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Lycoming engine designations and dimensions

Saville

Saville

Well Known Member
Hi all,

I'm trying to understand the Lycoming engine designations as well as obtain their dimensions. I'm on the Lycoming page. Part of the nomenclature I understand; part I do not.

So you have:

Prefix-displacement Configuration

Prefixes are well defined on the Lycoming page: O, IO, AE etc. so I understand those.

Displacement - no problem.

Configuration?

I don't see any clear definition of those but have been able to figure some out (I think).

A1A for example.

From what I can tell, the "1" means that the engine is rigged for C/S prop. A "2" generally seems to mean not rigged for C/S prop.

Is that correct?

However it doesn't seem to be the case that the letters on either side of the number means anything. You have to look at the descriptions like:

"Same as A3A except for straight riser in oil sump and -32 carburettor "

to know how that model is configured. Is that also correct?

Lastly, how does one find out if one particulare engine can be placed on the same mount as another? The configuration descriptions will tell you things like:

O-320-A2D - Same as E3D but with conical mounts.

But how does one find out if an O-360 rigged for conical mounts can be bolted to yoru engine mount where an O-320-A2D was previously hung?

the A2D doesn't sem to mean the same things across different engines. For example:

O-320-A2D - Same as E3D but with conical mounts.
O-360-A2D - Same as the A1D except that it has no provisions for a controllable pitch propeller.
O-320-B2D - Same as D1D but with conical engine mounts ...

Can I replace the O-320-A2D with a O-320-B2D?

Is there any place I can get a listing of the dimensions of the mounting points of the engines so that I can determine if a mount for one engine works with another?

Thanks
 
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You may be overthinking this. The O-320 and O-360 are very similar in overall exterior physical dimensions. The various suffix codes refer to configuration changes from another configuration. The motor mounts are either Conical, dynafocal I or II. This means that an conical O-360 engine would bolt up to a mount that previously had a conical 0-320 motor hung on it no problem. This is my understanding anyway.

There is a rumor circulating that Lycoming built at least two engines in the same configuration but, to my knowledge, this has never been proven. :)


Bevan
 
It's as clear as mud

Saville said:
Hi all,

I'm trying to understand the Lycoming engine designations as well as obtain their dimensions. I'm on the Lycoming page. Part of the nomenclature I understand; part I do not.

So you have:

Prefix-displacement Configuration

Prefixes are well defined on the Lycoming page: O, IO, AE etc. so I understand those.

Displacement - no problem.

Configuration?

I don't see any clear definition of those but have been able to figure some out (I think).

A1A for example.

From what I can tell, the "1" means that the engine is rigged for C/S prop. A "2" generally seems to mean not rigged for C/S prop.

Is that correct?

However it doesn't seem to be the case that the letters on either side of the number means anything. You have to look at the descriptions like:

"Same as A3A except for straight riser in oil sump and -32 carburettor "

to know how that model is configured. Is that also correct?

Lastly, how does one find out if one particulare engine can be placed on the same mount as another? The configuration descriptions will tell you things like:

O-320-A2D - Same as E3D but with conical mounts.

But how does one find out if an O-360 rigged for conical mounts can be bolted to yoru engine mount where an O-320-A2D was previously hung?

the A2D doesn't sem to mean the same things across different engines. For example:

O-320-A2D - Same as E3D but with conical mounts.
O-360-A2D - Same as the A1D except that it has no provisions for a controllable pitch propeller.
O-320-B2D - Same as D1D but with conical engine mounts ...

Can I replace the O-320-A2D with a O-320-B2D?

Is there any place I can get a listing of the dimensions of the mounting points of the engines so that I can determine if a mount for one engine works with another?

Thanks
Click to expand...

According to page 2 of SSP 108 the first digit of the suffix denotes a change [from the original design] of the power section and/or horsepower rating. An example would be conical or Dynafocal mounts. This changes the design of the crankcase halves [at the rear]
The second digit of the suffix denotes a change in the nose section of the engine. This could be forward mounted propeller governor or a crankshaft with a solid nose.
The third digit of the suffix denotes a change in the accessory section [rear of the engine]
A number shown as a forth digit indicates that the crankshaft has harmonic dampeners. The number tells the order of vibration that these dampener are designed to "dampen" or tune out.
The letter D as the fourth [engines without dampeners] or fifth [engines with dampeners] digit indicates that the engine has a dual [2 in 1] magneto.
Refer to SSP 108 for exactly how any variant differs from the base model engine.
Charlie
PS In the past, it was easy to find SSP 108 online. A quick Google search came up empty. If anyone wants a copy, contact me via email or PM.
 
Engines

SSP 108 does a very poor job on engine mount configuration.
Starting with the 0 320A, the A's are generally low compression engines, the B's are high compression.
 
