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Sticking valves?

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ultimate10201

Member
I have what appears to be sticking exhaust valves on my freshly overhauled IO 360 A1B engine mounted in my RV7. This is an older engine that doesn’t have the counterweighted crankshaft.

Currently I have about 84 hours on the engine SMOH. The cylinders are reconditioned, steel nitride, .010 over, and were provided with new valves, seats, springs, pistons, pins, and rings. Break-in seemed normal and CHTs never got anywhere near out of hand – the highest I saw was #3 @ 375° which dropped down quickly within the first hour. My baffling and cooling works very well. I’ve never seen CHT‘s go over 360° in an aggressive climb on a hot day here in Texas and normal cruise will show a CHT spread from 320° to 345°.

I first noted the problem around 60 hours on my #3 cylinder. Currently, at start up, everything seems normal, EGT‘s climb as expected but after about 40 to 50 seconds, number three cylinder begins to drop out rapidly, #3 EGT drops from ~ 900° to < 300°, and the engine runs very rough. Very rough. I’m reluctant to let it keep running until it smooths out because it is so rough - literally shakes-the-airplane rough - but if I leave it alone, in about a minute, it smooths out and then I have a regularly operating engine with good throttle, mixture, and prop response for as long as I care to fly.

Surely does sound like a sticking valve that “heals” once it gets warm.

To add to the mystery, during the last 3 or 4 startups, #4 cylinder is beginning to misbehave similarly as well.

I’ve done all the ‘easier’ diagnostic things: tested the mags, the leads, the plugs, and I ran a fuel flow test which showed very even distribution. I removed the #3 rocker box cover, the rocker, the pushrods, the shroud, and I pulled out the hydraulic plunger assemblies just to be sure I didn’t have some kind of blockage or leak down anomaly.

I didn’t find anything obvious; and it still happens that everything works fine once the cylinder warms up; at that point, magically, the symptoms are just gone.

I’d appreciate any input before I go ahead and start trying the rope trick or possibly just pulling those two cylinders and taking them to the cylinder shop.
 
As the problem migrates between #3 and #4 cylinder, and you just did major engine work, I’d look toward a common source.

If you have a chunk of junk floating around in the spider it can migrate around affecting one cylinder than another. The problem goes away at power as the spider diagram moves down to expose more fuel port. We saw your same problem on an RV8A after the injection system went in for inspection. We too assumed it was a stuck valve. We knew it was not when the problem moved. We opened and cleaned out the spider - problem gone.

Carl
 
Carl Froehlich said:
As the problem migrates between #3 and #4 cylinder, and you just did major engine work, I’d look toward a common source.

If you have a chunk of junk floating around in the spider it can migrate around affecting one cylinder than another. The problem goes away at power as the spider diagram moves down to expose more fuel port. We saw your same problem on an RV8A after the injection system went in for inspection. We too assumed it was a stuck valve. We knew it was not when the problem moved. We opened and cleaned out the spider - problem gone.

Carl
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Carl.
Does the spider di·a·phragm really move down to expose more of the fuel ports?
 

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find a Robinson heli mechanic to do the wobble inspection. they do them all the time because of the SB on the Robinson helicopters. takes about an hour to do the work.
 
Full Throttle said:
Carl.
Does the spider di·a·phragm really move down to expose more of the fuel ports?
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A quick search yielded the attached description. Note that as the spider diaphragm moves, the fuel “V” for each cylinder is more exposed. The small opening at the apex of the V provides for a leaner minute and smooth idle.
https://precisionairmotive.com/wp-content/uploads/2019/06/15-812_b.pdf

To verify what is going on, I suggest the “shot glass” test. This is what demonstrated our issue with a chunk of crud in the spider. Here is our test result:

Carl
 

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Thanks for the responses and I apologize for being so long in getting back.

I think I left the impression that either #3 or #4 was dropping out on me - migrating - but actually for a brief time, both #3 and #4 were dropping out at the same time. #4 has been truly unpredictable but #3 continued to show these symptoms when I started working on the problem.

I did all the obvious stuff :

Checked the mags, mag timing, ignition leads, tested (spark and resistance) and cleaned the plugs.

Made sure I didn’t have induction leaks.

I removed and cleaned the injector nozzles and then did the flow divider test. I’ve included a picture of the results I got; I’m not sure how I could get the flow any more even than the picture shows. A knowledgeable friend removed the cap from the flow divider, and declared the diaphragm was in excellent shape. He suggested I remove the 90° fitting for the fuel supply from the injector body up to the flow divider because sometimes they would get rusty and maybe have some rust particles break off and get into the spider. I did that but it turns out the fitting is stainless steel so somebody had anticipated that problem years ago. What I could inspect of the inside of the flow divider body looked bright, shiny, clean.

