SonexBuilders.net

It seems that all Aerovees have valve issues, I know mine has exhaust compression loss every 100 hours, give or take. When I take my heads off I have a huge build up of lead from the 100LL avgas. I wonder if the lead is the cause of the exhaust valve leakage? Question: Do the Aerovees that run on auto fuel have the same valve issues that 100LL fuel causes? Do others mix auto and avgas? For those of you who don't have issues with valves, what's your secret?

Thanks,

Ken W
Sonex 959
Aerovee 8:1 compression 310 hours

I'm curious to know more about the valve issues. I've got about 100 hours on mine and wouldn't be concerned about the valves were it not for the recent posts on this forum.

Do you discover the compression loss with an actual compression check or from engine instruments? Is it a loss that you can feel when you turn the propeller by hand? I ask because I haven't yet performed an actual compression check, but I do turn the propeller by hand pretty regularly--thinking I'd be able to notice if one cylinder was a little off from the others.

Is removing the head the only way to really check the exhaust valves? Can you remove the exhaust and see enough that way? Does anyone have a borescope they recommend for the spark plug hole?

If this really is an issue that affects all Aerovees, do VWs in cars have the same problem? I would think that keeping CHTs low would keep the valves cool (mine are typically <350 except one that occasionally gets to 400 in climb).

Hrmmm...

"Huge buildup of lead" sounds to me like a mixture issue. What kind of leaning do you do? Where do you fly (elevation, temperature, humidity, etc"?

Wayyy more information is needed before one can make blanket statements about the cause of the problem, or what is required to fix it. In the meantime, I suggest you check out some of the following EAA webinars:

http://www.eaavideo.org/video.aspx?v=2149054014001
(Engine health and compression)

http://www.eaavideo.org/video.aspx?v=2274677932001
(Engine leaning)

http://www.eaavideo.org/video.aspx?v=972961455001
(Engine Troubleshooting)

http://www.eaavideo.org/video.aspx?v=2897547338001
(TBOs and Maintenance intervals; including engine condition inspections)

http://www.eaavideo.org/video.aspx?v=1204537102001
(All about Cylinders)

http://www.eaavideo.org/video.aspx?v=3817526267001
(Exhaust valve failures)

--Noel

I should not have opened the can of worms by say "It seem that all Aerovees have valve issues". I apologize for that. "I" have had exhaust blow-by issues every 100 to 150 hours. The only thing I can think is that the 100LL buildup (bottom of no.3 had almost 3/16" in one spot and 1/8" the rest of the head) is keeping the exhaust valves on the hottest cylinders from closing. That is why I was asking if the owners using auto gas have the same buildup.

I lean in cruise to 1330 avg. Never over 1350. I lean on cylinder #1, #2 is 20 degrees cooler, #3 is 50 degrees cooler and #4 is 70 degrees cooler. All EGTs are within 100 degrees. CHT on #3 in the summer, in Iowa, 1000' airport elevation, 90% humidity, low 380's max. Low 370's this time of year. Climb-out I don't like getting over 400. I shallow my climb and throttle back before I get there. CHTs, #1 is 15 degrees cooler, #2 and #4 are 25 degrees cooler.

I lean after startup and during taxi to highest rpm.

Maybe I am leaning improperly.

I will check out the videos. I have tried different fixes to lower the CHT on #3 to no avail. Cylinder head dam on #4, opening the cowl outlet, smoothing out the top lip on the cowl, resealing the baffle.

Ken W

I also have had a lot of lead buildup, so I'm now using TCP in the fuel to try to lessen that. I also leaned aggressively. But when I pulled the head after an exhaust valve leak, the local VW mechanic thought that was due to over-leaning. Now I run EGTs in the upper 1100s rather than mid 1300s.
Bill

billmaxmcw wrote:I also have had a lot of lead buildup, so I'm now using TCP in the fuel to try to lessen that. I also leaned aggressively. But when I pulled the head after an exhaust valve leak, the local VW mechanic thought that was due to over-leaning. Now I run EGTs in the upper 1100s rather than mid 1300s.
Bill

I think both of those are the best advice. I also use TCP and have not had lead fouling issues, though I certainly see lead on the tops of the pistons. There was no lead evident on my valves when I pulled the heads after 80 hours. I also had been leaning, but with the burned rear valves recently my machine shop guy also thought I was leaning too aggressively. I have been cruising at about 3.8 gph. I'm planning to richen that a bit to get to at least 4 gph or more.

Due to my back injury I didn't fly all winter. And the Sonex sat for a good 6 or 7 months. When I started it had a very bad skip to it. I checked everything and while it was running it started leaking oil very bad. I looked under it and the push rod tube was bent and leaking oil. I pulled it apart to find a broken push rod and stuck exhaust valve. It. Was so tight in the valve guide. Took to my local machine shop and had a both heads completely gone thru. Not sure what exactly caused the valve guides to tighten up but its all back together and running great. With great temps. My egt gets a little high on climb out but I just bring the throttle back a bit and they stabilize .
Adam Simmons
Sonex 541

By the way I have a Revmaster. 2100 which just hit 100 hours. ,I have had no major issues with the Revmaster and I highly recommend them. Also the customer service is great with Revmaster

billmaxmcw wrote:Now I run EGTs in the upper 1100s rather than mid 1300s.
Bill

How many hours have you been running this way and what are your results? How many GPH did you give up moving to 1100s?

Sonex541 wrote: I looked under it and the push rod tube was bent and leaking oil. I pulled it apart to find a broken push rod and stuck exhaust valve.
Adam Simmons
Sonex 541

Next time I order some parts I'm considering getting these:
http://www.mofoco.com/item/EMPI_9096_VW ... _TUBES/496

If I ever have an issue requiring replacement of the push rod tubes, seals or push rods, I won't have to take off (or loosen) the heads. Of course they don't help if you have to remove the heads to do a valve job.