Carbon & Exhaust Valve

[PA1195]

Re: Carbon & Exhaust Valve

Gary, I have been running Phillips XC20W50 per recommendation of my AI. A few years ago I had a C150 with a C200 and used Aeroshell 100 in summer and 80 in winter. I'm having trouble wrapping my head around the Phillips same weight for winter and summer, maybe I'm just old school and ignorant? Saveral have mentioned leaning. Since my Tcraft and most do not have a mixture control I assume you mean you adjust the mixture at the carburetor twice a year?

Thanks,

Darrin

Hi Darrin and thanks for the comments re oil. My experience with that oil is limited but ok. I have seen the oil pressure fall off after ~20 hrs use, and assume it's due to shearing in the accessory case (gears/pump), some loss of viscosity improver effectiveness, and possible dilution with combustion byproducts or fuel over time. If you like by all means it use it. Monitor your spark plugs and exhaust for soot in case it tends to burn some oil more than a single viscosity 'might'. It's a 20W oil that thins but not as much as a single grade at high temps due to additives.

I have a Marvel carb and lean to peak rpm whenever on the ground. Dropoff at mixture cut is ~25rpm and I adjust the idle mixture seasonally...out 1/2 turn in the winter; in the same during the summer.

Marvel carbs usually have an accelerator pump that ads additional fuel when the throttle is quickly opened, Strombergs don't (or at least those I had didn't). Using carb heat when opening the throttle will richen the air fuel mixture via less dense heated air being ingested and may minimize stumbles.

Gary

[dkenney1]

Re: Carbon & Exhaust Valve

Darrin,

Depending upon the carb they have on their particular engine they may be able to lean like 'conventional' engines. The Stromberg NS-A3A1 on most of these A-65's can have a mixture control, but it does not become really effective until over 5,000 feet. Most are wired in place. Search on here for much more information regarding the Stromberg's mixture 'quirks'. You cannot lean on the ground with this model of Stromberg, it will just kill the engine as you try to apply throttle.

I have a C85-8, I can't remember what the AI said the carb was but i don't think it was Stromberg. I'm looking through the vast materials from the engine overhaul. When it gets cooler like 40 or below, if I advance the throttle quickly it spits and sputters, but have not had it quit as the TCM memo describes. I have not made the plate that covers the air filter, maybe that would help. To prep for the cooler weather I need to located a oil tank blanket/cover that I guess stays on for flight as well. I checked aircraft spruce and wag-aero so far nothing. Come spring for next oil change I think I will try AeroShell 100 and see how that goes.

Thanks

[M Towsley]

Re: Carbon & Exhaust Valve

The blanket that Wag makes is too big for the 4 quart tank, it is made for a larger tank. It does not fit the 4 quart well. I have never seen the air filter plate installed on a plane, doesn't mean someone hasn't, though. I fly when it is very cold with no problems. I just follow the TCM guidelines for keeping the engine clear when throttled back and I don't apply throttle super-fast, either.

Here is the cold weather ops pdf thread that you may remember, here is the thread: http://vb.taylorcraft.org/showthread...ental+bulletin

[MontanaT-craft]

Re: Carbon & Exhaust Valve

The following is an article by Mike Bush that was published in 1998. I found the "Lie no. 3" about oil to be particularly interesting. I have decided to go to straight weight oil based on what is stated there. The whole article is long, but I think worthwhile.
Charles
MIKE BUSCH

http://www.avweb.com/news/maint/182849-1.html

This article originally appeared in the March 1998 issue of CESSNA PILOTS ASSOCIATION MAGAZINE. | June 6, 1998

Lie #1:
Lycoming engines are better than Continental engines.
(Or vice-versa.)

MaintenanceI bought my first airplane 30 years ago. It was a Cessna 182 powered by a Continental O-470-R engine. Since then I've owned a succession of airplanes, and each one-quite coincidentally-was powered by a big-bore Continental. My engines have always made TBO and been relatively trouble-free. So it's not surprising that I'm something of a fan when it comes to TCM engines.

