O-320-A2B Cylinder Deck Thickness

[Robert M]

I recently got me a Lycoming O-320-A2B. I've pulled it apart for inspection and overhaul. The serial number indicates that it is a narrow deck engine, it has the barrel type, internal spline nuts but it did not have any cylinder plates.

I understand that the ND's can be modified to accept WD cylinders (at a considerable cost). So, what is the thickness of the deck of either? I'd just like to check mine to be sure either way.

Thanks,

[mahlon_r]

N/D cases can't be modified to W/D. The plates go with high compression N/D cylinders the low compression engines don't get plates but a different spot faced cylinder where the barrel nuts go.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[Robert M]

Originally Posted by mahlon_r

N/D cases can't be modified to W/D. The plates go with high compression N/D cylinders the low compression engines don't get plates but a different spot faced cylinder where the barrel nuts go.
Good Luck,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

Thanks! What is meant by "spot faced" cylinder?

[mahlon_r]

The cylinder that doesn't use the plates, has a spot face machined into the flange where the barrel nut goes. The cylinder that uses the plates, doesn't have this machined area. That is an easy way to tell the cylinders apart.
The crankcase that uses the spot faced cylinders has shorter cylinder mounting studs then the one that uses the plates.
Good Luck,
Mahlon

?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

[Robert M]

Originally Posted by mahlon_r

The cylinder that doesn't use the plates, has a spot face machined into the flange where the barrel nut goes. The cylinder that uses the plates, doesn't have this machined area. That is an easy way to tell the cylinders apart.
The crankcase that uses the spot faced cylinders has shorter cylinder mounting studs then the one that uses the plates.
Good Luck,
Mahlon

?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

Awesome information, thanks! Now I've got to go home and check my cylinder decks.

[Robert M]

Mahlon.

Here are some pix of my number 4 cylinder base deck stud holes. If I understand what you were telling me, these do have the spot face design and the base plates are not needed.