I removed the rocker arms, the pushrods, and the pushrods shrouds, then pulled out the hydraulic plunger assemblies and cleaned them. Nothing appeared wrong, no blockage, or other obvious problems, and the springs and ball inside the assembly behaved as advertised when tested. I reassembled the valve train components and assured the required dry tappet clearance of less than .080 and more than .028.

I also contacted our local cylinder shop guru. He’s been in the business for a long, long time here in North Texas. I told him the problem, the time on the cylinders (60 hours when it first happened), etc., Then he asked me if I was using Camguard. I told him yes and he suggested I drain the oil to get the Camguard out of the system, then add oil back in with no additives and further to add MMO in the sump. I’m not sure, but maybe he was suggesting that the Camguard was too sticky, perhaps on such lowtime cylinders, and that’s what was making for sticky valves guides.

What I had done, at 50 hours, was I had determined the cylinders were broke-in: CHT temps were good, oil usage was 7 to 8 hours per quart and I thought I was in tall cotton. So I stopped using pure mineral oil, went to Shell 100 and added Camguard per the instructions. 10 hours later, the problem began.

After changing the oil and adding the MMO, I have run the engine twice and flown it for about an hour. When I ran it yesterday, it was pretty warm day here in North Texas and I did not get the morning sickness symptoms that I had been experiencing nor did I get them last time I ran the engine up. At this point, I’m going to make sure that I get good mag checks at run up and fly the plane as long as the engine is running smoothly.

I’m skeptical about the MMO treatment, but it does not alter the fact that my engine has several episodes of smooth running, and all cylinders run normally with continually climbing EGT readings whenever I do I start up now. Perhaps it’s a combination of warmer weather which does not allow the valve guide to become cold-soaked overnight, the MMO treatment, the removal of the Camguard, and even possibly some of the other things I did that fixed a problem I didn’t realize was corrected when I was cleaning and inspecting.





IMG_4208.jpeg
 
My guess is he recommended the MMO to clean out any leftover Camguard as MMO contains a solvent element in its chemistry.
Hope things stay good.
 
ultimate10201 said:
I also contacted our local cylinder shop guru. He’s been in the business for a long, long time here in North Texas. I told him the problem, the time on the cylinders (60 hours when it first happened), etc., Then he asked me if I was using Camguard. I told him yes and he suggested I drain the oil to get the Camguard out of the system, then add oil back in with no additives and further to add MMO in the sump. I’m not sure, but maybe he was suggesting that the Camguard was too sticky, perhaps on such lowtime cylinders, and that’s what was making for sticky valves guides.

What I had done, at 50 hours, was I had determined the cylinders were broke-in: CHT temps were good, oil usage was 7 to 8 hours per quart and I thought I was in tall cotton. So I stopped using pure mineral oil, went to Shell 100 and added Camguard per the instructions. 10 hours later, the problem began.

After changing the oil and adding the MMO, I have run the engine twice and flown it for about an hour. When I ran it yesterday, it was pretty warm day here in North Texas and I did not get the morning sickness symptoms that I had been experiencing nor did I get them last time I ran the engine up. At this point, I’m going to make sure that I get good mag checks at run up and fly the plane as long as the engine is running smoothly.

I’m skeptical about the MMO treatment, but it does not alter the fact that my engine has several episodes of smooth running, and all cylinders run normally with continually climbing EGT readings whenever I do I start up now. Perhaps it’s a combination of warmer weather which does not allow the valve guide to become cold-soaked overnight, the MMO treatment, the removal of the Camguard, and even possibly some of the other things I did that fixed a problem I didn’t realize was corrected when I was cleaning and inspecting.
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First I've heard of anything negative about CamGuard.
 
Camguard is NOT the problem. That sounds like the birth of a new OWT. (Old wives tale).

It is quite likely the work you have done has corrected an issue and you do not realise it.
 
Daryle, Is it possible the valves were a bit tight in their guides and just loosened up with more time on the engine? I can't see in your posts if you did the wobble test that Ed recommended.
 
rv8ch said:
Daryle, Is it possible the valves were a bit tight in their guides and just loosened up with more time on the engine? I can't see in your posts if you did the wobble test that Ed recommended.
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I have not done the wobble test simply because getting the fixtures and tools, or somebody with those resources, has been problematic. It is my next step if the problem persists.

