Reliability of O-300

[Captain Wubba]

Hello. Looking at buying another airplane (I tried cutting out the
middleman and just flushing $100 bills down the toilet, but it isn't
quite the same). I'm currently considering early-mid 60s Cessna 172s,
powered by the 145 HP Continental O-300, and would like to hear from
any owners of these planes and engines. I have heard and read some
very mixed and inconsistent perspectives on these planes. One guy at
our airport who owns a straitback 172 says he has never had to have a
cylinder replaced or top overhaul done in 20 years of ownershop, and
has made it to TBO three times with no problem. Another guy I know (A
mechanic who I trust and respect) has told me that if I buy one of
these planes, I should expect to replace a cylinder every third
annual, and that I'll almost certainly need a top overhaul in the 1000
to 1200 hour range.

I have flown in these birds before, and was impressed by the
smoothness of the engine, compared to the O-320. But if anyone has
experience with these engines, I would greatly appreciate any help
with the following questions, and any general advice:

1. What kind of fuel burn do you consistently get with an O-300? Is
the generally reported 105 KIAS @ 8 GPH true?

2. Does the autogas STC help reduce the problem with valve sticking?
If you have the STC, do you generally burn a mix?

3.In general, has your experience led you to expect to have to do a
top overhaul about halfway through the TBO period? What are the
ballpark costs of such an operation.

4. In your opinion, would it be worth it to pay the premium to buy an
new 172 equipped with the O-320E2D?

5. Besides the valve guide and cylinder problems (often attributed to
running on 100 LL), are there any other major problems that would make
this an undesireable aircraft?

Thanks for the help,

Cap

[Rosspilot]

>
>1. What kind of fuel burn do you consistently get with an O-300? Is
>the generally reported 105 KIAS @ 8 GPH true?
>

yes.

>2. Does the autogas STC help reduce the problem with valve sticking?

never had valve sticking--flew the first 5 years (almost 600 hrs) NEVER using
autofuel STC, and for the last year, burning a 50/50 mix w/ 100LL and auto
(87). Still no valve problems.

>If you have the STC, do you generally burn a mix?
>

answered

>3.In general, has your experience led you to expect to have to do a
>top overhaul about halfway through the TBO period? What are the
>ballpark costs of such an operation.
>

Never had a top-overhaul since owning the plane.

>4. In your opinion, would it be worth it to pay the premium to buy an
>new 172 equipped with the O-320E2D?
>

You're talking apples/oranges. You call a difference of $100,000 a "premium"?

>5. Besides the valve guide and cylinder problems (often attributed to
>running on 100 LL), are there any other major problems that would make
>this an undesireable aircraft?
>
You seem to have your minnd convinced that the O-300 has valve problems . . . I
disagree with that premise.

If you are flying out of Lake Tahoe in August, or trying to tour the Grand
Canyon
in summer with passengers, or trying to cross the Rockies, it's a little
sluggish <G>
,



>
>
>
>
>
>


www.Rosspilot.com

[Captain Wubba]

(Rosspilot) wrote in message >...
> >
> >1. What kind of fuel burn do you consistently get with an O-300? Is
> >the generally reported 105 KIAS @ 8 GPH true?
> >
>
> yes.
>
> >2. Does the autogas STC help reduce the problem with valve sticking?
>
> never had valve sticking--flew the first 5 years (almost 600 hrs) NEVER using
> autofuel STC, and for the last year, burning a 50/50 mix w/ 100LL and auto
> (87). Still no valve problems.
>
> >If you have the STC, do you generally burn a mix?
> >
>
> answered
>
> >3.In general, has your experience led you to expect to have to do a
> >top overhaul about halfway through the TBO period? What are the
> >ballpark costs of such an operation.
> >
>
> Never had a top-overhaul since owning the plane.
>
> >4. In your opinion, would it be worth it to pay the premium to buy an
> >new 172 equipped with the O-320E2D?
> >
>
> You're talking apples/oranges. You call a difference of $100,000 a "premium"?

