O-360-A1D question for true parts geeks

[DXB]

Are the Lycoming O-360-A1D wide deck engine cases on early M20Cs (specifically '65 and '68) interchangeable?   

I am trying to source a case unexpectedly in the middle of my overhaul.  The engine S/Ns in question are L-9102-36A and L-11216-36A.

I called Lycoming  - they said they had to dig into microfiche records (!) to check, and they haven't gotten back to me. 

As a member of gen X, I suspect I am among the last humans born to have a clue what microfiche is 

[jetdriven]

Wide deck didn’t come out until about 1975-1976. Yours is a wide deck engine that IIRC matches the original S/N but that had to be a narrow deck engine originally.  But none of the two overhaul records really mention swapping the case for a wide deck.  But there’s one on it. 

[DXB]

13 minutes ago, jetdriven said:

Wide deck didn’t come out until about 1975-1976. Yours is a wide deck engine that IIRC matches the original S/N but that had to be a narrow deck engine originally.  But none of the two overhaul records really mention swapping the case for a wide deck.  But there’s one on it. 

I thought an A at the end of S/N meant wide deck - the case I'm looking at is from a '65 and has a wide deck.

[M20F]

What I can tell you when buying cases is there is a plug for constant speed and without it is fixed (helicopter).  I got the tshirt on that one….

[Igor_U]

3 hours ago, jetdriven said:

Wide deck didn’t come out until about 1975-1976. 

Byron,

Is this specifically for O-360? My 1967 F model came with wide deck IO-360 from the factory in my understanding is that sometime in 1965/66 was the they switched. 

[Pinecone]

From another forum - 

"

"Lycoming engines manufactured before 1964 (1971 for 540 series and 1975 for 720 series) were of narrow deck design. These engines used cylinder base hold down plates and internal-wrenching type cylinder base nuts. After these dates, Lycoming engines became "wide deck", Wide deck engines have regular hex type cylinder base nuts and a thicker cylinder base flange (approximately 3/8" thick). The thicker cylinder base flange makes the wide deck engines slightly wider than the narrow deck engine. The switch from narrow deck to wide deck did not change the model number of the engine even though cylinders and crankcases are not interchangeable. Another method you can use to distinguish narrow deck from wide deck is by the engine serial number. If the serial number ends with the letter "A" it is wide deck-; e.g. L-82374-27A."

This is from the "Sky Ranch Engineering Manual" by John Schwaner on the operation, failure and repair of piston aircraft engines. This is a very good book and is available at http://www.sacskyranch.com/ or in Trade-A-Plane."

The same post references info from Lycon that the wide deck are more prone to cracking.

[DXB]

Based on prehistoric cave paintings at Lycoming, it's the correct case!!

My old one is getting fully rehabbed at DIVCO and be on the market at some point with an 8130 early next year.... 

[jetdriven]

18 hours ago, Igor_U said:

Byron,

Is this specifically for O-360? My 1967 F model came with wide deck IO-360 from the factory in my understanding is that sometime in 1965/66 was the they switched. 

I’m still learning about this. It seems the twin Comanche was the first thing to get wide deck engines in 1963 or 64. And then it came from there.