0300D in 1951 170A

[prairiechicken]

Hello all,

I am in need of some advice from the community.. The C-145 in my '51 A model has 1900+ hours on a many years old overhaul, and ~1200 hours on a few years newer top end. I have an opportunity to purchase an O300D from a 172, that has ~2800 hour SMOH/Since new, for what I would consider to be a modest price. The accessories are included in the purchase price. My 145 is running ok on condition, but I realize it won't last forever. If I buy the O300D as a core, my mechanic has offered to let me help with disassembly, adjusting labor costs accordingly. I am wondering what the community's opinion is on a project like this. I would like to have the horsepower that the O360 would offer, but the plane is largely unmolested, and I would have a hard time making the modifications necessary for that engine, also I feel that it is cost prohibitive for my needs. A couple advantages I consider with buying the O300, I can take my time with the overhaul, saving a large financial burden all at once, also I can keep flying in the meantime, provided the current engine doesn't give up on me The option to have constant vacuum for instruments also interests me.

It would also make me feel better taking my family flying if I know the condition of the engine that keeps that stick turning up front Sorry for such a long winded post, I look forward to all of your opinions.

Ty

[c170b53]

I would say, it's a total unknown as to the true state of your engine until it's torn apart. Well almost a total unknown as you say it had a newer top end but were those new cylinders at the top or reconditioned ? In my opinion, it's the cost of parts and part availability that's driving the cost of overhauls to levels which are hard to swallow. So, it's great your mechanic would include you in the work, so that you'll have a greater knowledge level, but likely your assistance won't vary the end dollar result that much.
There's also nothing to say this new to you 0-300D is any better than your present engine. If I can do the math, the last year for that engine in a hawk was 1967. That's 51 years possibly more, if I understand you correctly when you say since new. So if your present engine is older than that since tear down and it's been relatively trouble free then likely you should have no problem possibly winning the next powerball.

[n2582d]

Ty, If I'm not mistaken, I think you're also going from an 8-bolt prop to a 6-bolt one. Does the prop come with the engine?

[Bruce Fenstermacher]

Gary is correct, you would need a prop to fit the 6 bolt crank. And you will need the Associations STC, $75 to members, to make the installation legal. You would be converting from a cable pull start to an angled starter with a electric push button start, so those electrical mods would be necessary. Couple of hours labor and cost of wire, solenoid, push button or key switch. The cost of the prop is the big ticket item. Of course the prop cost could be offset a little selling your current prop.

So you have the cost of buying the 0-300-D and you have the cost of the prop before you start overhauling expense. You have to figure out if the time out of service to rebuilt the engine you already have when the time comes, is worth it. And you'd already be setting the course you intend to take. What happens if 2 months from now a C-145/300A falls in your lap. Maybe even one recently overhauled with lots of time left.

What to do, what to do?

[c170b53]

Lately there's been more than a few high time engines advertised for sale on Barnstormers and elsewhere. Again a total dart throw, blindfolded. Oil sump condition likely the biggest part of the gamble out there.

[GAHorn]

Don't forget that $600 spinner changeout also.

Ty, at the risk of repeating myself...(I know no one present thinks I would do that tho'...

... Just what is it about a vacuum pump that makes you feel safer?

Is it the fact that NTSB and FAA accident reports find vacuum pump failures one of the most-common initiators of instrument-failure loss of control?

Is it because zero-zero takeoffs in a single-engined airplane are so much safer with a vacuum pump?

Is it that vacuum pumps don't ice-up when the rest of the airplane does?


Why anyone would deliberately take off in less than 1-mile and 500' ceiling in a single-engine recip airplane with the family on-board will make me hated by the hero-types.... but so be it..... I think it's poor-judgement as regards risk-management. I often fly "easy" IFR with venturiis and will keep them because they don't fail if I have airspeed. I have two Horizon gyros and one D.G., all vacuum-driven and they are wide-awake and operational before I get to 500' AGL. I"m not deliberately flying a S.E. airplane in hard IFR with less than a mile and 500' Ceilings (although I have "shot" a 1/2 mile approach in ice once in it when the forecast was missed. The venturiis never let me down. Ol' Gar can tell you about it.)

The best vacuum pumps are the "wet" pumps as far as reliablity goes, so if you insist on having one, I urge you to go that route and avoid the dry types.

An engine overhaul, if properly done, will cost you between $12K and $15K if you help. If you want to change from your present engine to the D-model O300... you can add another $4K to take care of the differences you'll encounter.

If you "down" your airplane and have all your ducks-in-a-row beforehand you can overhaul your present engine and be flying again in two weeks. If you change from one engine to the other you'll likely lose a couple days anyway.

Sorry for the hard-look at it, but hope it helps.

[n2582d]

...You would be converting from a cable pull start to an angled starter with a electric push button start, so those electrical mods would be necessary. Couple of hours labor and cost of wire, solenoid, push button or key switch. ...

Here’s an idea for those switching from the pull cable start yet want to maintain the original look of their panel. This comes courtesy of the Cessna 120-140 website. This Cole Hersee M486 momentary spring loaded switch must be pulled to close the contacts.

071EADB2-737B-41E6-9662-95C5312462A9.jpeg

(Additional p/n B5004-002).

[GAHorn]

Wrong knob-color to be "original", Gary.

