O 300C value?

[GAHorn]

George,
Explain why a field overhaul can't be called an overhaul in your opinion.

I didn’t say that it couldn’t. (or at least I didn’t intend to say that if I did.)

What I intended to convey is that in common parlance people often refer to an engine having “XXX hours since overhaul” …. when in-fact, the engine only rec’d a “major repair”….not a full overhaul. It is Very Rare that these old C145/O300 engines receive “overhaul” per the TCM and FAA definitions.

Furthermore, engines which Are “overhauled”…should be described as to “new” or to “serviceable” limits.

TCM is Very Specific about the Mandatory replacement items that must be included in an actual “overhaul”…. while similar work might be performed without full replacement of mandatory parts in a hangar or shop somewhere….work that might be quite satisfactory for another full run of TBO….. but does not actually meet the requirements of the term “overhaul”. (An example might be crankcase Through-Bolts. Many hundreds of these engines were rebuilt with new piston, rings, bearings, seals, gaskets, cylinders, valves, etc etc etc…. but reassembled with throughbolts that were re-used “as is” or perhaps even NDT’d and reinstalled. But that second example may not legally use the term overhaul. It actually should use a Form 337 to describe a “Major Repair”.

The same is true of certain accessories that might be attached to that engine. Was it an actual “overhaul” if the mags and carb were only “gone thru” on that shop-bench by that A&P and reinstalled with new plugs, points, condenser and new float and gaskets? Ans: No.

Colloquially we might say it was “overhauled” when in reality it was “repaired”. This becomes especially critical when equipment is intended for commercial use (such as Pt 135) instead of Pt 91 private use.

Anyway, my earlier comments in This Discussion-thread was for the intent to distinguish differing values of similar engines, nothing else.

[Lhorn]

FYI I have confirmed through record search that this engine is a 0-300 C model and has always been a 0-300 C model.

Hey Bruce, curious how you came to this conclusion....

[GAHorn]

FYI I have confirmed through record search that this engine is a 0-300 C model and has always been a 0-300 C model.

Hey Bruce, curious how you came to this conclusion....

IMG_4669.jpeg

[Bruce Fenstermacher]

FYI I have confirmed through record search that this engine is a 0-300 C model and has always been a 0-300 C model.

Hey Bruce, curious how you came to this conclusion....

I did a record search of N7681X which is a 172B. It came from the factory with a 0-300-C. That is what Cessna installed and only a C or D is approved for a 172B. There was no evidence in the database the original engine was ever changed out until it was removed for a Franklin engine. And if the original engine had been replaced with another, don't you think they would have installed a legal engine, not an A which is not legal per the TCDS and there was no other approval in the records that should have been there if they had one. I felt very confident that your engine was the original C model from N7681X and that is why every one was calling it that.

That is until I saw the picture of your engine data plate and it was stamped -A

[GAHorn]

Yeah…. this A-engine was not likely the engine it left the factory with…. but instead, is a later replacement engine (and not well-documented, despite the likelihood the combination was entirely airworthy except on paper.)

It may be that this A-engine rec’d a 6=bolt crank so the airplane owner could use the same prop.

[n2582d]

George,
Explain why a field overhaul can't be called an overhaul in your opinion.

I didn’t say that it couldn’t. (or at least I didn’t intend to say that if I did.)

What I intended to convey is that in common parlance people often refer to an engine having “XXX hours since overhaul” …. when in-fact, the engine only rec’d a “major repair”….not a full overhaul. It is Very Rare that these old C145/O300 engines receive “overhaul” per the TCM and FAA definitions.

Furthermore, engines which Are “overhauled”…should be described as to “new” or to “serviceable” limits.

TCM is Very Specific about the Mandatory replacement items that must be included in an actual “overhaul”…. while similar work might be performed without full replacement of mandatory parts in a hangar or shop somewhere….work that might be quite satisfactory for another full run of TBO….. but does not actually meet the requirements of the term “overhaul”. (An example might be crankcase Through-Bolts. Many hundreds of these engines were rebuilt with new piston, rings, bearings, seals, gaskets, cylinders, valves, etc etc etc…. but reassembled with throughbolts that were re-used “as is” or perhaps even NDT’d and reinstalled. But that second example may not legally use the term overhaul. It actually should use a Form 337 to describe a “Major Repair”.

