O-300 over sized cylinders

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anejohn
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O-300 over sized cylinders

Post by anejohn »

Hi all
General question about over sized cylinders installed on the O-300 Continentals. I had a conversation with a C170 owner who claimed he has over sized cylinders on his aircraft which gives an additional 10-15 horse power. Other forums have had general discussions about this topic and mentioned some Alaska folks have done this for a while. My question is how does the aircraft pass a 100 hour or annual inspection with out “Experimental” stamp on it. Is the mod so discreet that it is easily over looked or is this just hanger talk. If a C170 did have this mod what are the tale tell indications?

Thanks for reading
John
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eskflyer
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Re: O-300 over sized cylinders

Post by eskflyer »

Rethink your ?. Oversize cylinders are used all the time.
High compression pistons are the issue not oversize cylinder's.
No oversize cylinders will not necessarily make more hp. In the o300 you need to make more rpm. Which is what the go300 did to make more hp.
If you exceed the rpm limit's on o300 you risk prop tips going supersonic and cause lots of chaos, depending on your length of propeller.
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Bruce Fenstermacher
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Re: O-300 over sized cylinders

Post by Bruce Fenstermacher »

Unless you mean .015 over standard cylinders, I've never heard of over sized cylinders. .015 over was a way to bore and reuse worn cylinders. You also used a .015 over piston. Never heard anyone claim more horsepower from .015 over cylinders. In fact they could be used mixed with standard cylinders.

Now I have heard of using higher compression pistons in a standard cylinder. Racing engine builders did that back in the day.

How could this be found on an annual? Pistons could be detected with a bore scope but you'd have to know what you are looking at and I'd say many mechanics today wouldn't. I don't recall how thee .015 over cylinders would have been marked.

Yes it can be pretty tuff finding this kind of stuff specially internal engine parts.

Heck unfortunately it can be pretty easy to find a 170 today that has passed 20 annual inspections that doesn't meet the TCDS. I had a 170A that, according to the logs, had flown for years until some mechanic discovered it had the wrong wings. They were L-19 wings. But the mechanic, who got the field approval when he discovered it in 2000 identified the wings as B model wings. And the mechanic never identified the fact the plane had B model flap controls and cables, B model struts, and a B model elevator.
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ghostflyer
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Re: O-300 over sized cylinders

Post by ghostflyer »

Bruce, please can you elaborate as I am confused . So how did you know you had L-19 wings and what fuel capacity were they. The L-19 had a 60 deg flap setting so the flap tracks were they retained or the 170b tracks in place. Another question how did your mechanic know about the different wing tips also. The reason is “I think” i use L-19 wing tips on my aircraft . my tips appear to be thinner than normal. my flaps are not normal as the skins are smooth without the “V “ in them but they are thick of at least 36 thou. All are hinged as a 170a.
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GAHorn
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Re: O-300 over sized cylinders

Post by GAHorn »

ghostflyer wrote:Bruce, please can you elaborate as I am confused . So how did you know you had L-19 wings and what fuel capacity were they. The L-19 had a 60 deg flap setting so the flap tracks were they retained or the 170b tracks in place. Another question how did your mechanic know about the different wing tips also. The reason is “I think” i use L-19 wing tips on my aircraft . my tips appear to be thinner than normal. my flaps are not normal as the skins are smooth without the “V “ in them but they are thick of at least 36 thou. All are hinged as a 170a.
I’ll try to alleviate Bruces’s burdern of response somewhat…as this subject was discussed several times here in the Forums….. David, Bruce once owned an airplane which had been reconstructed and/or repaired using parts from several airframes. If I recall correctly, it had an A-model dataplate but it strongly resembled a B-model because it had B-model tailfeathers and L-19 wings. The L-19 wings are virtually identical to B-model wings except for the flap arrangement which is hinged to 60-degrees on an L-19… (there are other minor differences such as provisions for rocket/flare dispensers which may or may not exist on all L-19s)….however Bruce already explained that B-model flaps had been installed on the L-19 wings. There is no difference in original wingtips except that lighting fixtures can differ…or not. (Remember, the B-model was developed from the L-19 (305) or the obverse, the L19 from the B-model…depending upon which story-teller is relating it.)