It's equally unsurprising that at least half the pilots and aircraft owners I meet are Lycoming bigots. They brashly state "I'd never own a Continental-powered airplane!" If you ask why, they'll tell you a series of anecdotal episodes about how their Lycoming-powered Turbo Saratoga made it to 1,000 hours past TBO, while their best friend wound up having to tear down the TCM factory reman in his Mooney 231 or Beech B36TC after just 475 hours.

TCM Wings
Powered by Lycoming
Let's set the record straight. Lycoming and TCM engines are very similar designs using very similar technology and metallurgy. Both are horizontally-opposed air-cooled designs with bolt-together aluminum case halves and bolt-on cylinders with sandcast aluminum heads screwed onto nitrided steel barrels. Both use fixed-timed dual magneto ignition systems, and valve trains with overhead rocker arms, shrouded hollow pushrods, and hydraulic valve lifters. Both use similar compression ratios, similar RPM red-lines, and similar power-to-displacement ratios. And both have comparable records of reliability and longevity.

Certain problems tend to occur more frequently in one brand or the other. Continentals have a lot more crankcase cracks, head-to-barrel separations, and premature valve guide wear problems than Lycomings. On the other hand, Lycomings suffer stuck and broken valves and spalled cams and lifters much more often Continentals.

Some TCM and Lycoming models have better track records than other TCM and Lycoming models. For example, the TCM TSIO-360 series (used in Mooneys, Skymasters, and various other aircraft) tend to be more troublesome and maintenance-intensive than other Continentals. Likewise, the Lycoming O-320-H2AD engine has had a dismal history of cam and lifter problems when flown irregularly and operated in cold climates.

But while certain specific TCM and Lycoming models are problem-prone, it is simply wrong to make a general assertion that engines of either manufacturer are more reliable than those of the other. It's just not so.

Lie #2:
Turbocharged engines are troublesome, inefficient and costly.

Continental engineWhen I learned to fly on the East Coast thirty-something years ago, turbocharging was a dirty word. Everybody said turbos were expensive, inefficient, maintenance-intensive, and problem-prone; it shortens TBO and increases operating cost drastically, and makes no sense unless you live in the mountains. Or so everybody said.

Well, everybody was wrong. I've owned, operated and maintained a turbocharged twin Cessna for the past eleven years. It's proven to be the most reliable airplane I've ever owned: reliable, efficient, and almost completely trouble-free. Both engines made it to 500 hours past TBO without ever having a cylinder off, and when they were finally majored, they turned out to be in great shape.

Most of the anti-turbocharging arguments you hear are bunk. For example, take the claim that turbocharged engines are inefficient. Now, it's true that most turbocharged engines have a lower compression ratio than their normally-aspirated counterparts (typically 6.5-to-1 vs. 7.5-to-1), and that the turbo will burn a bit more fuel at any given power setting. But specific fuel consumption is only part of the story. The other part is that airframes are much more efficient up at the higher altitudes that turbocharging allows.

For instance, by climbing from 6,000' to 12,000' and throttling back from 75% to 65% power, my Turbo 310 can fly 5 knots faster than a normally-aspirated 310, and do it at lower fuel flow. If I'm willing to use oxygen and climb to FL200, I can beat the non-turboed 310 by 25 knots with no fuel flow penalty. The normally-aspirated airplane is more efficient than the turbo only if you force both airplanes to fly at the same low altitude, and that's not a meaningful comparison.

How about the claim that turbocharged engines are much more expensive to operate and maintain? It's true that turbos are more vulnerable to abuse in the hands of a ham-fisted pilot. If your airplane is used for training or rental use and flown by lots of pilots, you probably don't want a turbo. But barring such abuse, my worst-case analysis indicates that a 300 hp turbocharged engine should cost no more than $10/hour more to operate than its normally-aspirated sibling. When you consider that the sort of aircraft that use such engines — Bonanzas, Centurions, Saratogas, etc. — typically cost $100 to $150/hour to fly, you can see that the difference is chump change

Lie #3:
Modern multi-viscosity oil offers superior lubrication and longer engine life than old-fashioned single-weight oil.

