one failing.

Do any of you ace mechanics know what throw measurement I should expect? Or the next time you are adjusting the tappets on a 0235 could you also measure the throw of the lifters and let me know?

Thanks for your help.

Larry

Post by **joea** » Sun Mar 19, 2006 02:18

Larry,

The guys at Lycoming are FOS (full of brown material) if they say that they cannot tell you what the lift is. Any good shop with a cam machine can tell you what the lift is on any cam.

I believe that you have already answered your question. If you have been doing oil samples every few oil changes and not found any large amount of metal in the oil, and the lift is approx the same for all your lifters, then your cam lobes are not wearing down. One or two lobes might wear down but doubt that all would wear down the same amount.

I would look elsewhere... and might buy an Aeronca with a Continental engine in it next time.

Joe A

Don Eide · Post by **Don Eide** » Sun Mar 19, 2006 07:52

Joe,

Are you thinking 65 Lycoming?
If so, I agree with your statement.
Larry said he has an 0-235 115hp Lycoming.
That engine is used in many different airplanes
and for the most part has been a good engine.
I have one in my Champ and just love it.

Larry, Have you checked the exhaust system?
If it's partially plugged, you will get reduced power.
If it's totally plugged your engine will not run.

Hope this helps,

Post by **joea** » Sun Mar 19, 2006 09:29

Don,

No, was saying that regarding anyone who would help out a engine owner by giving him a ballpark spec on the valve lift. This is not rocket science and all they had to do is to say that the lift should be at least "230 thou, to 250 thou" then you are good.

He is trying to troubleshoot a problem, not steal tech secrets from them. The lift from the cam on his engine is something that they probably publish anyway, I just do not know where to find it.

Joe

nowlen · Post by **nowlen** » Sun Mar 19, 2006 10:05

does the 0-235 had hydraulic lifters ? if so that could be the problem. the lift # is somewhere, perhaps in the o/h manual. lycoming used different pushrod lenghts to get the valves to open the right amount even with hydraulic lifters.

k mielke · Post by **k mielke** » Sun Mar 19, 2006 11:04

push rod length has nothing to do with the distance traveled by the valve a specific lash has to be maintained . cam is the only thing that can change the distance traveled by the valve, also if the compression is good than the valves are probably opening and sealing just fine[must be checked with compression style gauge]air in air out

larryjmillermd · Post by **larryjmillermd** » Sun Mar 19, 2006 11:32

Joe,

I agree that Lycoming technicians demonstrated less than optimal customer service when I called them. But overall I like the engine.

Don,

I have a “new” exhaust system without a muffler. It is wide open. If you want to hear the engine log onto my website under re-certification. The engine sort of sounds like a Harley. I hope the neighbors don’t mind:

http://homepage.mac.com/larrymmd/iMovieTheater11.html

Nowlen,

Lycoming 0235 is one of their old engines that does not have hydraulic valve lifters. That is why you have to adjust the tappets frequently (every hundred hours). The lifters can be aluminum or steel. Mine are steel. I have not checked the oil for metal parts. I will do that.

Thanks for the advice. Much appreciated,

Larry

MikeB · Post by **MikeB** » Sun Mar 19, 2006 14:44

Larry,
You probably posted the conditions you were experiencing once before (rpm, etc.) but could you post them again? I know Don has a similiar A/C (Champ with 235) so you should be able to compare notes with him regarding prop, rpm, etc. It does seem that you've tried all the obvious trying to solve the problem. I can only think of a couple others: i.e. restricted fuel line or tank vent problem. Are you sure the mag timing is exact on? If the engine idles smoothly, I doubt the cam lobes are flattening, but if they were (as others have said) there should be excessive metal in the oil filter. Intake leaks comes to mind, but guessing they've been checked, also.

A exhaust temperature gauge would have been helpful if you had a known (good) condition to check it against.

Mike

larryjmillermd · Post by **larryjmillermd** » Sun Mar 19, 2006 16:22

Mike,

Go to the Engine and power plant section in this forum. My original post on Sept 8th was entitled “Poor power with Lycoming 0235”. I got many great suggestions that I have tried.

The bottom line is that I can only get 2300 rpm on climb out and 2550 rpm in straight and level flight.

I am beginning to believe I have a miss-match between the engine and the prop that was recommended by Sensenish (76AM2-44). If my engine cannot turn the proper rpm, it cannot achieve its maximum horsepower, regardless of what that maximum might be.

I also believe I am a victim of my own unrealistic expectations. With over 1,200 hours in a Turbo 210, I may have forgotten what it is like to fly in a slow and low trainer like the Champ that I originally learned to fly in. Don’t misunderstand me, I am having a ball. The Champ is a whole lot more fun to fly (who wants to climb out at 1,500 feet per minute, set the auto-pilot at 26,000 feet at an indicated air speed of 220 mph and just sit there for the next 4 hours until you reach your destination?) With the Champ you have to fly the plane every second and you get the real feel of flying, using the rudder in coordinated turns etc.

The other day I was flying into a head wind of 35 knots at 4,000 and slowed the Champ to just above stall. My ground speed (Garmin GPS) was 13 mph. My goal is to slow the plane to Zero mph and call approach, “San Antonio approach, Champion 9858Y is with you at 4,000 feet.” “58Y squawk 0435 and ident”. ----- “58Y what is your indicated airspeed? We show you sanding still”. That would be so cool.

I am now getting used to a climb rate of 300 feet per minute, a top speed of 100 mph, and a service ceiling of 7,000 feet, so all this grief over poor performance may just go away. Hell, my Champ is way faster than a balloon.

Thanks so much for your input.

Larry

nowlen · Post by **nowlen** » Sun Mar 19, 2006 23:30

k mielke wrote:push rod length has nothing to do with the distance traveled by the valve a specific lash has to be maintained . cam is the only thing that can change the distance traveled by the valve, also if the compression is good than the valves are probably opening and sealing just fine[must be checked with compression style gauge]air in air out

maybe you don't understand basic mechanics. if the pushrods are longer the valves open sooner, close later and open more. suggest you go back to school

larryjmillermd · Post by **larryjmillermd** » Sun Apr 02, 2006 22:30

I don’t want to start World War III here but k. Mielde is right. Adjusting the tappets compensates for any discrepancy in the lengths of the push rods. Only the cam lifters affect the distance the valves open.

Post by **joea** » Mon Apr 03, 2006 00:14

Did you ever find out what kind of lift you should be seeing at the rocker arm?

larryjmillermd · Post by **larryjmillermd** » Mon Apr 03, 2006 03:16

I could never find any specs on the desired lift. Just that they are all nearly the same and no metal in the screen.

Dennis · Post by **Dennis** » Mon Apr 03, 2006 08:49

It really irritates me that Lycoming will not make know the specs on a cam. It just occured to me that if someone has a cam laying around, preferably a new or regrind, why not mike the two diameters on one lobe and take the difference. The difference should be the lift. Might do it on several lobs and average them. The "calculated" lift should be the same, or close, at the push rod.

Dennis