What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Valve Issue

UrbanM

Active Member
Compression Ratio

Dear list.
Had an issue come up during engine runup that is going to cause me to have to replace a cylinder. I have an experimental version of a 0-320 E2D wide deck with 9.2 C/R. Due to prior history I am considering a top overhaul on the other 3 and while I am at it I may consider changing the compression ratio back to a more stock 8.5. The engine data plate shows 9.2 so would I need to change this? Would it be considered a major change or alteration? If anyone has been through this tell me what you think.
Thanks,
Kirk
 
Last edited:
Dear list.
Had an issue come up during engine runup that is going to cause me to have to replace a cylinder. I have an experimental version of a 0-320 E2D wide deck with 9.2 C/R. Due to prior history I am considering a top overhaul on the other 3 and while I am at it I may consider changing the compression ratio back to a more stock 8.5. The engine data plate shows 9.2 so would I need to change this? Would it be considered a major change or alteration? If anyone has been through this tell me what you think.
Thanks,
Kirk

NOT an expert! But here's my thoughts. Do you hold the repairman's certificate? If so, it's my understanding you can do whatever you want. What's the valve issue? There are methods to lap valves in place and maybe save the cylinder?
 
NOT an expert! But here's my thoughts. Do you hold the repairman's certificate? If so, it's my understanding you can do whatever you want. What's the valve issue? There are methods to lap valves in place and maybe save the cylinder?

The Repairman certificate lets the holder sign off the annual condition inspection. Period. Nothing else. Anyone may legally work on an EAB aircraft. Experimental engine, data plate means nothing. The only legal question is whether or not this is a major change, requiring a return to phase 1 OpLimits. Best not to guess: ask a DAR or call your FSDO.
 
Thanks for the responses, guys! Bob, you nailed it, its the legal question. Local FSDO has not been helpful with amateur built stuff and EAA had a very knowledgeable informative staff but many of them were layed off during COVID. To top this off my local and highly regarded DAR retired recently and left a huge void.
So here is the back story; I purchased the plane from from the builder who had an experimental 320 E2D built from parts (And with a Data Plate) by a repudiable shop (Whose name I won't mention). At around a hundred hours an intake valve stuck open which bent the pushrod and resulted in a landing at the nearest airport. Cylinder assembly replaced and then at the next condition inspection low compression on another cylinder caused by the ring gaps being all lined up. That cylinder was replaced. I bought the plane about 200 hours later and figured the engine issues were behind me. Compressions were excellent, oil usage was 1 qt per 25 hours and the oil analysis and filter inspection were well within limits at every change. At 385 hours an intake valve on another cylinder broke near the top of the stem and decided to exit the engine by busting a hole in the top of the cylinder. I can post pictures but some viewers may find them disturbing.
The paperwork shows all new Lycoming valves were used and I have stacks of yellow tags for all the parts that were not new. I am at a loss to understand how a clean well built engine can have these issues. I spoke with the shop in Alamosa Co and they said they have never heard of a stuck intake valve (Plenty of exhaust valves of course). So my options are replace the cylinder assembly with the big viewing port in the top, or top all 4 cylinders to make sure I have fresh quality stuff, or lastly, the local engine shop can do an IRAN for 6250. plus parts. In the interest of protecting my sanity I may just have the shop tear the whole thing down so I can be assured it is all within spec and serviceable. I am not blaming my issues on the C/R but I am contemplating returning to stock to see if this might help.
Sorry for the long winded post. Not doing any of this to be a Karen or throw a shop under the bus. If anyone else has had problems with a low time engine you are not alone.
Thanks!i
 
Last edited:
I'm betting most of us would not find them disturbing. :)

This is the exterior obviously. The borescope pics are the usual hammered piston and cylinder stuff. I am grateful this happened on the ground and that it went out of the top of the cylinder and not through the top of the piston where it would have done more damage. The exhaust valve looks untouched.
Kinda new to piston engine aircraft ownership. I've had gliders for the past 20 years and only about 2300 hours of piston time and except for a stuck exhaust valve on an 0-360 power Scout I've never had any issues. I figured I would buy a plane with a well documented engine and stay within Lycoming limitations and careful maintenance I would be OK. So far during disassembly there is nothing to indicate any corners were cut.
 

