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I developed a burned valve in my original MOFOCO heads. After doing the research as well as speaking to Sonex, I decided to replace them with EMPI heads and bought them from Sonex already machined for dual plugs.

Once they arrived, my friend did a 3-angle valve job and ported and flowed them. I reinstalled the original rocker arm assembly. The engine ran like never before. Don't use the MOFOCO's. The EMPIs are superior.

I'm doing the first condition inspection since getting the AWC, just less than 50 hrs TT, and I had a difficult time removing several sparkplugs that were removed an reinstalled quite easily at 5 hrs. Later today I'm gonna scope the holes and have a look. Assuming I need to install timeserts, can anyone say for sure if its the M12 x 1.25 15 mm or 17.5 mm insert that is required? I see both lengths mentioned in different posts. Not happy about having to pull the heads on a engine that is running great. I'm also curious if this is a warranty issue. Any advice or warnings for installing timeserts?

peter

15mm is what I used and they worked fine. The process really is simple and fairly foolproof. The factory really should be installing them as standard features when they modify the heads for the second set of plugs. There are a few air cooled vw online stores that will rent you the installation kit to save you some money. I think it’s under $50 to rent the install kit plus the cost of 8 inserts.

Keith
#554

In my original MOFOCO heads, I installed TimeSerts for the same reasons everyone else does. The MOFOCO aluminum casting is just softer than the EMPI and the plugs strip easily. Doesn't matter if you use plug lube or not. Yes, Sonex should have them installed when they drill for dual plugs.

The TimeSerts worked great. I did not even have to remove the heads to install them. Just rotate the prop to get both valves closed, heavily grease the drill and tap tool, and install them according to directions. The grease captures any shavings from the drill and tap procedure. A machinist friend of mine taught me that trick and has been using it for decades in Harley engines. Make sure to blow out the cylinder after each insert and scope them just to be sure. I had no issues.

Here are a few photos of #3. Ugly. # 3 runs the hottest. #4 has a little of this as well. #1 & 2 are very clean in comparison. The damaged thread shown is for the bottom plug. The top thread is clean. Note the small collection of scale at the edge of piston on the cylinder wall...it is right below the thread and presumably broke free of the plug when I loosened it.

I plan on pulling the heads to install the timeserts and take a closer look. I am very curious to know why 4 cylinders can looks so different. Comments and observations welcome.

peter

Weatherpilot wrote:Cyl #3 has 4psi and can hear air escaping from the exhaust.

Update to my dilemma:

I removed the valve cover thinking maybe the exhaust valve wasn't closing all the way. Nope, valve looks like it is operating normally when turning the crank by hand. Perhaps some carbon or something is allowing pressure to escape? Going to borescope to see what is in there. My next step is to start it up and see if it improves. It has been sitting for a while so maybe a start and lean idle might help?

Weatherpilot wrote:

Weatherpilot wrote:Cyl #3 has 4psi and can hear air escaping from the exhaust.

Update to my dilemma:

I removed the valve cover thinking maybe the exhaust valve wasn't closing all the way. Nope, valve looks like it is operating normally when turning the crank by hand. Perhaps some carbon or something is allowing pressure to escape? Going to borescope to see what is in there. My next step is to start it up and see if it improves. It has been sitting for a while so maybe a start and lean idle might help?

You can pressurize the cylinder to find where the leak is coming from. It's easy enough to say it is the exhaust valve but I've found intake valves to leak when carbon or lead got in the way of the valve closing. If it is a valve you may be able to stake the offending valve and get better compression numbers.

FWIW,

Dale 3.0 Corvair/Tailwheel

Simple question but after pulling the valve cover did you also check the rocker to valve stem clearance and if so, what were they at? The valve stems tend to stretch a little bit over time and can close up the .004-.006 gap that is supposed to be between the valve and rocker arm when fully closed. If you have no gap on that valve it could be holding the valve just slightly open. If the gap is much bigger than .006 it could be that you have a piece of carbon holding the valve from completely closing.

Keith
#554

Good recommendation. I will be adjusting the valve clearances per the Aerovee assembly manual and then run the engine to see what that does. Like I said in the original post - this thing ran fine but did sit for 10 months in tiedown. Going to run it and see if things improve.

Thanks for all the great advice.

Greg.

Did the valve adjustment yesterday. I was surprised to discover the valve covers although safety wired were finger tight on the bolts that hold the cover. After the valve adjustment cleaned the covers and replaced the gaskets with new ones. Also put in new grommets on the bolts as the ones that were in there were the wrong ones and broke apart when I removed the valve covers. Discovering a lot of loose things on this motor. Plugs finger tight. Other items not tightened down properly too. Going to keep going over this engine with a discerning eye.

Updates to continue.

Greg.