O-300A vs O-300D identification

[anejohn]

Came across a 1953 C170B which the seller claims has a O-300D engine. I have a copy of the maintenance logs and engine log book and there are no 337 forms describing a O-300D being installed. There are no Venturi tubes and in 1993 the engine log shows the original O-300A engine being overhauled and as of today indicating 343 hr SMOH. 2019 logs show a ER 14-50 alternator replaced the generator but doesn’t show engine series. A cockpit photos show a key start & no pull start.
My question is did the O-300A engine incorporate a vacuum pump explaining the lack of Venturi tubes or did someone install a O-300D engine and not put it in the log book? Is there any other identifiable markings such as a stamp or crank shaft flange type to key up on and identify the series?

[Bruce Fenstermacher]

Someone could have done several things. The answer to your question an 0-300A never had a vacuum pad to install a pump in a stock configuration.

The first place to look is your engine data plate. What is the serial number? Take a picture so we can see it.

Look at your starter. Is the starter motor in line with the crank shaft or is it 90° to the crank? If in line you it is not a D, it could be a C or less configuration. Or if it has a vacuum pump on the back of the engine the only way that could happen is with the angle starter which incorporates a vacuum pump pad. How many bolts hold the prop on? A C or D model should have a 6 bolt crank, all others an 8.

So with the information on the data tag we should be able to determine what the engine is. Is it a 0-300A or D or something else. Then depending on what that tag tells us the answers to the other questions will confirm the engine has the correct parts installed or not.

No matter what configuration it has, it could be made legal. How hard that would be depends on what other documentation it has, the willingness for someone with the knowledge and authority to gather all the required document to show the configuration is legal and document it.

[anejohn]

Just received a photo of the engine data plate clearly showing its a O-300A /145HP. I was under the impression that if the Venturi tubes were missing it must be a O-300D series because this engine incorporates the vacuum pump pad that is missing on the other other series engines. After looking a little closer to the cockpit instruments pictures, I noticed there wasn’t a turn & bank indicator (vacuum driven) and the artificial horizon and heading indicators were both electric driven. So no need for the venturies.
Wish they took photos of the starter as I would like to have seen your description about how the starter sits relative to the engine.

Thanks for your help

[Bruce Fenstermacher]

If you have a picture of your instrument panel and the pull starter knob has been removed, this plane likely has an angle starter or a STC'd starter such as a B&C. Why not just ask what the engine has, I'd want to know. Top is the 0-300-A, B or C with straight starter, bottom is the 0-300-D with the angle starter

[GAHorn]

anejohn, while the type installed starter is One indicator… a Significant item not to be overlooked is the Crankshaft and Propeller combination.

The O300-A engine utilized an EIGHT bolt prop flange and associated propeller…. While the O300-D engine utilized a SIX-bolt prop flange and propeller.

I mention this because of the possibility of nomenclature errors. These engines can be “converted” from one model to another if the mfr’s Service Instructions and Bulletins are followed which allow that conversion. To convert an A engine to a D engine would entail a crankshaft AND an accessory-case (which accommodates the angle-starter and vacuum pump).
But an A engine might have a D crankshaft …. WithOut fully complying with the other changes that complete the conversion to an O300-D….and which might still have it’s datatag marked as an “A”. The aircraft’s associated ENGINE LOG should be consulted….but it would not be unheard-of to discover that modifications have occurred without proper documentation. (why we inspect before purchase)

In the event of complete model conversion, the engine Datatag should be over-stamped and would have a Suffix such as “ O300A C D” meaning “Converted to D”. (Of course, if it were an original C145 engine we could really get into muddy water.)

[anejohn]

Thanks for that detailed explanation, definitely a keeper for the O-300A thru D identification file. Since this is not my aircraft I didn’t feel comfortable advertising someone else’s info by posting the data tag complete with a serial number. I edited the screen shot so not to include a serial number for others to view. At the top left corner it’s clearly stamped O-300A with NO over stamp D. Again the reason I went down this road is because the owner said it was a O-300D engine but there were no Engine log entry nor was there a 337 supporting that. So thanks for all the help from the forum. My new task is to locate a 337 form on the installation of a Sportsman Leading STC. It’s in the airframe log dated 8/2022 but I don’t have a supporting 337, Hmmm. Also any comments/ suggestions about missing logs? Airframe 1953 to 19960 are missing. Engine 1953-1985 missing.

[n2582d]

Are you saying that the FAA doesn't have record of the Sportsman STOL kit being installed? You have checked here, right?How to see Aircraft Records, Mantenance, Registration and so much more, FREE and instantly

If there is no record of the STC in the files but it is documented in the airframe logbook call or write Stene Aviation to get a copy of the necessary STC paperwork. My STOL kit doesn't have a serial number associated with it but it does have an invoice number. Stene should have the aircraft N number and serial number in their files to verify that they have sold a kit for that aircraft. Then, assuming there is no record of this with the FAA, a 337 will need to be filed with the FAA in OKC.

[cessna170bdriver]

I noticed you said the cockpit photo shows a key start. Key or push button start on an O-300A is possible with either of the aftermarket “lightweight” starters.

[GAHorn]

It seems to me that a “seller” has an airplane with incomplete and inaccurate maintenance records….. and You or a friend might still want to buy it..? If so, be prepared to own a very questionable airplane unless you spend time and money on it to make it legal.

[anejohn]

Sorry for the late response, wanted to follow up with contacting Stene Aviation, the STC owner ( great suggestion) for a timely response. Unfortunately it’s been 7 days since my initial emails and voice messages. I have not heard back. So as it stands, a Sportsman leading edge kit was installed with a logbook entry but NO accompanying 337 form in the aircraft registration.
As for the “Pull or push button start, I can’t tell from the pictures I see. Looking over the Aircraft Registry I don’t see a starter STC, just a new Plane Power ER 14-15 alternator conversion installation recently.
Besides 1953 to 1965 missing log books, the missing 337 documentation, two years out of annual, a possible lien in addition to the last over haul in 1993, I backed away.

Thanks for your help.

[GAHorn]

Sounds like you’ve made a wise decision.

You’ll find your “perfect” plane…. have faith. and patience.