6 or 8 bolt crankshafts-

[Exploreit2]

OK, guys here it goes (be nice!):

A guy sent his C-145 to an engine shop for an overhaul. Crank ended up being bad (8 bolt). He found a 6 bolt crank at a fair price and had the engine finished with it.

So, here are the questions (they may be easy to get an answer for or not):

First off, with the original engine tag, is the engine still legal now that it has a different crank? Well, same crank just a 6 bolt instead of the 8 bolt.

Second, what has to be done with the plane now? Obviously a new prop, and spinner. Is that it or does modification paperwork need to be done?

Third, how many if any C170 left the factory with the 6 bolt cranks?

Fourth, are most of the C170 in the air still flying with an 8 bolt crank?

I couldn't answer all of these questions so I decided to see what you all have to say about this. Hopefully its not too controversial.

[Bruce Fenstermacher]

I'll take a stab at it JB

First the engine has essentally been changed from an 0-300A to an 0-300C. The basis of approval to do this is a Continental Service Bulliten M75-6R. He needs to get it and of course a 337 should have been done by the engine shop following this SB. So he should now be the owner of a 0-300C.

Now you need a basis of approval to put the 0-300C on the 170 as it was not an approved engine. That would be an STC which I belive is held by an Association member.

If th STC doesn't cover the prop then he'll need an approval to use the 6 bolt McCauley EM7355 which George says is the eqivalent to the standard 8 bolt McCauly prop for the 170.

George happens to have this engine/prop combo in his plane.

[Exploreit2]

Bruce, Thanks for the info. But the engine actually went in to the shop as a C-145 not an O-300. Not sure if that matters. Does he need to change the engine tag? So the engine shop is responsible for the Continental Service Bulliten M75-6R and 337.

How can I find out more information on the STC for the engine in the C170? And as far as props go, its just the early C172 prop selection: Standard prop: EM7653 Cruise prop: EM7655 Climb prop: EM7652

Its my understanding that ALL Cessna 170's, A and B models left the factory with C-145. So does that mean that anybody with an O-300 installed, changed the engine tag or has this STC?

[Bruce Fenstermacher]

First a C-145-2 is a 0-300-A. If you have any other engine installed other than what is specified on the Type Certificate, a C-145-2, 2H or 0-300-A are the choices as I remember, you must have some type of approval. The approval could be either one based on a 337 for that aircraft or an STC which also might me for just one aircraft.

What I was trying to say is by what authority did the engine shop change your c-145/0-300-A to an 0-300-C.

Perhaps they already used the SB and hopefully filed a 337 or your engine is unairworthy for a certified aircraft. They just can't change out parts without some approval. The shop did know you where putting this in a certified aircraft didn't they?

The SB and or Continental will spell out what if any change should be made to the data plate but I'm sure something should be changed.

From one of gahorns' earliar posts in another topic "As for the O-300-C/D STC, it is available at very reasonable cost from it's owner, Ron Massicot, past president of TIC170A. (Look him up in the Directory.) Last I heard he charges $35 to TIC170A members for the O-300-D STC."

The EM7355 prop I posted earliar was also from a gahorn post. Perhaps he ment EM7655. I'm sure George will chime in here at some point.

I would talk to your engine shop about the paperwork on your engine. Then I'd call Ron Massicot and see exactly what his STC covers i.e. the prop.

[zero.one.victor]

First of all,a C-145-2 is NOT an O-300A, it is a C-145-2. It may be pretty much the same as an O-300A,but it is a C-145-2,like the data plate sez.
Secondly,installing a 6-bolt crank does not turn a C-145-2 into an O-300C. It all depends how they write up the overhaul. I would guess that it could be handles thusly: "replaced crankshaft with airworthy crankshaft p/n xxxxx ",if this is an approved replacement part as per TCM overhaul manual and SB's. This isn't the first time this substitution has had to be done.The data plate will still have the same serial number & model engine--C-145-2.
JB,from your tardemart post,it sounds like you had 2 8-bolt cranks,one was bad & one went to your buddy. Now you have a 6 bolt,and need a 6 bolt prop. Why didn't you keep the good 8 biolt crank,& give the 6 bolt crank to your buddy?

Eric

[Exploreit2]

Eric, its a long story. Basically, he had to have a crank immediately to get his plane back in the air ASAP because he was about to loose his mother and was flying back and forth all the time to see her. At the time I thought I had two good 8-bolts and didn't think anything of it.

Does that make sense?

Thanks for you help! I will take all I can get

[GAHorn]

IF it's possible to convert an engine from one model to another, ...the data plate shall be stamped to indicate the change.
Per the TCM SB M75-6R1:
"SUBJECT: CONVERSION OF ENGINES FROM ONE MODEL TO ANOTHER
MODELS AFFECTED: All Models
Gentlemen:
Although we have never recommended conversion of engines from one model to another, we have had over the
years, many inquiries on whether or not it is permissible to convert from one model to another. As a result, in order
to maintain a good relationship with owners who desire to convert their engines, we have issued previous bulletins
granting that certain conversions can be accomplished, such as:
1. Within a basic engine family, it is permissible to convert from one dash number (or letter) to
another as long as it is accomplished with parts currently approved for the model to which the
engine is being converted.
2. In the case of the "E" series engines, any conversion of an E-185 to an E-225 will require a new
serial number, which can only be issued by Teledyne Continental Motors. For information on
how to procure a new nameplate, see our bulletin M75-5.
3. On other models, impression stamp the letter "C" after the existing model letter (or number) and
then impression stamp the new designation letter per the following example:
IO-470-U to IO-470-V = IO-470-UCV
4. Do not alter serial number or suffixes."

Second, I believe both Eric and Bruce have made excellent points. The overhauler should have properly documented the conversion and should have excersized the paperwork correctly including a basis of approval. Otherwise, You should go to the overhauler to provoke them to do so.

It's an entirely seperate problem if the mfr (TCM) will not approve a C-145 conversion to the O-300 series, or if they will not allow the O-300 C/D crank to be installed into the C-145 engine, but one scenario possible is they might allow the C-145 to retain it's identity with an O-300-C/D crank. (They might consider it an approved replacement part. Unlikely they'd allow it without a designator change, in my opinion, but they might.)
In any case, FIRST the engine must be made to conform to a certificated design and/or approved substitute,....THEN the installation of that particular engine model into the aircraft must find approval. The most likely route would be field approval or STC. That approval will also have to address the necessitated change of prop and/or any other accessories.
In any case, this matter may not be allowed to sleep. Until the approvals are obtained for the engine rebuild/conversion, and until the engine installation into the aircraft, and the associated prop, etc. are also approved for the installation, ...the aircraft is considered unairworthy (by the authorities. This may not be an unairworthy combination in practice, but it is in the eyes of the legal authorities until the paperwork is approved.)
(And I guess I'll have to find my previous post to correct the typo error that Bruce found. The post should have said EM7655 rather than 7355. Thanks Bruce!)
P.S. My installation is a field approval.