Sorry. My bad. Meant 'newer'. The premium for a O-320 equipped (3 or 4
year newer) 172 seems to be in the ballpark of $7000 to $10000.
>
> >5. Besides the valve guide and cylinder problems (often attributed to
> >running on 100 LL), are there any other major problems that would make
> >this an undesireable aircraft?
> >
> You seem to have your minnd convinced that the O-300 has valve problems . . . I
> disagree with that premise.
>
> If you are flying out of Lake Tahoe in August, or trying to tour the Grand
> Canyon
> in summer with passengers, or trying to cross the Rockies, it's a little
> sluggish <G>
> ,
>
>
>
> >
> >
> >
> >
> >
> >
>
>
> www.Rosspilot.com

[John Galban]

(Captain Wubba) wrote in message >...
Hi Cap,

I owned a '59 straight-tail with the O-300 as did my flying buddy.

>
> 1. What kind of fuel burn do you consistently get with an O-300? Is
> the generally reported 105 KIAS @ 8 GPH true?

That would be right on the money.
>
> 2. Does the autogas STC help reduce the problem with valve sticking?
> If you have the STC, do you generally burn a mix?

It did for me and my pal. We both experienced valve sticking when
burning 100LL. Using the rope trick to de-gunk a valve was almost an
annual occurence. Autogas made the problem go away. I used straight
autogas at home, but often had to mix with 100LL on XCs.
>
> 3.In general, has your experience led you to expect to have to do a
> top overhaul about halfway through the TBO period? What are the
> ballpark costs of such an operation.

Our experience was that the cylinders did not seem as robust as
their Lyc. counterparts, but that was back when overhauled cylinders
were commonly used and you had no idea how much TIS they had. Over a
3 1/2 year period (about 500 hrs.), I had one cracked cylinder and 1
with broken rings at around 1200 hrs. My friend had 3 cracked
cylinders between 900 and 1200 hrs.
>
> 4. In your opinion, would it be worth it to pay the premium to buy an
> new 172 equipped with the O-320E2D?

I expect you meant to say "newer" above, since new 172s are equipped
with IO-360s. I think it's a toss up. The O-320 Lyc. (particularly
the 80 octane version from '68 - '76) has a history of sticky valve
problems too. The real upside to the Lyc. is that it's a few thousand
$s cheaper to overhaul. It's not as smooth as the O-300.
>
> 5. Besides the valve guide and cylinder problems (often attributed to
> running on 100 LL), are there any other major problems that would make
> this an undesireable aircraft?

I think they are very desirable aircraft. The only drawback for me
was that I like to do a lot of backcountry flying. The 145 hp was a
little weak for high altitude mountain strips in the summer time.

Also, while it does not make the aircraft undesirable, the O-300 is
much more prone to carb icing that the Lyc. After you've been flying
behind one for awhile, recognizing and clearing carb ice becomes
routine.


John Galban=====>N4BQ (PA28-180)

[Dan Truesdell]

We were faced with an overhaul of the O-300 in our '64 172 (love the
manual flaps at 40 degrees!) After much debate, we came to the
conclusion that, while the engine is OK, one of the owners did have a
stuck valve that resulted in an engine failure. (He managed to restart
and limp back to the airport.) The O-300 is no longer made, so we opted
for the STC'd Lycoming O-360. Great choice! A bit more than the
overhaul (I think the total cost for the O-360 was about $32K), but you
get a factory new engine and prop, GREAT climb performance, a bit more
speed (~110 kts), and still books about 8 gph. Definitely a good move,
especially considering the original engine had a top overhaul at 1100
hours and had almost 2400 hours total when we replaced it.

