O 300C value?

[Bruce Fenstermacher]

Well, glad that it's all worked out. Aren't you happy to have solved a 60 year mystery no one cared about until you asked "what is this?".

Keep copies of the letter of the engine logs.

[GAHorn]

According to the Continental rep, based on the serial number, this engine was manufactured on April 27, 1966 as an O-300-C. Apparently the "C" at the end of the s/n (32312-D-6-C) indicates that it is a O-300-C engine. This does not jive with current data plate nomenclature in which the first letter (in this case the D) indicates the engine model. (See SIL05-3A). If you were to get a new data plate from Continental IAW the Standard Practice Maintenance Manual, Appendix C-2.7.1 it would list the engine as an O-300-C-4. The rep said you could save $300 by replacing the "A" with a "C" on your existing dataplate but I think the value of the engine would be more than offset by doing it by the book.

I too have mounted my O-300 on an automotive engine stand. Mine was from Harbor Freight. But rather than using blocks under the magnesium engine sump and a couple of bolts through the prop flange I fabricated an "X" frame from 2" square tubing to attach to the C-170 mount. Attached is a PDF of my frame. The vertical dimension on my firewall was 24 3/16" rather than the 24.547" shown on the drawing. If one wants to copy the frame, use the drawing as a starting point -- verify dimensions with your mount or firewall rather than trust my dimensions.ENGINE STAND FRAME.pdf

(I realize this is awakening a “stale” thread…but having only just-returned from a long vacatiopn, I’m catching up on threads..)

Gary, I know you know this….but Serial Number and Model number areas on any dataplate (or log entry for that matter) are very different meanings.
A ‘D” in these engine Serial Numbers indicates a “Dampered” crankshaft…. while a “D” in a Model Number… indicates…Well….a specific Model engine.
The document you referenced SIL05-3A addresses “engine specification numbers that are stamped on the engine data plate following the engine model”… In other words, “Model” number stampings…not Serial number. (Under note “B” it actually states: “ These
codes do not affect the model of the engine.”

Well, After a short interlude, the engine is (drumroll)

An O300C

Met with the local FISDO who came and went over it with me. He's written me a letter to send off with the data tag to get an updated data tag. Question still stands as to how it ever got stamped A in the first place, and got signed off for 60 years and nobody noticed or cared.

The engine has found a new home too. Thanks for all the help guys.

Just to be a bit more “Picky”: HOW exactly, did the FSDO Inspector make that determination? Was that a personal inspection? …or did he have some other reference or input from somewhere? …. Because Everyone present in this discussion already Knew and agree it is a “C” engine. (FSDO opinion offers nothing new in that regard.
(In fact that is exactly what “wingnut” correctly pointed-out…. Anyone in authority (TCM, FAA, A&P/IA, or even the Owner) can inspect the engine and “find” that it is a “C” and correct the records And the Datatag.)

The issue under discussion is WHY it has an “A” datatag…. WHEN did it get that “A-datatag’….and WHEN (if it was an A converted to C… was it not properly recorded and datatag stamped accordingly…. OR… if TCM (or anyone else) claims that according to their racrods it has Always Been a “C” engine…. WHY does it have the Improper Datatag? …and WHY does a TCM person believe a Serial number identifies a Model number which Differs from the Public Records and Datatag? (I.E., if internal records at TCM indicate this engine has Always been a “C”…and if the datatag is original… then why was it incorrectly identified and Why doesn’t TCM offer to correct their mistake?)

Curious people want to know.