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160 H.P. Conversion

S

Stealthchicken

Registered User
Friendswood, TX
I'm in the early stages of rebuilding my Supercub. I'm sure that over the next few months I'll be posting a lot of inane questions, and here's my first:

I understand that converting the low-compression 150 h.p. O-320 to the 160 h.p. flavor is simply a matter of changing the cylinder assemblies. Presumably if I purchase the high-compression (B-series) assemblies from, say, ECI and bolt them on as part of the overhaul I'll then have an O-320 B2B. What exactly is the approved data that you all use when filling out the 337 to justify this conversion? I've found the SI that covers the change to the data plate (SI-1304J) following the conversion, by the way.

If anyone has an approved 337 to share I'd really appreciate having a copy.

Also, who has the best STC for installing the engine back onto the airframe?

Denton.
 
First, you must have a wide Deck engine.
then there are several options.
1. buy STC to just change pistons and pins (& older style ex valves)
2. Convert to B2B by changing (or having yours modified) Cyls, pistons and pins.

But the Key is you must have a wide deck engine. unless you want to get real expensive modifying a narrow deck.

Don't have the SB's in front of me right now to give you the other info.
Brian
 
Yep, I got the wide deck, so no problem there. I intend to do the conversion during the overhaul, so I'll just replace the entire cylinder assembly with the high-compression model. My question: How do I justify this on the 337?

I understand that Crosswind STOL also has an STC to install the 160 h.p. on the airframe. Is there any compelling reason to prefer CC over Crosswind, or vice versa?

Denton.
 
Here's one for the legal eagles: Suppose an FAA repair shop does the conversion. Does that mean that form 337s are not required? Next, suppose it was done in Canada, a place where we have a treaty recognizing each others' work on airplanes. Do you need an STC? Legal in Canada = legal in the US?
 
If you have a wide deck, why change the cylinder assemblies? All you need to do is install an 8.5:1 piston.
 
All wide deck engine suffixes end in A --- For example, an O-320-E2A is a wide deck 150 hp and an O-320-D2A is a wide deck 160 hp. The B3B suffix does not end in A.

As an aside, some E series engines have an O-235 front main bearing and those are not supposed to be converted to 160 hp, though there is at least one STC to do so. That said, I don't see why the O-235 front main should limit the output, because the O-340 also used that bearing and they put out more than 160 hp.
 
P.S. I'm aware that some 150's have plain steel cylinders and 160's are nitrided. But, I don't believe there is a requirement that all 160 cylinders be nitrided.
 
JimC said:
All wide deck engine suffixes end in A --- For example, an O-320-E2A is a wide deck 150 hp and an O-320-D2A is a wide deck 160 hp. The B3B suffix does not end in A.

.
Click to expand...

Jim -- that's not right. All wide deck engines serial numbers end in A (XXXXX-27A)


As far as converting to 160 without changing cyls. The low compression cyls have have straight wall and the high compression cyls have choked walls. So legally you can't do it that way without using the STC.
 
Re: 160 conv

leon tallman said:
so the 0 320B3B is that a wide deck
Click to expand...

Look at the S/N if it has an A at the end it is. Not familiar wtih the B3B , but lycoming made a lot of engines in both narrow and wide deck.
O-320-A2B and O-320-B2B could be either.
 
You're right -- I mispoke about the engine suffix -- it is the engine serial # that ends in A for the wide decks. For example, the B3B comes in both narrow and wide decks. Wish I had said more so I could take that back too :)

Re the cylinder choke, there are STC's that allow you to convert an unchoked cylinder to 160 hp. For example, Art Mattson's STC to convert an O-320-E2A to 160 hp (I fly a 160 hp Cherokee 150C that uses that STC). So legally, you CAN do it with an unchoked cylinder, but it does require an STC (which does exist).
 
160hp

Charly Center(Crosswind)never finished the float approval for his 160hp STC.
Cub Crafters did.
 
Nanook, thanks for that info. CC's is where I'll get my STC.

I know I can get an STC for putting high-compression pistons in straight wall cylinders. Ly-Con sells such an STC, I believe. But I don't want to go down that road. The engine is going to be overhauled anyway, with new cylinder assemblies, so I might as well go with choked cylinders as the 160 h.p. came from the factory. There is no STC for this, so far as I know, so I have to reference factory drawings, overhaul manual, etc., on the 337. What has everyone else used for acceptable data?