That airplane is typical of what is sometimes referred to as a “parts-plane”…an airplane constructed from several different salvaged airframes…but assembled and identified by one dataplate…which may or may not have ever had any relationship to the actual assembled parts. This was not uncommon in times-past…but is heavily frowned-upon by the authorities today….the practice of finding a dataplate and constructing an airframe which has no actual relationship to the original dataplate. The rule allows one to repair/reconstruct an airplane using salvage or replacement parts…but not with the intent of creating an entire airframe using a dataplate from a destroyed airplane to piece-together what is effectively a completely different airframe. That last description is (these days) viewed similarly as removing a dataplate form one airframe and transferring it to a different one….. as completely fraudulent and illegal …(although I am of the opinion FAA ignores examples which have existed in prior decades as too difficult and time-consuming to chase-down and prosecute. It’s a point to consider when inspecting a potential purchase, tho’.)
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TFA170
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Re: O-300 over sized cylinders

Post by TFA170 »

anejohn wrote: I had a conversation with a C170 owner who claimed he has over sized cylinders on his aircraft which gives an additional 10-15 horse power. Other forums have had general discussions about this topic and mentioned some Alaska folks have done this for a while.
As previously mentioned, I strongly suspect these are high compression pistons and not necessarily oversized cylinders. The "old way" was to use C85 pistons because they are the same bore size, but shorter stroke, with the same cylinder length - this means that C-85 pistons have a taller pin height (distance between wrist pin and piston crown). When installed in an O-200 or O-300, these pistons actually stuck out of the cylinders a bit, but were machined down for cylinder head & valve clearance. This increased the compression ratio. This mod was more common in the O-200 because it was a common engine in many racing leagues.

Well, the aftermarket caught on and Lycon/NFS began making aftermarket high compression pistons for the 4.0625" bore and stroke of the O-200/O-300 primarily for the racing and EAB crowd. With some ignition advance and the high compression pistons, O-300s have been claimed to make anywhere between 10-20HP difference. Difficult to nail down because these are all one-off engines and other modifications such as balancing and polishing ports, tuned exhausts, and other things add up too. The bottom line is, the O-300 can be made to produce close to 170HP at 2700 RPM and about 140-145HP at 2450 RPM....your stock 145HP is rated at 2700 RPM and you're really only getting about 120HP at takeoff RPM....so this is an improvement.
anejohn wrote:My question is how does the aircraft pass a 100 hour or annual inspection with out “Experimental” stamp on it. Is the mod so discreet that it is easily over looked or is this just hanger talk. If a C170 did have this mod what are the tale tell indications?
It would be fairly difficult for your average AP/IA to tell that you have aftermarket pistons if it was not documented in your engine log. If you change your timing, he might notice that and change it back to stock, but timing is easy to change.

I've heard anecdotally that this mod is about like taking 3" off your prop pitch. In other words, a 55" cruise prop "feels" more like a 52" prop for takeoff & climb - and so on. Takeoff and climb are allegedly improved noticeably, while cruise will likely remain mostly unchanged.
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eskflyer
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Re: O-300 over sized cylinders

Post by eskflyer »

agreed. lycon NFS 9-1 pistons as ive been told :lol: might just make that 20 plus HP. and that as ive been told is running on 87 octane real gasoline. was told that no timing needed to be changed and never any detonation. Cant remember who told me all this :D . and it all works with a sensenich ground adjustable 82" prop.
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Bruce Fenstermacher
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Re: O-300 over sized cylinders

Post by Bruce Fenstermacher »

ghostflyer wrote:Bruce, please can you elaborate as I am confused . So how did you know you had L-19 wings and what fuel capacity were they.
The rocket pod mounting hardware was a big clue. Standard 170B tanks and flaps.

To add to George's comment, I owned that airplane for some years. I studied that airplane inside and out comparing it to all other A and B models and it is the reason I learned so much about these airplanes. I didn't mean to speak badly about mechanics who can't identify different model parts, they more than likely are not experts in the airframe they are working on. I work on Cirrus every day and cant tell the difference between G2, 3, 4 or 5 and don't care. In the years I owned the plane and all my detailed searching down to counting rivets, I could never prove or disprove the data plate was not original to the fuselage.