During the 70s and 80s, there was a dramatic shift from single-weight to multi-viscosity oils by operators of general aviation aircraft...due in large measure to very effective advertising campaigns by Shell and Mobil that touted their multi-vis products (Aeroshell 15W50 and Mobil AV 1) as the greatest aeronautical innovation since the nosewheel.

During the same 20-year period, there was a dramatic increase in premature engine problems in the owner-flown G.A. fleet. It was not a coincidence.

In contrast to "working airplanes" that fly almost every day, most owner-flown airplanes spend most of their lives in the chocks. The biggest enemy of their engines is not inadequate lubrication. It's rust.

Multi-vis oil simply does not provide as effective protection against rust as single-weight oil. The defining characteristic of multi-viscosity oil — the fact that it doesn't thicken up at cool temperatures — makes it a lousy corrosion inhibitor. During periods of disuse, multi-vis oil strips off cylinder walls and cam lobes much more readily than does thick single-weight oil, leaving those parts vulnerable to corrosion, followed by spalling and eventually destruction.

But what about the superior lubricating properties of multi-vis oil? Basically bunk!

It turns out that multi-vis oil is not a better lubricant than single-grade oil. It's actually a bit worse. The reason is that multi-vis oil is made by starting with a thin, single-weight oil stock and adding man-made polymers called "Viscosity Index improvers" that increase viscosity as temperature increases. However, such VI improvers are not lubricants, and their addition actually displaces a certain amount of lubricating base stock (on the order of 10%). In other words, there's more "oil" in a quart of single-weight oil than in a quart of multi-vis.

Now this is no big deal, since the lubrication demands of most piston aircraft engines are rather modest (compared to automobile engines, for example). What is a big deal is the fact that single-weight oil does a better job of protecting engines against rust during period of disuse. That's why we've long recommend single-weight oil for any engine that doesn't fly at least once a week.

Fortunately, after two decades of multi-vis mania, it now appears that more and more G.A. operators are starting to recognize the shortcomings of multi-vis oil and are switching back to single-weight. An increasing number of top-rated overhaul shops are now recommending the use of single-weight oil.

Lie #4:
If you can't fly regularly, at least be sure to turn over the prop by hand every week or two to redistribute the oil.

Now there's a really dumb idea! I wonder who first came up with it?

Engines that don't fly regularly are vulnerable to rust because the oil film that protects their steel parts from corrosion begins to strip off after a week or two. Gravity is the culprit — oil flows from top to bottom — and so the areas at greatest risk are the tops of cylinder bores, the tops of cam lobes, and so forth.

Now suppose you turn over the prop by hand. Does this "redistribute the oil?" Sure it does! It scrapes oil off the top of the cylinders and accelerates its flow downhill. The same is true of cam lobes and lifters.

Now I realize full well that at least one of the engine manufacturers recommends turning over the prop by hand periodically in its "flyable storage" recommendations. I still maintain, however, that the only way to replenish the protective oil film is to fling large quantities of oil around the innards of your engine with great vigor. And the only way to do that is to run the engine at high RPM...preferably by flying the airplane attached to it. Turning over the prop by hand just won't cut it.

Lie #5:
The less oil an engine burns, the better.

Get a few aircraft owners get together over a few beers, and inevitably the conversation turns to oil consumption. "I'm only using a quart in 30 hours," one will say. "That's nothing," brags another owner, "I don't have to add any make-up oil between 50-hour oil changes!" The owners doing this bragging probably don't realize that they probably won't make it to TBO without a costly mid-term top overhaul! It turns out that ultra-low oil consumption is often a bad omen when it comes to cylinder longevity.

For a cylinder to make it to TBO, it must be protected from metal-to-metal scuffing by the piston rings. This protection comes from a film of oil that coats the cylinder barrel and causes the rings to "hydroplane" instead of scuffing the barrel.

Now, if the cylinder barrel is properly coated with oil, it's inevitable that some of this oil will be burned up in the combustion process. That's why a certain amount of oil consumption is perfectly normal.

