Nose Cowl cracks with 0-360

[Plummit]

Hi all. In looking at various 170s with the Lycoming 0-360, I came across one that had patches on the lower part of the cowl. The owner told me that the patches were to cover cracks caused by the 0-360. Is this a common problem with 0-360 equiped 170s?

regards

~Marc

[Dave Clark]

I don't think it's a common problem. The lower cowl would probably have patches over the original exhaust pipe outlets. N8018A with the Avcon conversion used a fiberglass nose bowl.

Proper fit and minimizing stress areas is essential. That's also true with stock engines. I've seen a lot of old cowls on stock engines that were cracked also.

[c170b53]

There're lots of patches found around the intake scoop. That part is almost impossible to find and when found commands big dollars.

[GAHorn]

This will not be poplular with those who have converted to the engine, but.... One of the disadvantages to the Lycoming O-360 four-banger is vibration and cowling cracks. Windshields too. And higher incidence of avionics failures.
Stuffing more horsepower into fewer cylinders is part of the problem. A rigid engine mount is another. The three Lycoming conversions I've flown absolutely scared me upon start-up and shut-down with all the shaking goin' on. The performance sure is nice tho', once it's up and running.
(The TCM IO-360 has it's own disadvantages as well, but the smoothness of that 6-cylinder, and the even greater horsepower, along with less cowling modifications and the fact that I hate fiberglass on classic airplanes is what has me convinced it's the conversion I'll do if ever I do.)

[170C]

I agree with George regarding the shaking that the Lycoming O-360's do to an airframe. I am always hearing that those LYC's are bullet proof engines and I can't dispute it as I have never owned one. They have a nice 2000 hr tbo and there are tons of them around for parts, replacements, etc. BUT, as he says, there's nothing with 4 cylinders that is as smooth as those 6 cylinder Continentals even though they have lower tbo's (1500 I think for the IO-360). I keep hearing folks say that the IO-360's (Cont) has a lot of problems, but I don't know what they really are. I also don't know what the differences are in the IO-360's like the C-337's used vs the more modern ones some Mooney's and others use. If I had the wherewithall to do so (and wasn't going to move up to a C-180) I would sure give serious consideration to the Continental Conversion on my "C" model.

[Roesbery]

Been flying the Lyc o-360 powered 170B for over 20 years. Have not had any cracking from vibration. Did a dynamic prop balance many years ago and made it real smooth. My current magic carpet is fine as is, with over 1800 hours with good compression, just likes lots of oil.

[Dave Clark]

The only bad shaking I've noticed is if you have a fouled plug or bad cylinder. If you loose performance on one of four cylinders it shakes a lot more than loosing one of six. In cruise, where you spend most of your time, a good condition, properly installed Lyc is pretty smooth.

[or170B]

It sure seems strange to me that all the complaining about shakey Lycs. comes from people that don't have one in their plane. I am on my third 170 and my second one with Lyc. power. And besides initial start when cold the viberation difference is hardly noticed. However the increase of perfomance is indisputable. This engine makes a 170 into a true High altitude and short field performer.

[Bruce Fenstermacher]

If I could afford it any additional vibration would not stop me from installing a Lycoming 0-360 in my 170. I base this on about 100 hours of riding around in a 170 with one installed and a few hundred hours in Cherokees with essentially the same engine installation.

[GAHorn]

[quote="or170B"]It sure seems strange to me that all the complaining about shakey Lycs. comes from people that don't have one in their plane. .../quote]

Having flown 'em, is one reason.

[c170b53]

Is the late 170 nose bowl is .025 or .032 ? It looks like alot of cracking due to fatigue.

[GAHorn]

In all fairness, even the original C-145/O-300 eventually will develop a crack or two (or three) in the metal nose bowl after 50 years or so. Usually the fix is to stop drill it, add a doubler, and/or backfill it with epoxy and wire. (The rolled edges of the cowl openings are not noted for being crack-free. The typical repair is a stop-drill, fill with epoxy over a wire such as a coat-hanger that's been epoxied into the backside of the rolled edge to stiffen it up.)
Anyway, the Lyc does shake a bit (or a lot depending upon who you talk to) most noticeably on startup and shutdown. When the engine was installed in the 172's beginning in the mid-sixties, the engine-mounts (Lord types) used were large, soft, and absorbed a lot of this. The 170 conversion isn't quite so soft an installation, but it's a sound conversion with pleasing performance. The nose bowl is typically converted to fiberglass and there are side-blisters as well to accomodate the front rocker-boxes of the wide-deck Lyc. Bad news: Its a matter of time and the fiberglass will develop cracks. Good news: Fiberglass is repairable.
The TCM IO-360 is a 6-cylinder and runs smoother, puts out just a bit more hp, and requires no noticeable, external modifications to the cowling. Drawback, is it requires fuel system modifications. The TBO differences between the engines is not significant, in my opinion, if you're buying a low-to-midtime engine. Neither engine's cylinders will get to TBO without a "hot section" ("top" overhaul), and both of them have rugged, dependable lower ends that will go beyond their recommended TBO's.
If you want a 170 with striking performance, get one with either a Lyc O-360 or TCM IO-360 conversion. If you like original classics, and don't try to get it out of a 800-foot strip or over a 14K-foot mountain at gross wt, ... the original engines do just fine, are extremely dependable, can be worked on just about anywhere, and sip the gas.

