Measuring crankcase pressure

[astjp2]

how to use an airspeed indicator to measure your engines crankcase pressure

[astjp2]

More on this...

[PA1195]

Is there a correlation between leak down cylinder tests and elevated crankcase pressure? How about exhaust valve guide leakage into the valve covers and onward to the breather? The pressure can come from some source(s) including the front crankshaft oil seal mentioned.

I know for some air cooled motorcycle engines that fail to break-in properly and have a good piston ring seal it's common to have excessive crankcase oil and fumes directed into the intake where they are plumbed.

Correlation isn't necessarily causation as some scientists like to say.

Gary

[Ragwing nut]

Is there a correlation between leak down cylinder tests and elevated crankcase pressure? How about exhaust valve guide leakage into the valve covers and onward to the breather? The pressure can come from some source(s) including the front crankshaft oil seal mentioned.

I know for some air cooled motorcycle engines that fail to break-in properly and have a good piston ring seal it's common to have excessive crankcase oil and fumes directed into the intake where they are plumbed.

Correlation isn't necessarily causation as some scientists like to say.

Gary

piston ring blow by will give a higher case pressure if its bad enough.

[N96337]

One of the most common things I've found is a dip in the breather line. That's caused a lot of messes. I did have one engine that they said was puffing smoke after a few hours of running. I knew it wasn't on the test cell, so I went to investigate. They had the breather outlet facing forward...... go figure.
John

[astjp2]

One of the most common things I've found is a dip in the breather line. That's caused a lot of messes. I did have one engine that they said was puffing smoke after a few hours of running. I knew it wasn't on the test cell, so I went to investigate. They had the breather outlet facing forward...... go figure.
John

My Taylorcraft breather goes out the bottom, I dont go over the top like some do.

[PA1195]

Blowby? May be >

Poor break-in and/or piston ring seal throughout stroke
Exhaust valves to guides loose
Flat prop so low BMEP load on pistons and rings
Too low cruise rpm and manifold pressure
Too much sump oil
High oil temps
Breather outlet in low air pressure zone
That front crank oil seal air leak
Oil that turns dark quick is an indicator for some of the above

Gary