Attachments

  • 20220610_142312.jpg
    20220610_142312.jpg
    275 KB · Views: 242
Last edited:
Stuck intake valves are pretty uncommon. The fact that you had one, as well as another broken one, I suspect someone left the valve guides too tight. They are installed undersized and reamed to proper size by the installer. Possibly a bad batch of valves. I would wash my hands of those cylinders and start fresh with new or have them overhauled by a good shop with all new valves and guides.

FYI, you don't get poor compression from having the ring gaps lined up. Highly pressurized air will turn a sharp corner almost as easily as going straight through two gaps. Rings are always moving and it is not uncommon for the gaps to be aligned at various points in there service life. If that were a real issue. the manufacturers would have installed something to keep them from rotating. Yes, we install them offset and hope they rotate at the same rate, but often they don't.

Larry
 
Last edited:
FYI, you don't get poor compression from having the ring gaps lined up. Highly pressurized air will turn a sharp corner almost as easily as going straight through two gaps. Rings are always moving and it is not uncommon for the gaps to be aligned at various points in there service life. If that were a real issue. the manufacturers would have installed something to keep them from rotating. Yes, we install them offset and hope they rotate at the same rate, but often they don't.

Larry

+1. While having the gaps line up might result in a small dip in compressions, the usual recommendation is to fly and re-test. Doing a top overhaul because the ring gaps lined up was very poor advice.

PS. There are several DARs on this forum. If you change the title to “Back to phase 1?’ Or something like that, one of the DARs might offer his opinion.
 
Last edited:
The Repairman certificate lets the holder sign off the annual condition inspection. Period. Nothing else. Anyone may legally work on an EAB aircraft. Experimental engine, data plate means nothing. The only legal question is whether or not this is a major change, requiring a return to phase 1 OpLimits. Best not to guess: ask a DAR or call your FSDO.

Thanks for the clarification on the "repairmans" certificate. Learning everyday!
 
This is the exterior obviously. The borescope pics are the usual hammered piston and cylinder stuff. I am grateful this happened on the ground and that it went out of the top of the cylinder and not through the top of the piston where it would have done more damage. The exhaust valve looks untouched.
Kinda new to piston engine aircraft ownership. I've had gliders for the past 20 years and only about 2300 hours of piston time and except for a stuck exhaust valve on an 0-360 power Scout I've never had any issues. I figured I would buy a plane with a well documented engine and stay within Lycoming limitations and careful maintenance I would be OK. So far during disassembly there is nothing to indicate any corners were cut.

Gruesome indeed. Like you said though, good thing it came out the cylinder limiting the damage.
 
The Repairman certificate lets the holder sign off the annual condition inspection. Period. Nothing else. Anyone may legally work on an EAB aircraft. Experimental engine, data plate means nothing. The only legal question is whether or not this is a major change, requiring a return to phase 1 OpLimits. Best not to guess: ask a DAR or call your FSDO.
Agreed, except - depending on the vintage of your plane and specifically your Operating Limits, it may be simplest just to treat it as a major change. For example mine say after a major alteration I need to fly 5 hrs without passengers day VFR over unpopulated areas and log it. When I switched from Mags to P-mags I just did that rather than try to verify if it actually constituted a Major alteration. For me it was no hardship (dang, I have to go fly for 5 hrs!) and less trouble than bringing it to the attention of the FSDO (especially during Covid when they're all "working" from home i.e. not accessible). However some OpLims have different language so see what those say first.
 
Problems

Not all "reputable shops" are created equal. In my opinion it is highly unlikely that "9.2" compression had anything to do with your problems. I am running 10-1 on my 0 320 with zero problems at the 100 hour mark.
The shop that I respect the most told me long ago that a 10/ 1 engine with all the other typical mods will go about 8-900 hours with no problems when flown hard, as in world unlimited aerobatics. At that point bearing wear will cause deteriorating oil pressure and its time for an overhaul. This is applicable to any of the parallel valve Lycomings.
The problem history your engine has experienced is almost unheard of in the aerobatic world where engines are run MUCH harder than yours.
In my opinion it is highly unlikely the engine was properly assembled.
The 9.2 pistons are probably standard Lycoming 0 320 H model pistons which give 9-1 compression in the non H 0320's. That was a very standard mod in the era of the original Mattituck.
Given the multiple problems I would recommend a complete teardown.
 
I don’t see a top overhaul as a major change. It’s just maintenance.