Captain Wubba wrote:
> Hello. Looking at buying another airplane (I tried cutting out the
> middleman and just flushing $100 bills down the toilet, but it isn't
> quite the same). I'm currently considering early-mid 60s Cessna 172s,
> powered by the 145 HP Continental O-300, and would like to hear from
> any owners of these planes and engines. I have heard and read some
> very mixed and inconsistent perspectives on these planes. One guy at
> our airport who owns a straitback 172 says he has never had to have a
> cylinder replaced or top overhaul done in 20 years of ownershop, and
> has made it to TBO three times with no problem. Another guy I know (A
> mechanic who I trust and respect) has told me that if I buy one of
> these planes, I should expect to replace a cylinder every third
> annual, and that I'll almost certainly need a top overhaul in the 1000
> to 1200 hour range.
>
> I have flown in these birds before, and was impressed by the
> smoothness of the engine, compared to the O-320. But if anyone has
> experience with these engines, I would greatly appreciate any help
> with the following questions, and any general advice:
>
> 1. What kind of fuel burn do you consistently get with an O-300? Is
> the generally reported 105 KIAS @ 8 GPH true?
>
> 2. Does the autogas STC help reduce the problem with valve sticking?
> If you have the STC, do you generally burn a mix?
>
> 3.In general, has your experience led you to expect to have to do a
> top overhaul about halfway through the TBO period? What are the
> ballpark costs of such an operation.
>
> 4. In your opinion, would it be worth it to pay the premium to buy an
> new 172 equipped with the O-320E2D?
>
> 5. Besides the valve guide and cylinder problems (often attributed to
> running on 100 LL), are there any other major problems that would make
> this an undesireable aircraft?
>
> Thanks for the help,
>
> Cap


--
Remove "2PLANES" to reply.

[JFLEISC]

Several years ago I bought a '61 straight back for my wife and was shy about
the 0-300. Since then I've grown to love it. It does run smooth and all her
instructors rave about it. For some reason the plane is unusually quick also.
Climb is average.
>1. What kind of fuel burn do you consistently get with an O-300? Is
>the generally reported 105 KIAS @ 8 GPH true?
At 105 KIAS I actually think it's a little better, maybe 7GPH.
>
>2. Does the autogas STC help reduce the problem with valve sticking?
>If you have the STC, do you generally burn a mix?
Got the STC and been burning pure regular. It runs noticably better (and
considerably cheaper) but we are agressive about applying carb heat even though
I have never felt a trace of ice. The guy who sold it to me said it never saw
auto gas. Used a lot of oil so I took the top end apart. Only one valve was
slightly close to snug but 3 of 6 cylinders had one or more frozen rings from
carbon and goo. The cylinders mic-ed up within spec. (An A&P told me the older
cylinders were great but the new ones are too soft. How do I know?) Put new
rings on and now the engine is running sweet. This was the first thing done to
it in 1800 hours.
>
>3.In general, has your experience led you to expect to have to do a
>top overhaul about halfway through the TBO period? What are the
>ballpark costs of such an operation.
The ring job, 1 wrist pin, 2 valve guides and a gasket set cost me a tick over
$400.
>
>4. In your opinion, would it be worth it to pay the premium to buy an
>new 172 equipped with the O-320E2D?
My biggest bitch is that those Continentals seem impossible to stop from
leaking oil. The Lyc. in my other plane is always dry.
>
>5. Besides the valve guide and cylinder problems (often attributed to
>running on 100 LL), are there any other major problems that would make
>this an undesireable aircraft?
>
>Thanks for the help,
>
>Cap


Jim

[jls]