The same is true of certain accessories that might be attached to that engine. Was it an actual “overhaul” if the mags and carb were only “gone thru” on that shop-bench by that A&P and reinstalled with new plugs, points, condenser and new float and gaskets? Ans: No.

Colloquially we might say it was “overhauled” when in reality it was “repaired”. This becomes especially critical when equipment is intended for commercial use (such as Pt 135) instead of Pt 91 private use.

Anyway, my earlier comments in This Discussion-thread was for the intent to distinguish differing values of similar engines, nothing else.

Reciprocating Engine Overhaul Terminology and Standards

[Lhorn]

Soooo, no logbook entry was ever made on the crank swap in this engine. I think I have a clear game plan to get this straightened out, thanks to all the info provided. Seems straightforward too and I appreciate all the help on this. I'd like to see it go to a new home and I'm not too worried about top dollar, just whatever is fair. Would I pay to have the engine inspected, or should I just sell it as is? I could have my mechanic pull a cylinder and get photos I guess. Easier to just have it go to a new home. I'd assume anyone who bought it would overhaul before putting it back into service.

[GAHorn]

I’d suggest you sell it “As Is”. But you’ll probably sell it easier if the paperwork was corrected.

[Lhorn]

Agreed simplest would be "as is," and also seems simple enough to correct the logs by following the Continental Service Bulletin (SB) M75-6 to convert it to a C model, making a log entry, and then correcting the data plate. My IA is gonna look into it for me to make sure it's as easy as that.

.

[n2582d]

To me this seems to be a Occum’s Razor situation. Amazing mental gymnastics to say this is or ever was a O-300-A are worthy of an Olympic metal.
Evidence supporting this engine to be an O-300 A with a O-300 C crankshaft
1.) O-300-A stamp on data plate.

Evidence supporting this engine to be an O-300 C
1.) Continental Motors says the serial number 32312 is a O-300-C shipped on 4/27/1966.
2.) According to Continental the “C” suffix on the serial number 32312-D-6-C indicates it’s model number to be a O-300-C.
2.) This is not an original data plate as it says “Teledyne Continental”. Continental was part of Teledyne between 1969 and 2010 — after the period they manufactured O-300-A engines.
3.) All paperwork associated with the engine refer to it as an O-300-C.
4.) There is no paperwork to indicate that it was converted from an A to a C. Such paperwork should be on file with the FAA as a major alteration.
5.) There is a 337 dated April 30, 1977 documenting the installation of an O-300-C serial number 32312 on a 1956 C-172. A major alteration form would not be required if the installation was for a O-300-A.
6.) If this was an engine converted from an A to a C the stamp shouldn’t say O-300-A, it should read O-300-ACC.

Your explanation here seems most probable to me,

I'm vaguely remembering a conversation I had years ago, and someone said at one time that you could buy O 300 A data tags, but not C, and he theorized the tag had been replaced, and bore the available A stamp.

If you try to get a new data plate from Continental, who views this as a O-300-C, do you think they are going to give one stating it is a O-300-ACC (A converted to a C)?

[GAHorn]

To me this seems to be a Occum’s Razor situation. Amazing mental gymnastics to say this is or ever was a O-300-A are worthy of an Olympic metal.
Evidence supporting this engine to be an O-300 A with a O-300 C crankshaft
1.) O-300-A stamp on data plate.