Engines

One other issue-there is no relationship between the O and IO engines on the SSP 108 document. O 320 B and IO 320 B are both high compression engines, other factors may be different.
108 also does not designate whether wide or narrow deck. The serial number must be used for that. There is a number stamped on the top of the crankcase near the rear. If this is followed by and A, its wide deck, no letter narrow deck. Of course if you are looking at an assembled engine there are other visual clues.
The narrow deck engines are mostly pre 1964. Some parts such as new crankcase have not been available for a long time. For that reason I would avoid the narrow deck.
Likewise, avoid some of the E models and certainly the H models.
 
More info and a question

jrs14855 said:
SSP 108 does a very poor job on engine mount configuration.
Starting with the 0 320A, the A's are generally low compression engines, the B's are high compression.
Click to expand...

The C's & E's are also low compression. The D series is high [8.5 to 1] compression. These rules are ONLY for O-320s. IO-320s & 360s differ. Can you recommend another Lycoming tech document that better illustrates which models are conical mount and which are Dynafocal?

Charlie
 
Bevan said:
The O-320 and O-360 are very similar in overall exterior physical dimensions.

Very similar? Or the same? I want to know if I can bolt an O-360 Conical where an O-320 Conical sat. Or a 360 dynafocal 1 replacing a 320 dynafocal 1. etc.


The motor mounts are either Conical, dynafocal I or II. This means that an conical O-360 engine would bolt up to a mount that previously had a conical 0-320 motor hung on it no problem. This is my understanding anyway.


Bevan
Click to expand...

Is this everyone's understanding?

thanks!
 
Saville said:
Hi Peter,

Thanks but I already had all that information. Unless I missed something, he document doesn't tell me if I can bolt an O-360 Dynafocal II onto an engine mount where an O-320 DII now hangs.

thanks
Click to expand...

Yes, you can install an O-360 Dynafocal II engine on a Dynafocal II mount which originally had a Dynafocal II O-320. Question, do you already own this mount and engine? Or are you asking to help understand your options when choosing an engine?
Regarding the engine mounts, a Conical mount will work with any 235, 290, 320, 340 or 360 cubic inch engine with provisions for Conical mounts. The same holds true for the Dynafocal I mounts and the engines designed for them.
Regarding the Dynafocal II mounts, they were designed for aircraft with wing mounted twin engines. They have a 30 degree focal point, as opposed to the 18 degree focal point used on the Dynafocal I mounts, which are designed for single engine aircraft. If you do find a great deal on a used Dynafocal II engine, be aware that it can be converted to Dynafocal I, by Divco. The engine needs to be disassembled and the crankcases sent to Divco for this to be done. It's only cost effective if you were planning on having your crankcases overhauled. Divco's web site is linked below.

http://www.divcoinc.com/


Charlie
 
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chaskuss said:
Yes, you can install an O-360 Dynafocal II engine on a Dynafocal II mount which originally had a Dynafocal II O-320. Question, do you already own this mount and engine? Or are you asking to help understand your options when choosing an engine?
Charlie
Click to expand...

I'm asking this question to help understand my options when I buy an already-built RV-4.

Each -4 for sale has it's own engine/mount configuration. I may want to upgrade an O-320 to an O-360 in the future. I want to be able to look at a prospective a/c and know whether or not I can do the upgrade without modifying the mount and/or firewall.

thanks
 
Saville said:
I'm asking this question to help understand my options when I buy an already-built RV-4.

Each -4 for sale has it's own engine/mount configuration. I may want to upgrade an O-320 to an O-360 in the future. I want to be able to look at a prospective a/c and know whether or not I can do the upgrade without modifying the mount and/or firewall.

thanks
Click to expand...

Yes, the engine mount will not be an issue, assuming that you replace a conical 320 with a conical 360 or a Dynafocal I 320 with a Dynafocal I 360. That being said, the 360 is 1" wider than the 320 [cylinder assemblies are 1/2" longer to deal with the 1/2" longer stroke of the 360] Make sure you have room inside the cowl to install the 360 without rubbing. Van never intended the 360 to be installed on the 4, when he designed it. It's not an uncommon upgrade. I would suggest that you contact someone with an O-360 or IO-360 RV4 to find out if you will need to modify [widen] the cowl. That could prove to be a rather labor intensive mod. The RV3 & RV4 cowls are so tight, that even installing the larger 60 - 90 amp ND alternator requires mods to the cowl. Vans sold both 320 & a wider 360 cowl for the RV6/6A.
Charlie
PS Very carefully inspect the lower, outer corners of the firewall on any RV 4 you consider purchasing. Also look on the back side of the firewall at the lower corners, for adding the reinforcing gussets that Vans issued a update in the RVator [going from memory here] for to prevent buckling of the lower, outer corners of the firewall. You can purchase the lower longeron to firewall gussets for an RV8 from Vans and install them, if you prefer not to fabricate them, per the RVator article.
Vans has discontinued the Dynafocal II engine mount per Service Letter. See

https://www.vansaircraft.com/pdf/Dynafocal_II.pdf

So if you buy a RV with a Dynafocal II engine and the mount cracks or you damage it in a ground loop incident, you can not buy a new one from Vans
Charlie
 
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There are not nearly as many O-360 configurations for Conical mount as O-320. Piper used the Conical mounts, as did American Champion. Those are mostly O-320's. Currently, Robinson Helicopter still uses them for the 4 cylinder R22's. The O-360C is conical.

