Stripped Plug and Low Comp

[Weatherpilot]

So, In my new to me Sonex I was changing plugs and doing a condition inspection. (with my mechanic) Cyl #3 has 4psi and can hear air escaping from the exhaust. Bad/dirty/funky exhaust valve I'd guess. Also, some previous person ham-fisted the top plug in pretty much stripping it. I want to replace the head on that side to fix the stripped plug. I know there are repair kits things that can be used but I would feel better with a solid head. So while I'm at it should I do both? The cylinders are in good shape. Borescoped and looking good.

What is a good source for new heads? Sonex? Other? Any recommendations welcomed.

Thanks,

Greg.

[Bryan Cotton]

I'd repair the head with timeserts.
viewtopic.php?f=7&t=3948&p=29996&hilit=Timeserts#p29996

But if I was buying new heads, I'd go to Sonex.

[daleandee]

I'd repair the head with timeserts.
http://www.sonexbuilders.net/viewtopic. ... rts#p29996

But if I was buying new heads, I'd go to Sonex.

Agreed! Do the timeserts and lap/grind the valves as needed. Save the real money for gas ... 8~)

[Bryan Cotton]

It's my understanding that the timesert is better than a solid head. It's a steel insert locktited in, and the plug replacements are all steel on steel. If I had known about it when we built our Aerovee I would have done it proactively. Since then I bought the kit and will do it at overhaul.

[Weatherpilot]

So I have decided to replace the head with the stripped out plug hole and sticking valve. Sonex has them for about $550 + shipping. I looked around and see that MOFOCO and EMPI have heads for about half that cost. MOFOCO will even do second spark plug for $100 additional. Anyone opt for the MOFOCO or EMPI heads? Experiences? Which one do I get for the Aerovee? Any help appreciated.

Greg.

[bvolcko38]

MOFOCO heads came with early Aerovees. I don't know why Sonex switch suppliers.

[Area 51%]

MOFOCO heads came with early Aerovees. I don't know why Sonex switch suppliers.

CB Performance heads can be found on an early Aerovee engine. The factory prototype Xenos came with these. Very nice high quality heads, but don't tell CB what you are using them for.

[Weatherpilot]

Which type head do I get from these places? They have several variants.

[Area 51%]

Which type head do I get from these places? They have several variants.

92mm cylinder openings with 40mm intake valves.

[kmacht]

Even if you replace the head you should still consider installing timeserts. The aerovee tends to build carbon on the end of the plug and when you go to remove it that carbon binds the plug and strips out the aluminum threads in the head as the plug comes out. It’s likely that the original builder didn’t ham fist the plug in and instead you ended up stripping the threads yourself when you tried to remove the plug with the carbon buildup. There isn’t really any fix when the carbon starts to cause the plug to bind other than pulling the head and trying to remove the carbon buildup before unscrewing the plug further. The timesert essentially turns the spark plug threads from aluminum to steel and since the steel is harder than the carbon buildup it will push the carbon off when you unscrew the plug. I borrowed the timesert kit from a fellow builder and put them in my heads during a rebuild. It was very easy to do.

Keith
#554