Denton.
 
I would use the Lycoming manuals as data but there is an STC held by an engine shop in AK. I can lok it up when I get to the hanger.
 
I have used the Lycoming manuals for references and have been given field approvals.

John
 
160hp

Aero Recip. bought Pacific Ak. or was it Seattle/Pacifics? STC for installing the higher comp. pistons and heavy pins. You rivet their data plate next to lycomings' when you get done
 
I've done a few conversions, with just a 337. no need for a field approval unless you aren't converting it exactly like a B2B.---T.J. says you don't even need a 337, but I digress there.
Somewhere in the gobbldygoook of FAR's and SB's it tells you how.
Just have to reference all the applicable SB's and Service letters adn probably FAR's.
Like my friendly FAA rep told me one time, " I know how to do it, when you figure it out, let me know and I'll tell you if you are right" :bad-words: And I did !!! $#%&*
.
Remember, the Lycoming Parts Manual is not an FAA approved document unlike the SB's and if you use that , you probably do need a field approval.
 
So the Question I have is, If you are gonna use a O-320 for an upgrade which one should I look for,A2b, E2d Wide deck, Narrow deck etc? I checked a lot of past info on this site but no one seems to have a set in stone idea which model #motor to use? Thanks,Tom
 
engine model

Tom If you want 160hp then you need a narrow or wide deck 0320 B2B or if your going to convert a 150 hp 0320 you want a wide deck 0320 A2B that you will convert to a B2B Some others will work also like a B3B which is a 0320 160 hp with slick mags from the factory I think.
Dave
 
Here's a rhetorical question: what if your airplane has a 150 hp engine and you simply want to add 10 hp---is that going to be an issue with getting an approval? Example: I have the McKenzie O-320 STC for my PA-12 (which incidentally doesn't mention the horsepower / engine series anywhere that I can find). If I want to convert it to 160 hp, is the FAA going to allow that in my airframe without an airframe STC/engineering data for the add'l horsepower? Seems like you could open up a whole can of worms, especially if your existing STC specifically states the engine /airframe combo is approved for 150 hp.

Very curious, thanks.

Andrew
 
The FAA Field Inspectors Handbook allows a 10% hp increase via field approval. Now, if you can find a field inspector to approve it is another question. :cry:
 
I have the McKenzie STC for my PA-12, too, and am running an O-320-B3B (160 hp). I can send you copies of the 337s if you need them.

Eric
 
I talked with the guys at aircraft specialties and they said there are only choked barrels made anymore. strait barrels haven't been manufactured in years. I checked my O-320 150 that had 15 year old cyls and checked the ring end gap at the bottom of the cylinder and top (by pushing the ring in the cylinder with the piston) and noted difference. I looked online to get tips on checking ring gap and this is the method I found.
The pistons are another factor, part # 75413 is the 150hp 7:1 ratio and 75089 are 160hp 8.5:1 ratio, I think this is where the hp difference is. Ideas?
 
Ok thanks, I did hear about the heavier wrist pins being part of the STC, I guess what I was wondering is the only physical differance the higher compression pistons and wrist pins? Same cylinders if wide deck engine is being used?
 
Lycon offers an O-320 lycoming 150-160 STC for wide decks... Pretty sure the Pistons and wrist pins are the only difference..


Sent from my iPad using Tapatalk
 
Last edited:
Mark_Moyle said:
Lycon offers an O-320 lycoming 150-160 STC for wide decks...
Click to expand...
An STC is not necessary. Both are approved on the same TC you only need to compare part numbers in the Lycoming parts manual.
You may need an STC to install the modified engine in the airplane but not to modify the engine.
 
Skywagon is right no need for a 337 just build it up as a b2b using all the part #s from the parts manual. 95% of the parts are common. Use the sb to change the data tag, you do need the stc from cub crafters for the 160hp on the airframe.
 
I've been looking into this myself for my plane, and while searching this site I found this thread.

Darrel sums it up nicely and wraps it with a bowtie in post #5

I'm not a member, an the site won't allow me to post URL's, so search

160 HP Paperwork problem - help!
 
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