Avstar Aircraft of Washington, Inc.

10415 172nd St. E., Hangar A1
Puyallup, WA  98374
office (253)770-9964
or (253)770-0120
email:  avstarair@att.net

11-01-1999 Ask Mike! Archive
What do these engine configuration numbers mean?

Dear Mike
I recently bought an engine and I'm confused about the configuration numbers.  Say you have a IO 320 A1A does this engine come with several different types of case configurations i.e. dynafocal 1 dynafocal 2 or did Lycoming just build this one way.  I thought that the numbers were there to keep the different configurations from being confused.  Or am I wrong?  Are there 3 or 4 different types of IO 320 A1A?

Lycoming has done some interesting things with their manufacturing methods corresponding to part numbers and model numbers. (The biggest place the confusion comes from is actually in the cylinder flange configuration.) Unless the subject engine has been field modified, your question concerning engine mount configuration can be answered as follows.
I trust the engine you purchased is the IO-320-A1A, because this answer can only be applied to this specific model. I'll also trust you purchased this engine for a homebuilt, and now you need to buy / build the mount to attach to your airframe. According to Type Certificate Data Sheet 1E12-7, which is the "public record" portion of the FAA approval for Lycoming to build this engine, the IO-320-A1A uses a Type 2 Dynafocal mount (18 degree), as opposed to a Type 1 (30 degree) or Conical (straight).
This is found working backwards in note 7.
Hopefully, you received the log book(s) for this engine; if it was previously on a certificated aircraft, the above information should be accurate; however, I have seen some "back yard overhauls" for engines used in experimentals that were a piece-meal of parts, and identification can be trying, at best. A visual inspection will confirm what you have for mounting. If the four bolt holes are parallel to the crankshaft, this is a conical mount. If they intercept the crankshaft by 18 degrees, it is a type 2 dynafocal; by 30, it's a type 1 dynafocal.
Hopefully this helps.
Gear Green,

Dear Mike
Thank you very much for steering me in the right direction. Yes I am building an experimental. The kit plane manufacturer I am dealing with is working on a option to upgrade from IO 240 Continental to IO 320 Lycoming. This all started when I called them to ask for engine type. They told me IO 320 A1A, so after 6 weeks of searching I found a guy in L.A. who had one still in a plane still running 300 SMOH. So I flew to L.A., flew the plane, engine ran good, great in fact. While I was there I talked to an A&P about the engine, he told me it was dynafocal 2 and that most IO series were like that. Called the kit builder when I got back asked again about the engine mount they were building, they told me it was dynafocal 1. That's how the trouble began, they had taken a O 320 converted it to fuel injection put a A1A configuration to it and told all the guys that are building these that this was a readily available engine. They then told me that they really had no plans of welding up a type 2 mount. I called Lycoming, they told me this engine only came this one way but up until now I had no backup that I could send the kit builder and all the guys to prove that they had a oddball engine and that the kit builders were really screwing up guys like me who would like to have a CERTIFIED engine for their plane. Got a email back from a guy the other day who has a motor like this all yellow tagged 0 time 12k but has dynafocal 2 of course, great deal. So I copied the file you sent me to, sent it to the kit builder and all the guys building this plane. The kit builder had told everybody that they had a guy who could build an engine just like the one they have for about 17k I paid 8500, yes I did buy the engine after all. So now at least I have made my point with these guys hopefully they will reconsider their position on the engine, and just weld a type 2 ring on the mount and be done with it. Sorry to ramble on, thought you might like to know what you were doing the research for. Us home builders need all the help we can get THANKS.