Evidence supporting this engine to be an O-300 C
1.) Continental Motors says the serial number 32312 is a O-300-C shipped on 4/27/1966.
2.) According to Continental the “C” suffix on the serial number 32312-D-6-C indicates it’s model number to be a O-300-C.
2.) This is not an original data plate as it says “Teledyne Continental”. Continental was part of Teledyne between 1969 and 2010 — after the period they manufactured O-300-A engines.
3.) All paperwork associated with the engine refer to it as an O-300-C.
4.) There is no paperwork to indicate that it was converted from an A to a C. Such paperwork should be on file with the FAA as a major alteration.
5.) There is a 337 dated April 30, 1977 documenting the installation of an O-300-C serial number 32312 on a 1956 C-172. A major alteration form would not be required if the installation was for a O-300-A.
6.) If this was an engine converted from an A to a C the stamp shouldn’t say O-300-A, it should read O-300-ACC.

Your explanation here seems most probable to me,

I'm vaguely remembering a conversation I had years ago, and someone said at one time that you could buy O 300 A data tags, but not C, and he theorized the tag had been replaced, and bore the available A stamp.

If you try to get a new data plate from Continental, who views this as a O-300-C, do you think they are going to give one stating it is a O-300-ACC (A converted to a C)?

This response is not a disputation of these good points,…and that is Excellent Sluething….

just in the Interests of Good discussion …and illustration of how things can be different than what might be considered “conclusive-assumptions”….Not to be taken as disagreement.. I’m offering these comments for contemplation…:

1.) Continental Motors says the serial number 32312 is a O-300-C shipped on 4/27/1966. That serial number depiction is incomplete. The Whole SN is “32312 D-6- C”
2.) According to Continental the “C” suffix on the serial number 32312-D-6-C indicates it’s model number to be a O-300-C. Accoring to WHOM at Continental? Telephone persons verbal comments don’t carry authority. And..if that is So…then WHY is that “C” in the SERIAL NO LINE…and not in the MODEL line of the datatag..??
2.) This is not an original data plate as it says “Teledyne Continental”. Continental was part of Teledyne between 1969 and 2010 — after the period they manufactured O-300-A engines. It still might be an original dataplate… IF the entire SN is considered, as that would be a DIfferent engine than SN 32312.
3.) All paperwork associated with the engine refer to it as an O-300-C. That may be because an Error, once committed, is projected onward repetitiously. And, that statement is Not Correct. The Form 337 is part of the paperwork..and Specifically Identifies this engine as “O 300 A”
4.) There is no paperwork to indicate that it was converted from an A to a C. Such paperwork should be on file with the FAA as a major alteration. ”Should be” is a critical phrase. Lack of paperwork is a lack of information….Not proof of what is assumed. There are Great-Quantities of “missing” paperwork at FAA-OKC.
5.) There is a 337 dated April 30, 1977 documenting the installation of an O-300-C serial number 32312 on a 1956 C-172. A major alteration form would not be required if the installation was for a O-300-A. But a 337 IS req’d if such subtitution DID occur. The fact a 337 does exist supports the argument this engine is not the original engine. Since the complete SN was not utilized, the 337 is not accurate. The only proof that 337 provides is that a previous engine was replaced with one SN 32312, which is also likely recorded in error.
6.) If this was an engine converted from an A to a C the stamp shouldn’t say O-300-A, it should read O-300-ACC. Agreed. Again, “Should” is pertinent. But this is the actual problem: The mx records are erroneous in many ways and in multiple entries.

Your explanation here seems most probable to me,
Lhorn wrote: ↑Wed Apr 08, 2026 4:30 pm
I'm vaguely remembering a conversation I had years ago, and someone said at one time that you could buy O 300 A data tags, but not C, and he theorized the tag had been replaced, and bore the available A stamp. The “vague conversation remembered” refers to an anecdotal belief. It is unlikely Continental would re-issue a replacement datatag which Continental KNEW to contain erroneous information. IF Continental re-issued a replacement datatag….it is Most Likely they would have issued only a Correct datatag. This datatag, if a replacement, was re-issued identifying the engine as O-300-A…. regardless of it’s then-current configuration.
If you try to get a new data plate from Continental, who views this as a O-300-C, do you think they are going to give one stating it is a O-300-ACC (A converted to a C)? This again fails to identify “Who” at Continental “views this as a O-300-C”… a telephone receptionist is hardly an authority…..and further, this fails to support the actual configuration of the engine. For Instance: IF Continental RE-Issued a replacement datatag….the Better Question is “Why would they issue one they Knew to be an Erroneous one?” Answer: They wouldn’t. In fact, to obtain a replacement datatag, it is a Requirement the engine Must Be Correctly Identified! (This subject has been discussed in other threads. Engines may be fully identified based upon things such as installed-accessories and repair records that match the condition of the no-datatag-engine. Example: an engine missing it’s dataplate…but accompanied by logbooks recording a previous installation of Magnetos with SNs 12345 and 6791 ..and with a Jasco alternator serial no. 12345… etc etc…. pretty-well Identifies the engine as the same one to which the logbook applies by Model AND Serial Number.