"JFLEISC" > wrote in message
...
> Several years ago I bought a '61 straight back for my wife and was shy
about
> the 0-300. Since then I've grown to love it. It does run smooth and all
her
> instructors rave about it. For some reason the plane is unusually quick
also.
> Climb is average.
> >1. What kind of fuel burn do you consistently get with an O-300? Is
> >the generally reported 105 KIAS @ 8 GPH true?
> At 105 KIAS I actually think it's a little better, maybe 7GPH.
> >
> >2. Does the autogas STC help reduce the problem with valve sticking?
> >If you have the STC, do you generally burn a mix?
> Got the STC and been burning pure regular. It runs noticably better (and
> considerably cheaper) but we are agressive about applying carb heat even
though
> I have never felt a trace of ice. The guy who sold it to me said it never
saw
> auto gas. Used a lot of oil so I took the top end apart. Only one valve
was
> slightly close to snug but 3 of 6 cylinders had one or more frozen rings
from
> carbon and goo. The cylinders mic-ed up within spec. (An A&P told me the
older
> cylinders were great but the new ones are too soft. How do I know?) Put
new
> rings on and now the engine is running sweet. This was the first thing
done to
> it in 1800 hours.
> >
> >3.In general, has your experience led you to expect to have to do a
> >top overhaul about halfway through the TBO period? What are the
> >ballpark costs of such an operation.
> The ring job, 1 wrist pin, 2 valve guides and a gasket set cost me a tick
over
> $400.
> >
> >4. In your opinion, would it be worth it to pay the premium to buy an
> >new 172 equipped with the O-320E2D?
> My biggest bitch is that those Continentals seem impossible to stop from
> leaking oil. The Lyc. in my other plane is always dry.

Some leak, some don't. Most do but not much. I am flying a friend's 172
at the time which is just absolutely a joyful experience. It's a '56 172
with the straight tail and that great Johnson bar between the seats. It
gets off and climbs with a vengeance and the O-300 runs wonderfully. Great
sound too and smoooooth. A 4-banger Lycoming never ran this smooth. My
first experience with an O-300 was in a ragwing 170, and I was instantly in
love.

I'm restoring another 172 which I have flown too, O-300 engine also, but
this one is a '66 and needs cylinders. So what? You can buy cylinder
kits today for half what you could buy them for ten years ago, thanks to
competition among TCM, ECI, and Superior. The cylinders don't always last
to TBO but the bottom end is very durable and solid. I know of a trusty
O-300 in an old 172 nearby with over 2300 hours on the bottom end and still
running strong. He's busted TBO by over 500 hours.

To extend the life of the cylinders I would lean carefully and monitor cht
and egt religiously. Change oil every 25 hours. And make power changes
smoothly, gradually. I'd also watch the baffling, avoid 100LL except as a
mix of 10% avgas and 90% mogas because the low-compression engine is not
designed for high-leaded, hi-octane gas like 100LL. Fly regularly and no
cold starts below freezing temperatures. A good oil filter is a must. I'd
also use an additive to leech out lead fouling and carbon deposits and keep
the plugs cleaned and gapped. Watch your mag timing. I firmly believe
that MMO and Alcor TCP are helpful (one or the other), especially in the
O-300 using avgas, to keep valves from sticking. Read more about these
great engines in the 172 forum in Yahoogroups. The current discussion is
about MMO and its obvious benefits. I don't need graphs, charts,
engineering reports and so-called hard data and statistical studies to
convince me MMO is desirable. And, btw, I put a capful of MMO in my
Harley's tank every fillup back in the 70's as advised by H-D Motor Company.

And finally, if you haven't flown Continental's six bangers, including the
O-300 and its grandbaby, the IO-360, you just THINK you've flown an
aircraft.

[Rosspilot]

> The current discussion is
>about MMO and its obvious benefits.

Can you suggest how much MMO should go into the engine and how much should go
into the fuel?


www.Rosspilot.com

[jls]

"Rosspilot" > wrote in message
...
> > The current discussion is
> >about MMO and its obvious benefits.
>
> Can you suggest how much MMO should go into the engine and how much should
go
> into the fuel?
>
>
> www.Rosspilot.com
>

Rosspilot, I use it sparingly, about 2 oz. per 24 gallon fillup, and in the
fuel tanks only. It wouldn't hurt to put an ounce or two in your oil, but
I never saw the need to.

[Rosspilot]

>I use it sparingly, about 2 oz. per 24 gallon fillup, and in the
>fuel tanks only.

