The International Cessna 170 Association

Hello all,

Looking for advice regarding my engine. I had a exhaust valve stick open on my number 1 cylinder. The mechanic removed the cylinder and discovered a cam lifter that was not rotating and damaged. Anyway he said the case has to be split and the motor would have to be sent out. He has a "guy" in Virginia. Not sure who that is, can anyone suggest a shop that they would recommend? Thank you very much. This kind of hit me out of left field....ugh

Pete

True the case has to be split. Lots of work. Because it is so much work many consider an overhaul at this time. That of course is even more money but not necessarily much more work.

In suggesting the engine has to be sent out your A&P has told you he doesn't have the expertise to do the work or he doesn't want to get involved. Your better of he is straight with you. But it does not take a special shop, just someone with an A&P who wants to get involved. I'd be looking for someone who has spit the case on a small Continental before.

Where are you located? Helps people to know who to suggest.

Bruce Fenstermacher wrote:...In suggesting the engine has to be sent out your A&P has told you he doesn't have the expertise to do the work or.....

Being the suspicious sort that I am.... I've never heard of a cam lifter not rotating and causing a stuck valve. I guess it could happen. I've just never heard of that sticking a valve. More likely that would increase cam-lobe wear.

What I HAVE heard of, however.... is an unknowledgable mechanic ..... rather than using the "rope trick" to unstick a valve... foolishly pulling a cylinder..... and, ...since he didn't know what he was doing... yanked the push-rod out of the valve lifter body... which was the older type. This creates a suction in the socket of the lifter ...pulling it and it "cocks" the lifter out of position, and when the engine is then rotated...(by hand via the prop)... the lifter is CRACKED and broken. NOW the engine has to be split.

I suppose the owner must then be told the lifter was damaged.

Hi I am on Long Island and the plane is up at 44n. We were on our way back from Oshkosh and got stuck there. I saw the stuck valve, it was completely frozen open. I have replaced 3 cylinders in the last few years, and actually shipped the guy at sky acres 3 new cylinders to replace the remaining older ones, when he discovered the other problem. The engine was overhauled in the 90's and has 700 hours on it.

Not rotating means the face of the follower is toast and likely the camshaft as well. 700 hours, with now new cylinders, tough call whether to repair and time continue or go the extra and overhaul. It would be nice to get it all past you so you can fly trouble and worry free.

To bad. A few years ago you would have just driven the engine to Mattituck out on the island.

As Jim noted, if the lifter/follower is bad, likely your cam is as well. Another reason your mech probably doesn't want to get into it. He fears more will be found.

this is going to take a lot of thought, have to decide taking the engine apart and doing just whats necessary, or going for a complete overhaul. My local guy is recommending to just do whats required now because of the cost and the value of the plane. The last overhaul indicates the crank was "standard size" he told me thats good news.

You'll know what to do once the case is split. The unknowns can be daunting (Cracked crankcase? Gear train passing inspection? etc.)

I'm wondering why a lifter would fail to rotate...unless for long inactivity rust has set up in there and frozen it....in which case you're likely looking at a major repair either way.

BTW: Just so everyone is on the same page.... theres a HUGE difference in what is termed a "Major Overhaul" and a "Major Repair". The vast majority of all the engines flying out there in these airplanes have never been "overhauled". They have been "repaired". Total time continues in such cases with the notation of XXS hours since Major Repair. (NOT SMOH) Replacing cylinders, new bearings and gaskets do not alone qualify for the definition of "overhaul". (Even tho' that's the term which has commonly slipped into the discussions.)

Is your mechanic familiar with O-300s???? I'm skeptical like GA. Much like human medicine, airplane medicine often requires a second opinion.

gahorn wrote: BTW: Just so everyone is on the same page.... theres a HUGE difference in what is termed a "Major Overhaul" and a "Major Repair". The vast majority of all the engines flying out there in these airplanes have never been "overhauled". They have been "repaired". Total time continues in such cases with the notation of XXS hours since Major Repair. (NOT SMOH) Replacing cylinders, new bearings and gaskets do not alone qualify for the definition of "overhaul". (Even tho' that's the term which has commonly slipped into the discussions.)

The word "Major" is actually a misnomer. Overhauling or repairing an engine is not a Major Repair according to FAR 43.

Correct. The common parlance uses the term because for so many years "top" and "bottom" "overhauls" were tossed around so freely (themselves unrecognized by authorities.) "Major" came to refer to the entire engine (both top and bottom.)

The point I was hoping to make is that many extensive engine repairs (intended to renew the major wear components) are called "overhauls" contrary to the meaning of the FAR.

The engine is being shipped out to aero engines in winchester VA for evaluation, will keep you posted...thanks for all the input.

gahorn wrote:

Bruce Fenstermacher wrote:...In suggesting the engine has to be sent out your A&P has told you he doesn't have the expertise to do the work or.....

Being the suspicious sort that I am.... I've never heard of a cam lifter not rotating and causing a stuck valve. I guess it could happen. I've just never heard of that sticking a valve. More likely that would increase cam-lobe wear.

What I HAVE heard of, however.... is an unknowledgable mechanic ..... rather than using the "rope trick" to unstick a valve... foolishly pulling a cylinder..... and, ...since he didn't know what he was doing... yanked the push-rod out of the valve lifter body... which was the older type. This creates a suction in the socket of the lifter ...pulling it and it "cocks" the lifter out of position, and when the engine is then rotated...(by hand via the prop)... the lifter is CRACKED and broken. NOW the engine has to be split.

I suppose the owner must then be told the lifter was damaged.

Exactly what I was thinking George...

We can all speculate but I also hear Joe Friday " Just the facts man (ma'am)" from the engine tear down report.
Maybe a pic of the face of the offending lifter, our equivalent of DNA evidence, is what I (maybe we) want.

Hi, just to clarify.... the number 1 cylinder had the valve issue. I told the mechanic to also replace number 6 because it also had the same time on it as 1. When he removed 6 he looked through and saw the lifter damaged. The lifter had nothing to do with the exhaust valve on number 1. The two issues have nothing to do with each other.