Brand new cylinder head problems

[Rynoth]

Were you able to fix the original heads you had (the one with the valve seat issues), or were those to far gone to be repaired?

I didn't try to fix the original new heads , I sent them straight back and Aeroconversions sent me replacements which is what I have now and did the lapping on. I couldn't say if lapping would have solved my original issue of the VERY leaky valve since I didn't try. I also didn't have a compression tester for the originals but I wouldn't be surprised if it would have read darn near zero.

[MichaelFarley56]

OK. Possibly a rube question. But I see US made performance heads with port and polish and sized to cylinder specs. Sure twice the price - but I'm imagining (possibly wrongly) that worth paying for less hassle?

https://www.mofoco.com/category/Performance_Heads/c52

Graeme, one of the issues we would have on an AeroVee by purchasing our own heads is the secondary spark plug hole that Sonex has machined. I don’t know which shop does that work for them but I have no doubt it’s an aftermarket shop that takes their heads and performs that work before they’re sold to us.

[GraemeSmith]

Graeme, one of the issues we would have on an AeroVee by purchasing our own heads is the secondary spark plug hole that Sonex has machined. I don’t know which shop does that work for them but I have no doubt it’s an aftermarket shop that takes their heads and performs that work before they’re sold to us.

It's an option on some of the heads on the site I mentioned:

Machine Head for Dual Plugs
Dual 12mm Spark Plugs $100.00

[Area 51%]

Quite a few machine shops out there will add the second spark plug hole...once you find them.

I deal with a shop in Michigan that does outstanding work. Great Plains will do it as well. The real trick is to start with a high quality head, and that doesn't necessarily mean made in the U.S.A.

Made in China doesn't mean they are all bad either. I've been running a set of Chinese heads on my car for 3 years and 35K miles without a single glitch.

[WesRagle]

Hi Guys,

Just finished putting the new heads on yesterday, luckily leak down was good and no issues so far.

I know several people do this every other year or few hundred hours;

From Barn Stormers:

"Legacy Model "Red Tail Squadron" themed. Tri-Gear, 115 hrs. TTSN, Always Hangared at KMRT (central Ohio), Aerovee 80 HP, New EMPI Heads installed during annual 8/2019."

These types of problems go on and on. Seems to me it all begs the question: Whats wrong?

Are we operating the engines wrong? Are VW heads just not up to the task? Or, where can we get heads that are up to the task? What is it?

Is it the lead in the fuel? I know Scott Casler of Hummel Engines says specifically to use TCP if you burn 100 LL in his engines. I really want to believe that the VW can be a reliable/economical engine but the problems with valves/heads just keep coming.

I do wish someone with the knowledge would step up and say "Do this, then this, and then this and you'll have a top end that'll last."

Also, at the risk of offending some, I think it is just wrong to sell engine parts that may or may not be ready for use to the average Joe (someone like me) all the while emphasizing that if you can build an airframe you can build this engine. There is a world of difference between sheet metal and machine shop skills.

My Thoughts,

Wes

[GraemeSmith]

Is it the lead in the fuel? I know Scott Casler of Hummel Engines says specifically to use TCP if you burn 100 LL in his engines. I really want to believe that the VW can be a reliable/economical engine but the problems with valves/heads just keep coming.

I do wish someone with the knowledge would step up and say "Do this, then this, and then this and you'll have a top end that'll last."

Lead will gum up the valve guides and get you stuck valves - Continentals suffer from this. Personally I used TCP and leaned aggressively - which kept me good there. I'm 30 hours into the new to me plane and running TCP - the oil change on Saturday - the oil was pretty clean - leading me to hope most of the lead is going out the tailpipe because of the TCP - just like the Continental.

Reliable heads - I wonder how many go "soft" through being run hot. There is a critical point on aluminimum heads. Break 450F and the heads wear far faster and tend to warp. And there goes the head seal. If there is one thing I'm trying to be enormously careful with - it is not over temping the heads.

Mike Busch has a pretty decent article about it here:

https://blog.aopa.org/aopa/2016/10/19/t ... mperature/

[WesRagle]

Mike Busch has a pretty decent article about it here:

https://blog.aopa.org/aopa/2016/10/19/t ... mperature/

Interesting read.

So, our first concern should be CHT if we want top end longevity.?.? Other than mixture control, some things that come to mind.

1) Since these are experimental aircraft we do have the option of varying the cowl inlet and/or outlet to reduce CHT.

2) I think it's common with VW heads that there is a lot of flashing between the head cooling fins left over from casting. That flashing should be removed to help reduce CHT.

3) Make certain that the baffling is well sealed.

I am installing a Hummel and burning 100LL so I'll follow Scott's instructions and use TCP fuel additive. Another interesting comment in the documentation delivered with my engine is: "This should be a 1000-hour engine except for leaky valves due to not running for long periods of time". Don't fully understand the statement. Maybe someone can clue me in.