Ultra-low oil consumption indicates one of two things: either the oil film is too thin, or the oil is not reaching the critical upper portions of the cylinder walls where the compression rings reverse direction at top-dead-center (the so-called "ring-step area"). Without adequate lubrication, there's a high risk of metal-to-metal contact between the compression rings and the cylinder wall.

Experience seems to indicate that oil consumption lower than about a quart in 20 hours may not bode well for long cylinder life. Barrel wear in the ring-step area becomes likely, leading to rapidly deteriorating compression and accelerating oil consumption at 500-1000 hours.

While low oil consumption has always been acknowledged as a sign of a tight, well-broken-in engine, there is strong evidence that a quart in 30 or 40 hours may well be too much of a good thing.

Lie #6:
The cooler the engine's oil and cylinder head temperatures, the better.

It turns out that the "cooler is better" notion isn't quite right. While excessively high temperatures are bad for your engine, low temperatures are no great shakes, either.

Oil coolerTake oil temperatures. Most of our airplanes have oil temperature gauges that have a green arc running from 75°F to 240°F, with a red-line at 240°F. Now, 240°F is way hotter than we'd like to see. Keep in mind that the oil temperature probe is usually located at the place in the oil system where the oil is coolest, often near the outlet of the oil cooler. So if the gauge reads 240°F, the oil is probably hitting close to 280°F at the hottest point in its circuit through the engine. That's hot enough to cause petroleum-based oil to oxidize and break down at an accelerated rate. We've either got to bring down the oil temps, or change the oil very frequently.

On the other hand, oil temperatures lower than 170°F or so on the gauge present a different problem...namely, that the oil is probably not reaching the boiling point of water at the hottest point in its travel. Why is this important? Every time we shut down the engine, a slug of water condenses inside the cooling engine and runs down into the oil sump. If we don't get rid of this water the next time we fly, there will be a progressive water build-up inside the engine. That water will mix with the sulfur and nitrogen byproducts of combustion to form sulfuric and nitric acid. And that will start eating away at the innards of our engine. The solution is to make sure the oil gets hot enough to boil off the entrapped water, so that the resulting steam passes harmlessly out the breather.

Oil temperatures of 180°F to 200°F on the gauge are hot enough to get rid of this water, yet cool enough not to accelerate the breakdown of the oil. So that's ideally where we'd like to see our oil temperature gauge in-flight.

Cylinder cooling systemWhat about cylinder head temperatures? The CHT gauge on a TCM engine usually has a green arc from 200°F to 460°F, with a red-line at 460°F. Lycomings generally have a CHT red-line of 500°F. Once again, red-line CHT is way too hot for optimum engine longevity. At those temperatures, the aluminum cylinder heads are vulnerable to cracking, and the exhaust valve guides are vulnerable to accelerated wear.

On the other hand, CHTs below about 300°F create another problem: lead fouling. Our engines operate on avgas that contains large amounts of tetraethyl lead (TEL). Even so-called "100LL" contains enough TEL to keep the EPA awake at night. The purpose of TEL is to enhance the octane (detonation resistance) of the fuel. Unfortunately, it also can cause lead deposits in the engine, particularly on spark plug electrodes and in piston ring grooves.

To prevent such lead fouling, avgas contains a "lead scavenging agent" called ethylene dibromide, whose job it is to dissolve excess lead and let it pass harmlessly out the exhaust pipe. However, ethylene dibromide doesn't do its scavenging job unless combustion temperatures are fairly high. That's why lead fouling problems tend to emerge when CHTs are below about 300°F.

Ideally, we should try to keep CHTs in the 350°F to 400°F range as much as possible. That's cool enough to keep the cylinder heads and valve guides happy, but hot enough for effective lead scavenging.

Lie #7:
Aggressive leaning results in burned valves and detonation.

Fear of the red knob is one of the most pernicious areas of misinformation among general aviation pilots. Most pilots operate way too rich most of the time, and do so because of the mistaken belief that leaning will harm their engine. The result is usually trouble: fouled spark plugs, accelerated exhaust valve guide wear, and stuck exhaust valves.