I hope these added comments by me are taken as they are intended: An arms-length discussion of how mis-identified things can be further complicated by continued errors….not criticism of others comments and observations.

If Continental legal or certfication dept believes this is and has always been a O-300-C…then They SHOULD ISSUE a NEW datatag and REQUIRE RETURN of the erroneous one. IMO

[cessnut]

A guy could check the cast date on the case, although I'm not exactly sure what year they stopped building O-300As.

[Lhorn]

Highly interesting GAHorn, and very insightful.
I guess I need to take this to Continental next.
Maybe I can get someone over there to take a look at this thread to better see just how far this discussion has gone. The fact that nobody saw a problem with it, at least not worth addressing, for almost 50 years says something. I'll try and start my way through the system over at Continental and see if I can find someone willing to search through the annals over there. May shed some light.

[n2582d]

just in the Interests of Good discussion …and illustration of how things can be different than what might be considered “conclusive-assumptions”….Not to be taken as disagreement.. I’m offering these comments for contemplation…:

1.) Continental Motors says the serial number 32312 is a O-300-C shipped on 4/27/1966. That serial number depiction is incomplete. The Whole SN is “32312 D-6- C”My bad. I was being lazy. I did give Continental the entire s/n with the D-6-C suffix.
2.) According to Continental the “C” suffix on the serial number 32312-D-6-C indicates it’s model number to be a O-300-C. Accoring to WHOM at Continental? Telephone persons verbal comments don’t carry authority. Yeah, I suppose the janitor could have picked up the phone when I called the Continental number for Tech Services. My email contact was Tim Owen, "Product Support Engineer". He was the instructor who taught the two week Level 1 and Level 2 Factory Training Courses which I attended several years ago. And..if that is So…then WHY is that “C” in the SERIAL NO LINE…and not in the MODEL line of the datatag..?? That's the essence of what we are trying to figure out. I feel the serial # line is correct and the model # line incorrect. You think it's the other way around. As I stated below, my theory is that LHorn is correct when he states, "I'm vaguely remembering a conversation I had years ago, and someone said at one time that you could buy O 300 A data tags, but not C, and he theorized the tag had been replaced, and bore the available A stamp."
2.) This is not an original data plate as it says “Teledyne Continental”. Continental was part of Teledyne between 1969 and 2010 — after the period they manufactured O-300-A engines. It still might be an original dataplate… IF the entire SN is considered, as that would be a DIfferent engine than SN 32312.As stated above, the entire s/n was relayed to Continental. I also would be very surprised if Continental duplicated the 5 digit s/n sequence on engines with different suffixes.
3.) All paperwork associated with the engine refer to it as an O-300-C. That may be because an Error, once committed, is projected onward repetitiously. And, that statement is Not Correct. The Form 337 is part of the paperwork..and Specifically Identifies this engine as “O 300 A” I was mistaken. The original entry on the first page of this thread shows a logbook entry describing the removal of this engine from N7408A. There it refers to the engine as a O-300-A. But then LHorn says, "It is a C model, the mechanic made a typo on his logbook entry." Regarding the 337 form. It says an O-300-A was removed from N7408A and this O-300-C was installed. Bruce also found that an O-300-C with this serial number was removed from N7681X.
4.) There is no paperwork to indicate that it was converted from an A to a C. Such paperwork should be on file with the FAA as a major alteration. ”Should be” is a critical phrase. Lack of paperwork is a lack of information….Not proof of what is assumed. There are Great-Quantities of “missing” paperwork at FAA-OKC.
5.) There is a 337 dated April 30, 1977 documenting the installation of an O-300-C serial number 32312 on a 1956 C-172. A major alteration form would not be required if the installation was for a O-300-A. But a 337 IS req’d if such subtitution DID occur. The fact a 337 does exist supports the argument this engine is not the original engine. Since the complete SN was not utilized, the 337 is not accurate. The only proof that 337 provides is that a previous engine was replaced with one SN 32312, which is also likely recorded in error. The complete s/n was used.