If you are looking for a power upgrade with minimal work at overhaul, you might consider an IO-340 stroker conversion to your current O-320. With 9.5:1 pistons and an electronic ignition setup, you could be looking at the 185HP range with minimal baffling work and the same mount.

This is essentially a crankshaft and connecting rod change marketed by ECi.
 
Engines

chaskuss said:
Yes, you can install an O-360 Dynafocal II engine on a Dynafocal II mount which originally had a Dynafocal II O-320. Question, do you already own this mount and engine? Or are you asking to help understand your options when choosing an engine?
Regarding the engine mounts, a Conical mount will work with any 235, 290, 320, 340 or 360 cubic inch engine with provisions for Conical mounts. The same holds true for the Dynafocal I mounts and the engines designed for them.
Regarding the Dynafocal II mounts, they were designed for aircraft with wing mounted twin engines. They have a 30 degree focal point, as opposed to the 18 degree focal point used on the Dynafocal I mounts, which are designed for single engine aircraft. If you do find a great deal on a used Dynafocal II engine, be aware that it can be converted to Dynafocal I, by Divco. The engine needs to be disassembled and the crankcases sent to Divco for this to be done. It's only cost effective if you were planning on having your crankcases overhauled. Divco's web site is linked below.

http://www.divcoinc.com/


Charlie
Click to expand...
The type II dynafocal was not designed for twin engine or wing mounted engines. It was designed for the Piper PA30 Twin Commanche which has a long prop extension built in to the hub of the special Hartzell prop. The type II was designed to counter the extra moment arm of the prop.
 
jrs14855 said:
The type II dynafocal was not designed for twin engine or wing mounted engines. It was designed for the Piper PA30 Twin Commanche which has a long prop extension built in to the hub of the special Hartzell prop. The type II was designed to counter the extra moment arm of the prop.
Click to expand...

Jim,
I could not remember the exact make & model aircraft that the Dynafocal II was created for. I knew that it was a twin, with wing mounted engines [not a Sky Master or similar] As you stated, the 30 degree focal point was to compensate for extended prop. Thanks for giving us the exact use of that mount.
Charlie
 
Mount

chaskuss said:
Jim,
I could not remember the exact make & model aircraft that the Dynafocal II was created for. I knew that it was a twin, with wing mounted engines [not a Sky Master or similar] As you stated, the 30 degree focal point was to compensate for extended prop. Thanks for giving us the exact use of that mount.
Charlie
Click to expand...

The angles previously posted are reversed. The very common Type I is 30 degrees. The relatively rare Type II, 18 degrees, was used mostly on the Twin Commanche, also the Wing Derringer, only 10 built???, and an Aerostar. I have never seen a four cylinder Aerostar but the list shows it. They also list some aircraft I never heard of, probably foreign.
Piper singles from about 63-64 on used the type I dynafocal, except for maybe a few Super Cubs.
Cessna used the 0 320D (dynafocal I) on some 172's prior to suspension of production in early 80's.
 
Doh! My bad.

jrs14855 said:
The angles previously posted are reversed. The very common Type I is 30 degrees. The relatively rare Type II, 18 degrees, was used mostly on the Twin Commanche, also the Wing Derringer, only 10 built???, and an Aerostar. I have never seen a four cylinder Aerostar but the list shows it. They also list some aircraft I never heard of, probably foreign.
Piper singles from about 63-64 on used the type I dynafocal, except for maybe a few Super Cubs.
Cessna used the 0 320D (dynafocal I) on some 172's prior to suspension of production in early 80's.
Click to expand...

Thank you for correcting me. As the old joke goes, of all the things I've lost, I miss my mind the most! :) I should know better than to trust my memory. While looking on line to verify your statement, I managed to stumble across two pages on Lycoming's web site which list both the height, width & length of the various engines, and their mounting type as well. See below for 320s

http://www.lycoming.com/Lycoming/PRODUCTS/Engines/Certified/320Series/EngineData.aspx

Look here for 360 engines

http://www.lycoming.com/Lycoming/PRODUCTS/Engines/Certified/320Series/EngineData.aspx

Charlie
 
Engine

chaskuss said:
Thank you for correcting me. As the old joke goes, of all the things I've lost, I miss my mind the most! :) I should know better than to trust my memory. While looking on line to verify your statement, I managed to stumble across two pages on Lycoming's web site which list both the height, width & length of the various engines, and their mounting type as well. See below for 320s

http://www.lycoming.com/Lycoming/PRODUCTS/Engines/Certified/320Series/EngineData.aspx

Look here for 360 engines

http://www.lycoming.com/Lycoming/PRODUCTS/Engines/Certified/320Series/EngineData.aspx

Charlie
Click to expand...

I can't keep all that stuff straight either, I usually have to look it up each time. I do remember the mount angles because I have built a few type I engine mounts. I even built the entire ring assembly for one Pitts.
Have you ever heard of an Aerostar with four cylinder engines?
 
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