Lycoming engineLycoming has long authorized leaning to peak EGT at any cruise setting up to 75% power. TCM authorizes leaning to peak EGT up to 65%, and its latest recommendations even endorse lean-of-peak operation for many big-bore engines, provided the engines will run smoothly when operated that lean.

Contrary to popular belief, aggressive leaning doesn't cause burned valves. Most burned valves are the result of excessive valve guide wear or valve stem contamination.

Aggressive leaning doesn't cause detonation, either. Most of our engines are incapable of detonation at cruise power settings, provided that we don't exceed CHT red-line or try to burn contaminated fuel. Furthermore, recent tests on Lycoming engines by ASTM revealed this fascinating result: detonation is most likely to occur at a mixture setting 11% richer than stoichiometric (i.e., substantially richer than peak EGT).

Lean as aggressively as the book allows. For Lycomings, that means peak EGT at all cruise power settings to 75%. For Continentals, lean to peak EGT up to 65%, 50°F rich of peak at 75%. For turbocharged engines, also limit TIT to 1600°F.

Lean during all ground operations except for engine start. It is particularly important to lean for taxi and runup. Since EGT is usually off-scale at idle power, the best method is to lean for peak RPM at idle.

Lie #8:
It's bad to cruise at high manifold pressure and low RPM ("oversquare").

The old saw about never allowing MP to exceed RPM/100 is bunk! Fortunately, this one seems finally to be moving toward a well-deserved death, after decades of being accepted as Gospel by countless well-intentioned pilots.

TCM and Lycoming authorize cruise operation at 1 to 3 inches "oversquare" for most normally-aspirated engines, and allows 9 to 12 inches "oversquare" for most turbocharged engines. Check the cruise charts in your POH or, better yet, obtain the operator's manual for your engine.

Operating at minimum RPM and maximum MP (within the allowable envelope) actually helps your engine last longer. Low RPM operation provides numerous benefits: better cylinder compression, lower frictional losses, improved propeller efficiency, cooler-running valves, lower EGTs and TITs, and a quieter cabin.

Cruise at the lowest RPM and highest MP that the book allows for the percentage of power that you desire. You usually have several possible RPM/MP combinations to choose from at lower altitudes in a normally-aspirated airplane, and at virtually all altitudes in a turbocharged airplane.

Lie #9:
Continuing to fly an engine beyond the manufacturer's recommended TBO is dangerous, illegal, and could void your insurance coverage.

Hogwash!

First of all, it's important to understand that TBO is an actuarial figure...the manufacturer's best guess about how long a typical engine will be able to operate before needing an overhaul. Some engines won't make it. Other engines will sail past TBO in great shape and provide many hundreds of additional hours of reliable operation before teardown is warranted.

Think of published TBO as being similar to published human life expectancy. We don't expect all humans to live to that age and then keel over. Some will die before their time, others will outlive their children. Certainly, we don't arbitrarily euthanize people when they reach the average expectancy age!

Published TBO has no legal significance for the majority of us who fly under FAR Part 91. For commercial operators under Part 135, TBO is theoretically "compulsory" because TCM and Lycoming publish their TBO figures in the form of a service bulletin, and Part 135 operators are required to comply with service bulletins. However, a Part 135 operator may apply to his local FSDO for a TBO extension, and such extension are routinely granted by the FAA. For example, one company that operates a huge fleet of Cessna 402s (published TBO is 1600 hours) has FAA approval to go to 2400 hours before overhaul.

Your aircraft insurance carrier could care less whether your engine is past TBO. Your policy simply requires that your aircraft and its pilot be legal under the FARs. As we've seen, published TBO has no legal impact on Part 91 operators. Part 135 operators need to ask the FAA's permission before flying past TBO, but such permission is commonplace.

We recommend that you overhaul your engine when it gets tired, not at some arbitrary number of hours.

Lie #10:
A factory reman is better than a field overhaul, because only the factory offers a true "zero-timed" engine.