[prairiechicken]

I would say, it's a total unknown as to the true state of your engine until it's torn apart. Well almost a total unknown as you say it had a newer top end but were those new cylinders at the top or reconditioned ? In my opinion, it's the cost of parts and part availability that's driving the cost of overhauls to levels which are hard to swallow. So, it's great your mechanic would include you in the work, so that you'll have a greater knowledge level, but likely your assistance won't vary the end dollar result that much.
There's also nothing to say this new to you 0-300D is any better than your present engine.

Thank you for the reply! There likely is nothing better about the O-300D that is accessible to me, other than it is an option to get parts sent off for inspection, new cylinders etc purchased, over a six month to a year timeline, meanwhile being able to fly with the current engine.

[prairiechicken]

Ty, If I'm not mistaken, I think you're also going from an 8-bolt prop to a 6-bolt one. Does the prop come with the engine?

Yes, a prop change would be required, and sadly, the prop has been reconditioned and sold already.

[prairiechicken]

Don't forget that $600 spinner changeout also.

Ty, at the risk of repeating myself...(I know no one present thinks I would do that tho'...

... Just what is it about a vacuum pump that makes you feel safer?
Is it the fact that NTSB and FAA accident reports find vacuum pump failures one of the most-common initiators of instrument-failure loss of control?

Is it because zero-zero takeoffs in a single-engined airplane are so much safer with a vacuum pump?

Is it that vacuum pumps don't ice-up when the rest of the airplane does?


Why anyone would deliberately take off in less than 1-mile and 500' ceiling in a single-engine recip airplane with the family on-board will make me hated by the hero-types.... but so be it..... I think it's poor-judgement as regards risk-management. I often fly "easy" IFR with venturiis and will keep them because they don't fail if I have airspeed. I have two Horizon gyros and one D.G., all vacuum-driven and they are wide-awake and operational before I get to 500' AGL. I"m not deliberately flying a S.E. airplane in hard IFR with less than a mile and 500' Ceilings (although I have "shot" a 1/2 mile approach in ice once in it when the forecast was missed. The venturiis never let me down. Ol' Gar can tell you about it.)



The best vacuum pumps are the "wet" pumps as far as reliablity goes, so if you insist on having one, I urge you to go that route and avoid the dry types.

An engine overhaul, if properly done, will cost you between $12K and $15K if you help. If you want to change from your present engine to the D-model O300... you can add another $4K to take care of the differences you'll encounter.

If you "down" your airplane and have all your ducks-in-a-row beforehand you can overhaul your present engine and be flying again in two weeks. If you change from one engine to the other you'll likely lose a couple days anyway.

Sorry for the hard-look at it, but hope it helps.

I wouldn't say "safer" is accurate, I was under the impression that newer gyros require more vacuum than my single little venturi can provide..That being said, I could install two larger venturies instead. I was only thinking I would kill two birds with one stone...

I am a green, low time pilot, with a pretty strong sense of self preservation. I don't intentionally test my own limitations, or the equipment's limitations, especially where weather is concerned, so a venturi setup with enough pull and volume to operate a D.G. and a horizon would suit me fine.

I'm not set on having an O300, it's just what is readily available. This one is owned by a friend who had a hangar failure total out his 172, and is right on the field, so no shipping. I consider this option partly to help him out. Another consideration is that my work schedule permits very little flying/tinkering time, so a (mostly) ready to install engine has it's upsides, to me anyway.

I appreciate the "hard look" approach!

[prairiechicken]

...You would be converting from a cable pull start to an angled starter with a electric push button start, so those electrical mods would be necessary. Couple of hours labor and cost of wire, solenoid, push button or key switch. ...

Here’s an idea for those switching from the pull cable start yet want to maintain the original look of their panel. This comes courtesy of the Cessna 120-140 website. This Cole Hersee M486 momentary spring loaded switch must be pulled to close the contacts.

071EADB2-737B-41E6-9662-95C5312462A9.jpeg

I like that! Having to modify the panel for push button start is a negative consideration for me. I don't want to permanently modify anything that I don't have to!

[prairiechicken]

Thank you everyone for the replies, I'm fairly new to aviation, but eager to learn all that I can!

A question on the starter: Is the starter adapter used on the O300D in any way more reliable, more robust, or better than the pull cable style found on the C-145? I have read that some are of the opinion that the pull type are less desirable, and the drive produces metal shavings, though I would suspect most of those problems may stem from mis-adjusted cables. The pull type appears more simple, at least in the electrical part.

Ty

[c170b53]

If you can come to an agreement on price based on crank and sump condition, it sounds like a win win situation for you and your friend. Two weeks for an overhaul sounds a bit aggressive to me, six months leaves enough time for socializing around your engine stand.

[4583C]

Ty
Some years ago I decided to switch from a C-145 to O-300-D and am happy with my decision. I had torn the C-145 down and sent the crank, cam and crankcase out to be recertified. The crankcase needed some cracks repaired as it had when overhauled years before and on further study of the engine logs the entire crankcase had been replaced early in the engines life (250 hours or so). I had a friend in the salvage business call me one day to ask if I still had the crankshaft and if I would sell it. He had a runout O-300-D he would sell and guarantee the crankshaft for little more than I got for the 8 bolt crank. I traded my prop and spinner for the one on the O300-D. The history of the crankcase was troubling to me and I felt it was a chance to get a newer and hopefully improved crankcase. My desire for a vacuum pump is about like George's, but going forward I felt the chances of finding a 6 bolt crank or prop would be easier and cheaper than the 8 bolt from the C-145.