The case of the engine and this thread if it had C-85 or Lycon pistons, a expert in those pistons could probably identify them from a C-145 piston with a borescope inspection, but maybe not.
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anejohn
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Re: O-300 over sized cylinders

Post by anejohn »

My bad, I probably misunderstood the conversation between cylinders vs pistons or the aircraft owner I had the discussion with didn’t know either.
In the event you had purchased an aircraft with an undocumented piston mod and found out about it later what would be the corrective action. Do a top end overhaul with OEM pistons and log book entry since I presume machining of the C85 pistons/ installed Lycon/NFS pistons are not an approved STC. Or do nothing and enjoy the additional horse power until a IA or A&P discovers it. A wink and a nod will do for the last statement. :wink:
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n2582d
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Re: O-300 over sized cylinders

Post by n2582d »

Bruce Fenstermacher wrote:… I don't recall how thee .015 over cylinders would have been marked. …
In SIL003 Continental explains how they mark cylinders to indicate oversized bores. But the explanation is for their PMA Lycoming and Pratt & Whitney cylinders, not for Continental engine cylinders. That said, I think these color codes are recognized across the industry. Plus 0.015” barrels should have gray fin markings. That, along with an orange flange to indicate chrome cylinders, is what I have on my O-300.

Here’s how the M-0 manual says oversized cylinders should be marked:
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TFA170
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Re: O-300 over sized cylinders

Post by TFA170 »

eskflyer wrote:agreed. lycon NFS 9-1 pistons as ive been told :lol: might just make that 20 plus HP. and that as ive been told is running on 87 octane real gasoline. was told that no timing needed to be changed and never any detonation. Cant remember who told me all this :D . and it all works with a sensenich ground adjustable 82" prop.
You don't HAVE to change your timing, but most small continentals respond well to a timing bump...I've also anecdotally heard that some folks have been known to open up their mufflers and fabricate straight through collectors and button them back up...they just sound a little louder...or so I've been told.
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TFA170
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Re: O-300 over sized cylinders

Post by TFA170 »

anejohn wrote:In the event you had purchased an aircraft with an undocumented piston mod and found out about it later what would be the corrective action. Do a top end overhaul with OEM pistons and log book entry since I presume machining of the C85 pistons/ installed Lycon/NFS pistons are not an approved STC. Or do nothing and enjoy the additional horse power until a IA or A&P discovers it. A wink and a nod will do for the last statement. :wink:
How would you find out if you weren't made aware of it by the seller? I think an AP/IA would be hard pressed to discover it, personally. However, if you wish your plane to be legal, the corrective action is to replace the pistons for those called for in the Continental overhaul manual.

Someone is allegedly working on an STC for high-comp pistons for the O-300...
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anejohn
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Re: O-300 over sized cylinders

Post by anejohn »

Thank you all for your comments on this subject and this is exactly why I needed to be apart your knowledge base. Hanger talk is great but sometimes information gained is flat out wrong. This all came about because a seller of an C170 claimed to have this undocumented mod which caused me to rethink an offer and start asking questions. Again thanks for the straight talk.
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Bruce Fenstermacher
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Re: O-300 over sized cylinders

Post by Bruce Fenstermacher »

anejohn if a prospective seller told me he had an undocumented modification such as this, one that could not be made right easily, I wouldn't be interested in the plane. We aren't talking about a plain with undocumented Cleveland brakes. That could be dealt with. I'd also consider what he might not be telling me.
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GAHorn
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Re: O-300 over sized cylinders

Post by GAHorn »

I have had the lovely experience of the head being blown off a cylinder during a night takeoff over a congested city in a rocky/wandering-river area…. and would not be interested in owning or operating an engine which had un-approved and undocumented increases in compressions. (And I do not know how an inspection procedure to detect a weakened barrel-to-head would be/could be trusted. I’d want new cylinder-assys as a minimum.)
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An originality nut (mostly) for the right reasons. ;)
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