While it's true that a factory rebuilt engine comes with a zero-time logbook while a field overhauled engine does not, it's not for the reason you may think.

When you have your engine overhauled by Mattituck, RAM, T.W. Smith, Victor, or whomever, that engine retains most of its original parts, as well as its serial number, data plate, and engine logbook or other maintenance records. The overhauled engine you get back is legally the same engine you sent in, all cleaned up with lots of new parts.

On the other hand, when TCM or Lycoming receives a runout core from a customer, that engine loses its identity. The data plate is removed and destroyed. So are the logbooks. The case halves are cleaned up, inspected, and added to a big pile of reusable case halves. The crankshaft is cleaned up, inspected, and added to a big stack of reusable cranks. The same is true of camshafts, rods, accessory gears, and so forth. Those reusable parts become "anonymous" because they're no longer associated with any particular engine serial number.

Now, when TCM or Lycoming builds up a factory rebuilt engine (colloquially but incorrectly referred to as a "factory reman"), it pulls some "anonymous" case halves from one pile, an "anonymous" crankshaft from another pile, and so forth. When the engine is completely assembled, it gets a new data plate, a new serial number, and a new logbook.

The logbook starts out at zero time-in-service. Why zero? Because there's no other reasonable figure to put in the logbook. The case halves are certainly not zero-time, but there's no record of how much time they've accrued. The crankshaft may not be new, but there's no record of how much time is on the crank, either. And so on.

In short, the "zero-time" logbook that comes with a factory rebuilt engine in no way implies that the engine is "newer" or "better" than a field overhaul. All it implies is that the reused components in the engine are of unknown heritage...nobody knows how long they were in service prior to the time then were cleaned up, inspected, and reused in your engine!

[PA1195]

Re: Carbon & Exhaust Valve

One technique I've used to monitor carbon buildup and oil presence (back to the original topic for a bit) is to periodically examine the spark plugs top and bottom on each cylinder, and also look at the head of the piston through the vacant holes. Shine a light through the lower, look in the upper. From new as rings seal and valve guides not leak too much the visible piston's head area that's wetted by oil (it's visible) will slowly drop towards the bottom. If it stays wet or climbs then more investigation (like with a borescope) is indicated. Same for any oil pooled on the lower cylinder when the crank is rotated to view the cylinder wall. Carbon buildup on valves can be seen as well through the spark plug holes, or better yet through the intake and exhaust ports when exposed as when checking a muffler for leaks.

I know a mechanic that likes to pull the valve covers periodically and examine that area for excessive carbon buildup and signs of heat caused by a leaking exhaust valve guide blowing hot gas into that chamber. Typically blowby out the oil breather will also increase when that happens (the gas has to go somewhere).

Edit. Consider all the millions of un-maintained lawnmowers that typically run/ran for years on 30W oil. Black, full of gunk, cooling fins clogged, never changed until they run low and seize. The owner then drains what's left just to see if there's any in there.

Gary

[Scott]

Re: Carbon & Exhaust Valve

Well our Continentals are certainly low-tech but at least a small step above your average Briggs & Stratton

Consider buying a USB camera. They're available for under $30, have built-in led light, and only 7mm diameter. Work very well for internal inspections of all kinds. Check out my Blog for lift strut inspection video done with a USB camera.

I've used Shell 15W50 in both private and commercial operations, for owned and customers' aircraft. I flew my Tcraft quite a bit on skis in cold temperatures with no preheat. The only winter kit was some duct tape over the lower nose cowl opening. This is where multi viscosity oils, especially synthetic blends provide a huge advantage. I can't remember the numbers but a surprisingly large percentage of engine wear occurs within the first couple of minutes of start-up. This is because, even though you have oil pressure, oil doesn't really flow and certainly doesn't splash. If you're in the south you're thinking no big deal around here, but if you're running a straight weight oil, then it's a bigger deal than you think. You still have a 100 degree give or take difference between a cold engine and one that's up to temperature. Multi viscosity oils also do better at higher temps. It is this broader operating range that provides the fundamental advantage, and made multiviscosity oils the lubricant of choice in almost all types of engines, aviation and none.