You may have made a good guess here. A local mechanic at my airport (an IA) said much the same thing: that maybe the valve guide was tight, possibly under-reamed, and that I didn’t allow the engine to quite break in before shifting to standard detergent oil.

I did what the cylinder shop owner suggested – drain the oil, replace it with only mineral oil and MMO - and I have subsequently put a little over four hours on it, including 3.7 or 3.8 hours of flight time which has been glitchless. The symptoms lessened quickly after the oil change, then went away. Again, it may be a combination of factors: tight guides not quite broken-in, less viscosity and more solvent action in the oil with the addition of the MMO, warmer OAT here in North Texas, and the outside chance that some of the procedures I did may have fixed something about which I was unaware.

thanks to everyone for your input.
 
Good to hear that it's getting better! One point - I believe that experts like Mike Busch have said that using detergent oil for engine break-in is ok - the thing to avoid is anything that claims to reduce wear, or anti-scuff.
 
I don’t recommend any additives until at least 100 hours. I also run Phillips X/C 20W50 and put MMO in the fuel. Phillips oil is an approved break in oil and I find it does a really good job of keeping the compressions good. My RV-10 with 1100+ hours on it has compressions of 80/80 on 3 cylinders and high 70’s on the others. The Jacobs radial in my Stearman with 445 hours, which I also broke in new and have treated the same way, was checked yesterday and has compressions of 80/80 on 5 cylinders and 76 & 79 on the other 2. All compressions were done cold. The 10 burns 2-3 qts of oil in 35 hours and the Stearman burns about 3 qts in 25 hours.

Vic
 
I use MMO religiously, but on a new or overhauled engine I also like to wait until 100 hours before I add the Marvel. Break in w/Phillips 20W50XC, then switch to Victory.
 
My neighbor's C182 had the morning sickness, somewhat like what is described here. The engine idled very rough but smooth out when power was applied. It turned out that it was an intake leak. He used a borescope to get around the obstacles to find the leak as it was not apparent by "naked eye". Perhaps you have the same issue.
 
Are those that are using MMO using it at the label rates? Are you using in both the fuel and oil?
 
Just another anecdotal observation about using MMO; around 10 years ago I had a stuck valve and had a local mechanic pull the jug and work his magic to fix it. After it was all buttoned up and “Ops check okay”, he recommended using MMO in the fuel. I’ve been pretty diligent about using the mix on the label, 8 oz added to one 21 gal tank to when refueling. No sticky valves or morning sickness since… 🤞
 
Jetmart said:
Are those that are using MMO using it at the label rates? Are you using in both the fuel and oil?
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I found that using MMO in the oil thinned it out enough that the oil temperatures increased. 2 oz/5 gallons of fuel or 6 oz in a 16 gallon tank, which is what the bottle recommends. Does it do anything? That is a popcorn evening subject that has been fiercely debated for years! 🍿
 
vic syracuse said:
I don’t recommend any additives until at least 100 hours. I also run Phillips X/C 20W50 and put MMO in the fuel. Phillips oil is an approved break in oil and I find it does a really good job of keeping the compressions good. My RV-10 with 1100+ hours on it has compressions of 80/80 on 3 cylinders and high 70’s on the others. The Jacobs radial in my Stearman with 445 hours, which I also broke in new and have treated the same way, was checked yesterday and has compressions of 80/80 on 5 cylinders and 76 & 79 on the other 2. All compressions were done cold. The 10 burns 2-3 qts of oil in 35 hours and the Stearman burns about 3 qts in 25 hours.

Vic
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What is the correct ratio of MMO to fuel?
 
Thanks, Moe, for the offer! I have a friend that is a mere 2 hangar rows away from my hangar row who has an angle valve wobble test tool. I didn’t know until he happened to stop by. I’m going to continue on the current path, having restored break-in oil procedures as per my last post, before borrowing his tool.

By the way, I have actually been to Cherry Hill, New Jersey. It was 1981, I was a young man working for the Bonanza restaurants chain if you can remember them. I went to a local franchisee there to do a sales audit and then went out to the New Jersey countryside to a place called Hattieville I believe For another audit. What many Texans don’t know is that New Jersey has a beautiful countryside West of the coastal congestion.
 
Again, thanks to all for the responses! I am continuing with the procedure where I’ve more or less re-started the break-in process - using mineral oil but modified by the addition of the MMO. The instructions on the MMO container said replace 20% of the oil going into the sump. When I drained and changed the oil (containing the Camguard), I added 6 quarts of mineral oil and 1/2 quart of MMO. I also added MMO to the fuel per the instructions on the container.
 
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