+1

Changing compression is like changing the amperage capacity of an alternator. Not something requiring flight testing or affecting flight characteristics. Phase I is for changes that affect flight characteristics, like weight, prop type, control surfaces, etc.

I called the FSDO when going from Carb to FI, just to be sure. They told me NO major or minor change. Be advised that the op lim's reference various FARs as guidelines and therefore a test flight and sign off, is strongly recommended after this type of work.

Larry
 
Here is my opinion. I have been flying behind lycoming engines for 50 years. I’ve heard plenty of stories of problems with overhauled cylinders. Any good quality major overhaul to new limits normally has new cylinder assembly’s. If they want 6250 for an Iran plus parts, check on brand new cylinder assembly kits at Air Power. Might not cost you any more and you will know what you got on the top end. Bottom end on your engine could be a different story.
 
Thanks for all the insights. I haven't discussed overhaul VS new (With the shop) for cylinder assemblies, but I know I will need at least one new one. They are so cheap that it won't take much arm twisting to replace the other 3. Bad news is the turn around time. Could be a long summer....
Kirk
 
Last edited:
Thanks for all the insights. I haven't discussed overhaul VS new (With the shop) for cylinder assemblies, but I know I will need at least one new one. They are so cheap that it won't take much arm twisting to replace the other 3. Bad news is the turn around time. Could be a long summer....
Kirk

Part source selection aside, be sure you determine why your intake valves are sticking - it could be dimensional, but also consider valve guide material, and top end lubrication on this engine. Having one stick is a possible rare thing - to have two is an indication of a core issue. Just make sure it is eliminated.

How parts look, wear, polish, scuff, etc will talk to you. Have good engine guys look at the parts to read what might be happening. Is/was material transfer to the valve stem present ? Stem scuffing? Are rocker bores indicating lack of lube?
Pushrod tips?

Edit: One thing that will break stems fracture faces and break keepers is seating velocity of the valve. This can be due to a bad cam grind and/or excessive clearance. In spite of the fact that valves seem to move rapidly. Just be aware that IF this is your issue, failures will happen again with new valves, overhauled or new cylinders.

Good luck.
 
Last edited:
Thanks for all the responses! Just into the initial teardown stages and found the intake valve keeper to be the culprit. No idea what caused this. The valve was in 3 pieces in the carb and intake. The other 3 cylinders look good.
I've contacted one recently retired DAR and one current DAR and they both said changing the C/R is not a major change. The pistons appear after market with some numbering but no manufacture name. Right now I'm planning 8.5 to 1 stock pistons for 160HP. The data plate says 175HP but who knows how that was determined. So...if we take 2-4 percent per point of C/R a minus .7 we get 1.4 to 2.8% decrease. Using the (Unsubstantiated) 175 @ 2700 per the data plate the most HP I would loose could be 4.9. I am limited to 2600RPM due to the prop so I doubt it is even that much.
I have been offered a Catto prop recently which would bring the PRM back to 2700. The plane currently makes the Vans cruise numbers with the Metal Sensenich but it likes runway.
Thanks,
Kirk
 

Attachments

  • 20220617_112907.jpg
    20220617_112907.jpg
    366.2 KB · Views: 213
  • 20220617_122342.jpg
    20220617_122342.jpg
    487.8 KB · Views: 216
Last edited:
I don’t pretend to be an expert, but given the extent of the damage shown in your photos, in addition to the piston and cylinder I’d be concerned about the connecting rod. If it was overstressed and bent, you are at elevated risk for a potentially catastrophic failure down the road.

Be safe!
Peter
 
Last edited:
Pete,
You are spot on. I've had a couple of long talks with the shop and they treat stuff like this similar to a sudden stoppage. The rods will be measured (Which I think they do anyways) and the crank will get the full treatment. Dye penetrant on all the aluminum parts and eddy current on the steel stuff (I may have that backwards).
Good news is that the IRAN includes the carb and mag. They found an issue with the carb even before tearing it down. I'm learning a lot just from talking to the guys and seeing the parts.
Kirk
 
Thanks for all the responses! Just into the initial teardown stages and found the intake valve keeper to be the culprit. No idea what caused this. The valve was in 3 pieces in the carb and intake. The other 3 cylinders look good.

IMO, and I'm not an expert, I would want an answer to what caused the keeper to fail. The proximate cause is seldom the root cause of a failure.
 
Back
Top