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O-320 Crank

Grant

Grant

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At Work.....
Now, I've "Heard" that the early O-320 narrow deck cranks are a fair bit lighter than the later cranks but they are the same part number and can be interchanged. Since I need a new crank for my engine (Mine's bent), I'm wondering two things:

1: Is this a myth or is it true that I can reduce my rotating weight if I were to find a narrow deck crank?
2: If so, What are the chance I'd ever find a good narrow deck crank?
 
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Grant, I can't vouch for the part numbers, I believe you'll find the differences are in the propeller flange. Thickness and holes or not. I found several of the webs between the holes on one cracked during an annual. There wasn't much keeping the prop on the engine. This was not from a prop strike as it was on a PA-22.

There are some places where you don't try to save weight.
 
Those light flanged cranks bend way easier than the heavy flange. I have run them for years without issue but would pay less for a light flange vs a heavy flange.
 
I'm looking for ways to reduce the rotating engine mass. There are a few additional ways that are approved that I'll be doing if I can find the parts. They are all original Lycoming parts. Lighter wristpins, lighter connecting rods. I also heard there was an STC to help keep the cam lubed during extremely low RPM (Seaplane Idle), Whereby the cam is drilled with oil galleys for each lobe.

I have this thing apart and looking at several options to make it a little snappier....

Thanks Fellas!
 
Steve Pierce said:
My personal experience is just in case of a prop strike the flange is easier to bend.
Click to expand...
That could be the reason they didn't make a big deal out of prop strikes in the "old" days. The flange bent and that was it. If it was within certain limitations it could be straightened without even dismantling the engine.
 
PA-22/20-160 said:
Anyone have evidence that the light flange cranks fail more often then the heavier ones? Or is it just a gut feeling.
Click to expand...

Compare numbers of O-320 bent cranks with how many O-360's you hear of getting bent cranks. Lighter/smaller is just easier to bend.
 
Grant , not certain if this core engine would help you ( someone on this site can answer this ) but I have a o-320E2B complete engine with logs. 1701.4 hrs - first run and never been apart if I remember correctly . Possibly crank the same ?
 
Also to 60Cub and Grant, the crank in that E2B should be the same as the A2A or A2B. To use it in a no suffix or A1A, I think you would only need to change the flange bushings.
 
Firewall Forward in Ft. Collins, CO has an STC to drill the camshaft for oil flows. I just did it on my 0-360 Overhaul.
Jerry at 1-800-444-0556
 
Cam

sindelir said:
Firewall Forward in Ft. Collins, CO has an STC to drill the camshaft for oil flows. I just did it on my 0-360 Overhaul.
Jerry at 1-800-444-0556
Click to expand...


Any information on how - were the oil holes are drilled.
sounds like a great mod to help cam - followers life .
 
A few things to consider as well...
The early cranks have sludge tubes and are not always interchangeable. I would avoid sludge tube cranks.

Changing the rotating mass of a 320 engine with a fixed pitch prop will never be noticed in the cockpit...you will never see a difference. Flying Reno at 3200RPM..maybe.
It can be made smoother with a good dynamic balance which should INCLUDE the ring gear support.
Many people think a dynamically balance crank is a good thing and it is but only if it is balanced WITH the ring gear support on a Lycoming engine. This you can feel.

Splash lubrication on the 320 cam is pretty good at idle. Its the startup that kills it. Holes in the cam don't help unless you have a pre-lube pump to pressurize it before start.
 
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Grant said:
Now, I've "Heard" that the early O-320 narrow deck cranks are a fair bit lighter than the later cranks but they are the same part number and can be interchanged. Since I need a new crank for my engine (Mine's bent), I'm wondering two things:

1: Is this a myth or is it true that I can reduce my rotating weight if I were to find a narrow deck crank?
2: If so, What are the chance I'd ever find a good narrow deck crank?
Click to expand...


True and I have one ready to go!

6F36C257-0ED5-4E21-ACAF-0BB4542C0457.jpgBFEEB17C-0AD0-44CC-A762-1304DABD44DB.jpegA04A8301-2F24-4318-83D7-624031E144DB.jpgF18D0BEC-3C73-4BF1-B310-187B5CB55548.jpg36B318FD-B4A4-490B-93A2-671296BC2C4E.jpg

I also have a set of yellow Tagged conncying rods all done bu Custom Aircraft in Palmer. PM me for details.
 

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