Does anyone know if you can install an O470L in a 1976 Cessna 180J? The type certificate shows it came with an O470S or R originally. Only reason to install an O470L is there is one available with very low time on it. Any help would be appreciated.

Can't be done, now who has the low time L. Just kidding

TCDS lists 470R & 470S for a 180J.
The TCDS does list the L or R engine for the 180 C through H models, so you might be able to get a field approval without too much trouble.
Or maybe there's an STC out there for an L engine on a J model 180?

What's the difference(s) between the L and the R & S?
There might be other obstacles than just paperwork.
For example, the A J & K engines are listed for the original 180,
but the K uses a different engine mount arrangement as well as 4 bolt exhaust flanges (instead of 2 bolt).
So installing a K requires that you address these issues.

You need to get in touch with Continental directly, or a really good engine rebuilder with current manuals. You may find that the differences are so subtle, that this L can be converted to an R or S with very little effort.

Not sure of the correct answer to the OP, but am sure that the crank counter weights are different on the L vs an R or S. The 'L' being a Pponk candidate vs the R & S not so...

I seem to recall Iowa Marty converting an L or K to an R or S... or maybe it was the other way around? I also know my IA has done the same. Sound like in this case you were after an easy, economical 'plug and play' so maybe this isn't quite that?

The O-470 TCDS (#E-273) sheds some light on this.

http://rgl.faa.gov/Regulatory_and_Guida ... v%2037.pdf

Bottom line appears to be in Note 5:
"O-470-R is the same as O-470-L except for crankshaft damper configuration".
Note 4 says R has one 5th order & one 6th order damper.
L has four 6th order dampers.
Looks like a different carb dash number also, maybe some other small differences.

Now on to the C180 TCDS:

http://rgl.faa.gov/Regulatory_and_Guida ... Rev_68.pdf

It lists the L & R engines for the C,D,E, & F models.
A number of props are listed, but 2 of them are not eligible for the R engine.
The L & R engines are also listed for the G & H models.
Again, a number of props are listed, but this time 4 of them are not eligible for the L engine.

So it seems to me that the main thing for approval would be making sure your prop is compatible with an L engine.

Thinking about this....even if your prop is not listed for the L engine on the C180 TCDS doesn't necessarily mean you can't use it. The C180 TCDS doesn't list the Mac C201/203 for the K engine installations, but my airplane has an STC from North Sound Aviation approving it.