In my previous post I mentioned the lack of development that has occurred in the GA industry (should specify certified aircraft). IMO multi-viscosity oils is one of few developments to take full advantage of. I'm kind of surprised that there's still resistance to multi grades in 2015. I've run 15W50 in round engines, flat engines geared engines, supercharged, turbo, and even upside down engines (Gypsy Major) with good success, going well beyond TBO even in many cases. My 172 had just shy of 2500hrs and still strong, never removed a cylinder (the only reason I majored it is because of the lack of available places to land in this part of the world!). My A65 was in a box for over 23 years and when I did the top overhaul there was not a trace of corrosion anywhere. Anyway needless to say I think Mr. Bush's comments above about multi viscosity oils are surprising to me.

[PA1195]

Re: Carbon & Exhaust Valve

Respectfully Scott I enjoy your experience and thanks for sharing. Here's mine as a $$$$ paying owner. Let's not argue but learn.

Yes multi-vis has its value in some vehicles like Fairbanks at -50F. But for those of us that live and fly in cold climates and pre-heat below 20F, or at least as I've done so for 50 some years, viscosity at cold crank with adequate pre-heat becomes mute. However if you want high temp protection at high temps then use 50W oil. It's that simple. If the plane is at least regularly flown.

Multi-vis oil contains a suite of additives, including those that prevent corrosion...added I might ad to the product after Shell soon learned about the tendency to eat engines with their 15W-50 after it was introduced. Admittedly a lack of regular use or short term ops is the primary cause of corrosion, post-flight drain off in excess of single grade oil was another...but whatever the reason what follows is corrosion due to a lack of residual protection. Read ASL CamGuard's info: http://www.aslcamguard.com/products/aviation

I'll add if you'd guarantee TBO ops with multi-vis I'd follow that advice. If you condition that guarantee with minimum frequency of operation, then I suggest a single viscosity oil with an additive like CamGuard as a simple proven alternative.

One more final comment as I'd hoped to avoid a discussion involving tribology in this carbon/valve thread. True synthetics (like PAO's and Esters) are usually single grade lubricants. They normally require a mineral based oil added to carry any additive package intended to extend their viscosity range and offer improved features. That's what Shell did to produce their 15W-50 according to Ben Visser their former spokesperson. Exxon and Phillips have done similar linked to a sales price point versus perceived value to the consumer.

Like spouses, oil is a personal choice. And they can get expensive if not chosen properly for the expected conditions going forward. While it works when flow regularly, I'd not fly a multi-vis if it were free given my intermittent use.

Gary

[Scott]

Re: Carbon & Exhaust Valve

Absolutely, I continue to learn
For example, according to camgaurd's "independent" research 15w50 provided 4 times the corrosion protection compared with untreated W100.

Anyway it's all good, shows that flying often and keeping moisture out of your engine are the keys to success regardless of what oil is used.

[PA1195]

Re: Carbon & Exhaust Valve

Absolutely, I continue to learn
For example, according to camgaurd's "independent" research 15w50 provided 4 times the corrosion protection compared with untreated W100.

Anyway it's all good, shows that flying often and keeping moisture out of your engine are the keys to success regardless of what oil is used.

I saw that difference. Probably due to the anti-corrosion add in 15W-50 vs regular W100. I see now that Shell has newly formulated W80 and W100 called "Plus" with anti-corrosion/wear and combustion chamber cleaning elixirs: http://www.shell.com/global/products...s-w80plus.html

One thing older mechanics I've been fortunate to know have mentioned is the absence of internal varnish when using some newer multi-grade oils. It was their opinion then (1980-90's) that some varnish (but not excessive carbon) was actually beneficial in protecting certain engine parts like cams and lifters subject to corrosion in Lycomings.

Do you have an opinion or observation on that? I thought it sounded like a good thing but have little experience in looking at various aircraft engines and corrosion issues. CanGuard claims their product eliminates varnish which I suppose is ok providing their stuff offers similar protection.