I will have 4 cylinder monitoring of CHT with the warning set to go off at 400 Deg. F. I'll make sure to keep cruise CHT down to 350 Deg. F. Those are the temperatures I used with the AeroVee and it seemed to serve me well, but I only operated that engine for about 150 Hrs.

BTW, that brings up another issue. CHT probe installation is not standardized with VW engines. On the AeroVee I had the CHT probes installed under the spark plugs. What a pain. I have been told that that is the hottest place to install them, which is good, but for a number of reasons I will be screwing the probes to a cooling fin this time. I need to research where to attach them for hottest reading *and* if I should reduce my CHT limits as a result of moving the probes. The running joke back in the day was: "If your CHTs are too high, move the probe". Not so funny given all the problems folks are having.

Edit: Sonex LLC has guidance on where to install the probes. Ref. http://www.aeroconversions.com/support/instruction_sheets/CHT_Install.pdf

Anyway, what else? What else can we do to help the situation?

Wes

[dirkverdonck]

Hi All,
The Aerovee and all other VW conversion engines that use the standard VW cylinderhead will somehow be CHT limited because the cooling fins of these heads were designed for a 40 bhp enngine that seldomly had to deliver full power in road use.
Upping the output to the double of that, max 80 bhp will thus lead to overheating whatever you do.
I have about 100 hrs on my Aerovee now and I make sure that I reduce power as soon as possible after T/O and climb at 80 to 85 kias with an overrich needle setting.
My CHT seldom go over 350°F and I watch those continuously. In cruise I can lean and I keep the EGT below 1100°F ( I use extra fuel to cool the heads for T/O and lean afterwards)
I have so far never used 100LL but only use the highest octane car gas I can find at the gas station next door containing between 5 and 10% of alcohol.
I keep the aircraft grounded when OAT is over 100°F as my CHT and oil temps go into the red in these conditions and the engine quits on lower power setting during the descent and final approach.

Just my thoughts, do not expect the impossible from an engine designed in the fourties with an output less than half what the Aerovee delivers on T/O

[Onex107]

I had one cylinder with a low leak down pressure. I did lap the valve by removing the spring and keepers and chucking my electric drill on the end of the stem and rotating it both directions with lapping compound on the valve face. The hand lapping tools are rolled back and forth between your hands and it's difficult to keep pressure on the valve seat. Valves have a metal to metal seal. The valve and seat have to be perfectly round and the valve guide perfectly centered to the seat. The slightest bit of dirt will cause a bad leak. Don't assume bad machining is causing the leak. The guy assembling the valves may have had dirty gloves. The valves may have been lapped during manufacture and some of the abrasive is still there. A quick touch with compound/ or running the engine before testing, if you are assembled, may make the problem go away. When I do the condition inspection I always do it on a hot engine. 280 hours and flying.
Sealing the cylinder and testing the lapped valve off the engine saves the assembly time if it needs more lapping.

[ScottM-Sonex1629]

Hi Guys,

Just finished putting the new heads on yesterday, luckily leak down was good and no issues so far.

I know several people do this every other year or few hundred hours;

From Barn Stormers:

"Legacy Model "Red Tail Squadron" themed. Tri-Gear, 115 hrs. TTSN, Always Hangared at KMRT (central Ohio), Aerovee 80 HP, New EMPI Heads installed during annual 8/2019."

These types of problems go on and on. Seems to me it all begs the question: Whats wrong?

Are we operating the engines wrong? Are VW heads just not up to the task? Or, where can we get heads that are up to the task? What is it?

Is it the lead in the fuel? I know Scott Casler of Hummel Engines says specifically to use TCP if you burn 100 LL in his engines. I really want to believe that the VW can be a reliable/economical engine but the problems with valves/heads just keep coming.

I do wish someone with the knowledge would step up and say "Do this, then this, and then this and you'll have a top end that'll last."

Also, at the risk of offending some, I think it is just wrong to sell engine parts that may or may not be ready for use to the average Joe (someone like me) all the while emphasizing that if you can build an airframe you can build this engine. There is a world of difference between sheet metal and machine shop skills.

My Thoughts,

Wes

Wes:

I don't know what to tell you about my experience. That is my ad on Barnstormers. The engine runs great and has over the 3 years I have been flying it (minus some self inflicted leaning problems a few years ago).

Mike Farley was assisting me with my annual this year (at least the compression/leak down check) and we ran the engine, tested the compression and #1 and #3 would not pass. (50/80 and 28/80 respectively). It still ran great though. So flew the plan for another hour+, and retested. #1 came up to 59/80, but #3 is only 29/80. So I could try to take the heads off, mess with machining the valve seats, and throwing "parts and time" at the heads (the older MOFOCO heads)...which my wife said what happens when it still doesn't pass the compression check, and the answer was this: go ahead and buy new heads and save the time and risk.

I will be lapping the new valves/seats into the new heads when they arrive.

I have been communicating with a possible buyer for my Sonex, who is an A&P in the armed forces, and he appreciated my honesty and approach to how I am addressing MY airplane/engine during the annual. The cost is relatively minor considering the cost of my life or someone else's.

YMMV,
Scott