seabee

I have noticed on a couple of my engines that when they initially start
there is slight leakage between the cylinder head and cylinder but it stops
as soon as they get hot. When cold the cylinder head bolts appear to be
tight. Is this just how things are or do I need to do something?

Seabee

david

Hmm. Fit a (new) gasket?

Torque the bolts up when the head is hot...the shanks will be a bit longer
and you'll get a good tight fit.

paul mcintosh

Torquing bolts when hot will cause them to be looser when cold. The
aluminum expands a lot more than the steel bolts.

Torque them when the engine is cold and the holding force will increase as
the engine heats up.

--
Paul McIntosh
Desert Sky Model Aviation
http://fly.mcintoshcentral.com

paul mcintosh

This is usually cause by a warped head or bad gasket. four-bolt, cast
Supertigre engines were famous for that.

Replace the head gasket and CAREFULY tighten the screws in a crossing
pattern. Start out by holding the head flush with your fingers as you bring
the screws down until the heads JUST make contact with the head. Then
tighten each one about 1/8 turn at a time until they are tight.
--
Paul McIntosh
Desert Sky Model Aviation
http://fly.mcintoshcentral.com

seabee

Thanks for this.

Gaskets now on order.

Seabee