Peter Clark wrote in
:

On 24 Mar 2008 20:05:49 GMT, Robert Moore
wrote:

Sushidot wrote
..what does the H2AD mean for the Lycomming o-320-h2ad as
well as the "o" in the front of the 320?

320 is the size (cu.in.) of the engine, h2ad indicates model
differences, and "O" indicates that the cylinders are "opposed" rather
than "inline" or "radial" or "Vee".

The "H" engine was one of Lycoming's worst products, bad camshaft
material. Numerous failures early in it's life with the resulant FAA
Airworthiness Directive requiring a special oil additive. Pretty much
a non-issue now since most major oils have this additive as standard.

I've got about 2,000 hours with an "H" engine without a single burp.

Yea, the stuff after the size tells mechanics about engine and
preinstalled accessory oprions (roller tappets, multiple vaccum pumps,
alternators, etc), most of it is pretty esoteric for the guy pushing
the throttle. You can also run into IO- engines, they have fuel
injection instead of carbs.

Good luck on the test!

Lycoming has a list of all their reciprocating engine prefixes & suffixes
in a pdf file on their web pages. You can find it at
http://lycoming.com/support/tips-adv...ints/index.jsp
and then select "Maintenance". The current version has this list on page
28.

This is an excerpt from the information provided by Lycoming.

Format: PREFIX DISPLACEMENT SUFFIX

Prefix:

L = Left-hand Rotation Crankshaft
T = Turbocharged (exhaust gas driven)
I = Fuel Injected
G = Geared (reduction gear)
S = Supercharged (mechanical)
V = Vertical Helicopter
H = Horizontal Helicopter
A = Aerobatic
AE = Aerobatic Engine
O = Opposed Cylinders

Displacement: Cubic inches

Note — A displacement ending in “1” indicates a specific engine model
which incorporates integral accessory drive.

SUFFIX:

A or AA = Power Section & Rating
3 = Nose Section
B = Accessory Section
6 = Counterweight Application
D = Dual Magneto
(Subsequent changes to models are reflected in the suffix.)

--
Marty Shapiro
Silicon Rallye Inc.

(remove SPAMNOT to email me)