Sonex-A purchase - What to look for

[rwthomas1]

Daleandee touched on the point and it seems it may have been missed. An exhaust valve cools when it is on the seat. The seat, the margin width, and how good the valve job is will play a large role in how cool an exhaust valve runs. If I was to setup a set of heads for this kind of use, a margin a good bit wider than the minimum would be good. Along with any sharp edges before and after the seat area smoothed out as much as possible. Sharp edges attract heat. Not trying to step on any toes, but the devil is in the details for valve setup on highly stressed engines.

[BRS]

... Not trying to step on any toes, but the devil is in the details for valve setup on highly stressed engines.

Well if it's the devil's toes you are stepping on, I say do it, in fact, stomp don't step. We need more of that these days. ;-)

[Hambone]

So what would you modify or check on a new set of heads from Sonex?

[Kai]

So what would you modify or check on a new set of heads from Sonex?

Following!

[BRS]

There is a company that makes some slick looking water cooled head/cylinders for lycoming. Something like that for the VW might be fun.

While the heads are off, some folks like to go at them with a round file, hack-saw-blade etc and open up all the little blocked castings around exhaust side of the head. Get a path for all that cooling air to flow through.

[karmarepair]

So what would you modify or check on a new set of heads from Sonex?

The current production Sonex heads are really nice. All the air passages are clean and crisp.

I'd get busy on the baffling. I don't have the link handy but if you go to the EAA builders log website and search for the Lawrence Sonex near Concord CA you'll find my plane, and you can see what I've done.

[Hambone]

So what would you modify or check on a new set of heads from Sonex?

The current production Sonex heads are really nice. All the air passages are clean and crisp.

I'd get busy on the baffling. I don't have the link handy but if you go to the EAA builders log website and search for the Lawrence Sonex near Concord CA you'll find my plane, and you can see what I've done.

Will do. Thanks!

[Kai]

Check that the crankshaft has the smaller ø20mm prop flange bolt, and not the bigger one.
Get the prop dynamically balanced.
Find a proper place for the 4 cht sensors like shown on these pages previously.
Be very suspicious if you ever see the cht at anything much above 300F.
Check the ignition system for proper timing. When done, check it again.
Get hold of very high quality valves. If you´re not very comfortable with cutting seats and grinding in valves and seats yourself, take them to someone who is.
If the carburettor has a leaning device, always keep the A/F ratio below 12.5-12.8
Make sure that your cooling air plenum and baffeling is super tight. ALL the air must go where it cools- especially on the underside of the heads..
The exit lips on the air outlets in the cowling like suggested by Sonex must be in place. At least make them so wide that the the lower edge is flush with the bottom of the fuselage floor. Even better extend the cowling outlet channles back to the firewall. As an alternative you could also put side outlets in the cowling- mine made a real difference.
And finally- run the engine exclusively on good quality high octane fuel. Detonation will kill it faster than anything else.

[BRS]

...
Get the prop dynamically balanced....

Kai - i own a balancer and have balanced many larger props with a spinner, backplate, ringgear, but I've never figured out a place to put weights on my little Prince prop. Any advice?

[Kai]

To dynamically balance my Sensenich fp 2-blade, I put a prop spacer between the backside of the prop and the engine drive flange, I seem to recall that a 1 inch thick one from Sabre Mfg was sufficient. In this one I drilled and threaded 6 pcs 1/4 inch holes diametrically placed exactly between the holes for the prop bolts. Find 6 round head machine screws that are so long that they reach from the outer diameter of the cowlings prop opening to the prop flange boss. Go and buy a stack of 1 inch diameter flat washers, something around 1.5-2 mm thick. Start the balancing process by attaching washers to the machine screws and secure with thread lock. Voila! The weather is absolutely dismal here now, but should it ever stop raining I´ll get out to the airstrip an take a picture,