Thanks . . . I put some in my fuel tanks when I started using auto gas, and
started to see gray streaks along the right side of the engine
cowling--apparently coming from the exhaust. It wiped right off, but I didn't
know what it was. When I stopped using MMO, the streaking also stopped. Maybe
I used too much . . . any ideas what the gray streaks were?


www.Rosspilot.com

[Brett Justus]

I have a '65 172 and love the O-300. When I first got it I had
problems with plug fowling (despite leaning on the ground, etc.) and
had a valve stick HARD. The previous owners had fed it a steady diet
of 100LL. I started using mostly auto gas and the problems have
gradually gone away. The engine was rebuilt with new Millennium
cylinders and to new tolerances in 99 and had 1050 hours when I bought
the plane a year ago. One cylinder had been replaced at about 600
hours due to valve problems. I flew a little over 100 hours in the
first year and compressions were all in the 70s when I had the annual
done last month. They key, like with any engine is to fly it
frequently.


>
> 1. What kind of fuel burn do you consistently get with an O-300? Is
> the generally reported 105 KIAS @ 8 GPH true?

I plan 9 GPH block to be on the safe side.


> 2. Does the autogas STC help reduce the problem with valve sticking?


ABSOLUTELY -- so does flying frequently and using Marvel's Mystery
Oil.


> 3.In general, has your experience led you to expect to have to do a
> top overhaul about halfway through the TBO period? What are the
> ballpark costs of such an operation.

1200 HRS SMOH -- Compressions in the 70s, engine runs great, uses very
little oil -- (about 1 Qt per 15-18 hrs.)

>
> 4. In your opinion, would it be worth it to pay the premium to buy an
> new 172 equipped with the O-320E2D?

No, but they're great planes too. I bought a 172 with the Continental
specifically because they are such good bargains. But you have to be
careful to get the right one. The Millennium cylinders and regular
use since overhaul were factors I considered in purchasing this one.

>
> 5. Besides the valve guide and cylinder problems (often attributed to
> running on 100 LL), are there any other major problems that would make
> this an undesireable aircraft?

The older 172s have narrower gear, lighter weight and slightly
different handling due to cuffed wings on the later models, etc. All
this makes them a little more challenging in winds, but still a
wonderful airplane. Like others have said, carb ice is a definite
issue, be proactive about checking for it and using carb ht when
necessary. Remember to apply carb heat right before takeoff if you've
been idling a long time; even if you already checked carb heat earlier
during your run-up.

- Brett

[Jim Weir]

(Brett Justus)
shared these priceless pearls of wisdom:

->I have a '65 172 and love the O-300. When I first got it I had
->problems with plug fowling

How did the chickens get in to the engine in the first place?



->
->ABSOLUTELY -- ... and using Marvel's Mystery
->Oil.

Certainly not in a CERTIFICATED aircraft. Merciful heavens to Betsy {;-)


Jim




->



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Ron Natalie]

"Rosspilot" > wrote in message ...

>
> >4. In your opinion, would it be worth it to pay the premium to buy an
> >new 172 equipped with the O-320E2D?
> >
>
> You're talking apples/oranges. You call a difference of $100,000 a "premium"?

I think he just meant a later model. The "NEW" 172's don't have O-320's, they
have IO-360's.

[Brett Justus]

Jim Weir > wrote in message >...
> (Brett Justus)
> shared these priceless pearls of wisdom:
>
> ->I have a '65 172 and love the O-300. When I first got it I had
> ->problems with plug fowling
>
> How did the chickens get in to the engine in the first place?

HEY spell check says that word is just fine! (WoooOOOPS)


> ->ABSOLUTELY -- ... and using Marvel's Mystery
> ->Oil.


Somebody else must have used my computer when I was away -- I would never do that.




> Certainly not in a CERTIFICATED aircraft. Merciful heavens to Betsy {;-)
>
>
> Jim