IMG_1740.jpeg

6.) If this was an engine converted from an A to a C the stamp shouldn’t say O-300-A, it should read O-300-ACC. Agreed. Again, “Should” is pertinent. But this is the actual problem: The mx records are erroneous in many ways and in multiple entries.

Your explanation here seems most probable to me,
Lhorn wrote: ↑Wed Apr 08, 2026 4:30 pm
I'm vaguely remembering a conversation I had years ago, and someone said at one time that you could buy O 300 A data tags, but not C, and he theorized the tag had been replaced, and bore the available A stamp. The “vague conversation remembered” refers to an anecdotal belief. It is unlikely Continental would re-issue a replacement datatag which Continental KNEW to contain erroneous information. IF Continental re-issued a replacement datatag….it is Most Likely they would have issued only a Correct datatag. This datatag, if a replacement, was re-issued identifying the engine as O-300-A…. regardless of it’s then-current configuration.
If you try to get a new data plate from Continental, who views this as a O-300-C, do you think they are going to give one stating it is a O-300-ACC (A converted to a C)? This again fails to identify “Who” at Continental “views this as a O-300-C”… a telephone receptionist is hardly an authority…I believe I pressed "2" for Tech Support after calling the Continental phone number rather than "O" for operator...and further, this fails to support the actual configuration of the engine. For Instance: IF Continental RE-Issued a replacement datatag….the Better Question is “Why would they issue one they Knew to be an Erroneous one?” Answer: They wouldn’t. In fact, to obtain a replacement datatag, it is a Requirement the engine Must Be Correctly Identified! (This subject has been discussed in other threads. Engines may be fully identified based upon things such as installed-accessories and repair records that match the condition of the no-datatag-engine. Example: an engine missing it’s dataplate…but accompanied by logbooks recording a previous installation of Magnetos with SNs 12345 and 6791 ..and with a Jasco alternator serial no. 12345… etc etc…. pretty-well Identifies the engine as the same one to which the logbook applies by Model AND Serial Number.

I hope these added comments by me are taken as they are intended: An arms-length discussion of how mis-identified things can be further complicated by continued errors….not criticism of others comments and observations.

If Continental legal or certfication dept believes this is and has always been a O-300-C…then They SHOULD ISSUE a NEW datatag and REQUIRE RETURN of the erroneous one. IMO

[GAHorn]

Then it appears that Tim Owen, Product Support Engineer …….is either too busy to be “bothered” with this matter…..is …(unlike the janitor) … being sloppy….or ….does not know the difference between a Serial and a Model.

If this engine records and datatag have such glaring errors…then Continental should request the erroneous datatag Be Returned to them…and they should correct their own error they (presumed) made when they issued the erroneous replacement tag presently on the engine.

It’s an unfortunate commentary on the current state of expertise at Continental, and the level of interest or commitment they have on their older products.

Re: Item 5 in the post above: The Form 337 cannot be relied upon as accurate when it contains such errors. It has RE-Identified THIS engine as an O-300-C by utilizing the Serial No 32312-D-6-C. Why is that an error?
Because Engine Serial No. 32312=D-6-C is NOT an O-300-C… as stated on the engine datatag rivetted to the case: SN 32312-D-8-C is an O-300-A.

It’s a vicious circle error and should be corrected. (I don’t recall if crankshafts have I.D. numbers, but if so, then (in the assembly-records) this crank should be paired with this engine if the engine really were originally a “C”. Those records are probably no longer available.)