[Plummit]

In all fairness, even the original C-145/O-300 eventually will develop a crack or two (or three) in the metal nose bowl after 50 years or so. Usually the fix is to stop drill it, add a doubler, and/or backfill it with epoxy and wire. (The rolled edges of the cowl openings are not noted for being crack-free. The typical repair is a stop-drill, fill with epoxy over a wire such as a coat-hanger that's been epoxied into the backside of the rolled edge to stiffen it up.)
Anyway, the Lyc does shake a bit (or a lot depending upon who you talk to) most noticeably on startup and shutdown. When the engine was installed in the 172's beginning in the mid-sixties, the engine-mounts (Lord types) used were large, soft, and absorbed a lot of this. The 170 conversion isn't quite so soft an installation, but it's a sound conversion with pleasing performance. The nose bowl is typically converted to fiberglass and there are side-blisters as well to accomodate the front rocker-boxes of the wide-deck Lyc. Bad news: Its a matter of time and the fiberglass will develop cracks. Good news: Fiberglass is repairable.
The TCM IO-360 is a 6-cylinder and runs smoother, puts out just a bit more hp, and requires no noticeable, external modifications to the cowling. Drawback, is it requires fuel system modifications. The TBO differences between the engines is not significant, in my opinion, if you're buying a low-to-midtime engine. Neither engine's cylinders will get to TBO without a "hot section" ("top" overhaul), and both of them have rugged, dependable lower ends that will go beyond their recommended TBO's.
If you want a 170 with striking performance, get one with either a Lyc O-360 or TCM IO-360 conversion. If you like original classics, and don't try to get it out of a 800-foot strip or over a 14K-foot mountain at gross wt, ... the original engines do just fine, are extremely dependable, can be worked on just about anywhere, and sip the gas.

Thanks George, that's a wealth of info and worth every penny I paid for membership. I'm still looking for the right 170 to buy and I feel I'd be happy with either the Lyc or TCM, but with all else being equal, I think I'd prefer the 6 cyl.

regards

~Marc

[Joe Moilanen]

800' strip? I'm getting out of my 650' strip with the 145 hp (8043 prop though). When mine reaches TBO I'm going for the 0-360 Lycoming. As far as not making it to TBO without a "top", I've seen a lot of 0-360's go to TBO or 2400 hour without a TOH. If any engine can do it, its the 0-320 or 0-360. About as bullet proof as they come. With a dynamic prop balance, the woes of vibration cracking should be mute.

Joe

[Dave Clark]

In all fairness, even the original C-145/O-300 eventually will develop a crack or two (or three) in the metal nose bowl after 50 years or so. Usually the fix is to stop drill it, add a doubler, and/or backfill it with epoxy and wire. (The rolled edges of the cowl openings are not noted for being crack-free. The typical repair is a stop-drill, fill with epoxy over a wire such as a coat-hanger that's been epoxied into the backside of the rolled edge to stiffen it up.)
Anyway, the Lyc does shake a bit (or a lot depending upon who you talk to) most noticeably on startup and shutdown. When the engine was installed in the 172's beginning in the mid-sixties, the engine-mounts (Lord types) used were large, soft, and absorbed a lot of this. The 170 conversion isn't quite so soft an installation, but it's a sound conversion with pleasing performance. The nose bowl is typically converted to fiberglass and there are side-blisters as well to accomodate the front rocker-boxes of the wide-deck Lyc. Bad news: Its a matter of time and the fiberglass will develop cracks. Good news: Fiberglass is repairable.
The TCM IO-360 is a 6-cylinder and runs smoother, puts out just a bit more hp, and requires no noticeable, external modifications to the cowling. Drawback, is it requires fuel system modifications. The TBO differences between the engines is not significant, in my opinion, if you're buying a low-to-midtime engine. Neither engine's cylinders will get to TBO without a "hot section" ("top" overhaul), and both of them have rugged, dependable lower ends that will go beyond their recommended TBO's.
If you want a 170 with striking performance, get one with either a Lyc O-360 or TCM IO-360 conversion. If you like original classics, and don't try to get it out of a 800-foot strip or over a 14K-foot mountain at gross wt, ... the original engines do just fine, are extremely dependable, can be worked on just about anywhere, and sip the gas.

George thanks for giving the Lycoming some credit at least

All the STC conversions I'm aware of use the Dynafocal mount with Lord mounts so your "The 170 conversion isn't quite so soft an installation, " doesn't quite make sense.