Continental Aircraft Engine FAQ

What is the difference between parallel head and angle head

Both Lycoming and Continental engines use a parallel and angle head design on their cylinders.
For example, the early IO-470 engines were of parallel head design and later models used a angle head design. Lycoming 540 engines can be parallel head or angle head. Especially, when ordering rocker cover gaskets we may ask whether you have a "parallel head" or "angle head".

Angle head have the valves entering the combustion chamber at an angle and therefore use two rocker shafts. Parallel head cylinders have the valves entering the combustion chamber parallel to one another and therefore use one rocker shaft.

Here's an example of both:

Continental O-200 parallel head cylinder

Continental O470 angle head engine

For those who have to ask which is better: Angle head - read my Sky Ranch Engineering Manual to find out why - shameless plug!