What I learned about valves

[mike.smith]

So with 80 hours on my AeroVee I ordered a complete set of valves for both heads, and new head gaskets.

I took the second head off today, and I found the same discoloring of the #1 valve guide and staining of the head around the valve stem, that I saw on the #3 of the other head. The leak down on #1 wasn't bad, but it looks like it was going to become a problem in the near future.

The colors of the valves and heads looked about right for the forward #2 and #4 cylinders, while the rear ones were certainly blacker and rougher.

Someone from the Sonex forum emailed me privately and said he had the same thing happen at 75 hours, and he felt it was pretty common for VWs. If that's the case then that sucks! There are not many places you can have an induction leak in the AeroVee (and I verified all my connections were TIGHT), so it makes me wonder about other possibilities:

1. When I was trying to get my carb dialed in at the beginning it was running super lean. It took me a while to figure it out and correct it. Maybe this all started back then?

2. The 1-into-4 induction system is pretty crude, so maybe the intake path just doesn't flow well to the back cylinders, and they are perpetually lean. Makes me think I should run a little richer just to compensate.

3. Makes we want to consider fuel injection.

That #3 must really have been underperforming, so I'm looking forward to the valve job and the potential for getting the engine actually producing full power.

Lesson learned: whenever you go inside your rocker covers, look at the base of the valve stems. If the valve guides are discolored (red/orange instead of gold/bronze color) and/or there is brown/red discoloration on the heads, around the valves, you have an overheating valve and you need to investigate.

So I learned something :-)

[Brett]

Regarding your number 2 point, I am hoping the turbo engine will produce a more uniform mixture all round. My aerovee had the same problem at about 50 hours. I just replaced both heads however with new ones. I had a lot of early overheating issues and that more than likely caused it. I will find out soon enough I suppose when I get the new engine running in the Sonex.

[Rynoth]

Just to add a note here, during assembly I discovered a valve that was seating very poorly (not sealing) in one of my kit heads. I sent the head back for replacement and the new one was much better. Might be some QA issues with the heads, I'd encourage anyone building an Aerovee to get some form of compression tester to verify you have a good set of heads/valves during assembly.

Here's a link to my thread discussing it. viewtopic.php?f=7&t=1709&p=13670&hilit=valve#p13670

And a picture of light I saw passing the valve on a brand new head.