Wide, or narrow?

[Mcstealth]

Please tell me how to know the difference between a wide deck or narrow deck engine?

Yes I know "search" is your friend,  but I like asking the group better.

Thanks in advance. 

Edited October 12, 2023 by Mcstealth

[Andy95W]

The easiest way to tell is by looking at the fasteners that hold the cylinders on. Wide deck cylinders use “normal” looking nuts, narrow deck engines use nuts that are round on the outside and have teeth on the inside.

[M20F]

The main difference is wide deck cylinders cost 4x’s as much. 

[philiplane]

Narrow deck cases don't suffer from the amount of cracks that wide decks do, which is odd, since the wide deck case was supposed to be better.

 

[Mcstealth]

20 hours ago, Andy95W said:

The easiest way to tell is by looking at the fasteners that hold the cylinders on. Wide deck cylinders use “normal” looking nuts, narrow deck engines use nuts that are round on the outside and have teeth on the inside.

The plane in question is too far away for a visual inspection unfortunately. 

Any numerical way?

[EricJ]

44 minutes ago, Mcstealth said:

The plane in question is too far away for a visual inspection unfortunately. 

Any numerical way?

There's some general wisdom that says that if the serial number ends in 'A' it is a wide deck.  

Edit:  I found a reference!   Lycoming SI1037W says:

Engine models that have serial number suffix “A” or “E” are built with crankcase configurations for wide cylinder base mounting flanges, and consequently must be assembled with “wide deck” cylinders.

Engines with no serial number suffix require “narrow deck” cylinders. Refer to the latest revision of Lycoming Service Letter 220 for additional information on differences between Narrow Deck and Wide Deck Engines.

[GeeBee]

In addition to the difference in fasteners, narrow decks have hold down plates around the cylinders. Internally the engines are pretty much identical, but the cases and cylinders are different. The reason for the change is Lycoming wanted to standardize cylinder production, and going to the wide deck design allowed them to do that. Here is a picture of the plates.

https://www.texasairsalvage.com/main_view.php?editid1=223622