Gary

[dkenney1]

Re: Carbon & Exhaust Valve

I saw that difference. Probably due to the anti-corrosion add in 15W-50 vs regular W100. I see now that Shell has newly formulated W80 and W100 called "Plus" with anti-corrosion/wear and combustion chamber cleaning elixirs: http://www.shell.com/global/products...s-w80plus.html

One thing older mechanics I've been fortunate to know have mentioned is the absence of internal varnish when using some newer multi-grade oils. It was their opinion then (1980-90's) that some varnish (but not excessive carbon) was actually beneficial in protecting certain engine parts like cams and lifters subject to corrosion in Lycomings.

Do you have an opinion or observation on that? I thought it sounded like a good thing but have little experience in looking at various aircraft engines and corrosion issues. CanGuard claims their product eliminates varnish which I suppose is ok providing their stuff offers similar protection.

Gary

Wow I never imagined my question would spawn such spirited conversation, but I love it and am learning a lot, but admit get confused at times too. I enjoyed reading the 10 Lies. Something tells me Letterman will not be doing them, but maybe a marital counseling book will. I guess the big takeaway here is, make sure there's oil in it of some sort because some will like it some will hate it, and the other is to fly regularly. My AI tells me all the time "the worst thing you can do to an engine is not fly it, 2nd baby it too much, 3rd take short hops and not get it hot". To keep mine flying this winter I'm going to have to purchase a preheater. That's a whole new question, but there are many types I'm finding and prices are crazy $400+, yikes!!! But, that's a lot cheaper than a cylinder. When gliding to a forced landing in a field without skis, I doubt anyone thinks, "I'm glad I saved that $400".

Darrin

[PA1195]

Re: Carbon & Exhaust Valve

Wow I never imagined my question would spawn such spirited conversation, but I love it and am learning a lot, but admit get confused at times too. I enjoyed reading the 10 Lies. Something tells me Letterman will not be doing them, but maybe a marital counseling book will. I guess the big takeaway here is, make sure there's oil in it of some sort because some will like it some will hate it, and the other is to fly regularly. My AI tells me all the time "the worst thing you can do to an engine is not fly it, 2nd baby it too much, 3rd take short hops and not get it hot". To keep mine flying this winter I'm going to have to purchase a preheater. That's a whole new question, but there are many types I'm finding and prices are crazy $400+, yikes!!! But, that's a lot cheaper than a cylinder. When gliding to a forced landing in a field without skis, I doubt anyone thinks, "I'm glad I saved that $400".

Darrin

Alaska = heaters in winter. If you have access to electricity (120V plug-in/small generator/DC to AC inverter off your vehicle battery) then there are many options. Some attach to the engine cylinders and oil sump, others can be placed in the engine compartment (search "car 120v heater"). External heaters can range from propane/12V fan models (https://www.flameengineering.com/pro...category_id=12) to kerosene burners (http://www.reddyheaters.net) to catalytic (http://www.walmart.com/ip/Coleman-Bl...eater/13228605).

Just some examples and no particular recommendation implied. I've used them all at one time or another both with electricity and without, and in town and at remote camps. To go with the heat source you'd need a propeller and engine cover to help contain the heat. The prop if metal is a great heat radiator and absorber for the crankshaft and engine internals.

Maybe this is best discussed in another thread.

Gary

[Scott]

Re: Carbon & Exhaust Valve

I saw that difference. Probably due to the anti-corrosion add in 15W-50 vs regular W100. I see now that Shell has newly formulated W80 and W100 called "Plus" with anti-corrosion/wear and combustion chamber cleaning elixirs: http://www.shell.com/global/products...s-w80plus.html

One thing older mechanics I've been fortunate to know have mentioned is the absence of internal varnish when using some newer multi-grade oils. It was their opinion then (1980-90's) that some varnish (but not excessive carbon) was actually beneficial in protecting certain engine parts like cams and lifters subject to corrosion in Lycomings.

Do you have an opinion or observation on that? I thought it sounded like a good thing but have little experience in looking at various aircraft engines and corrosion issues. CanGuard claims their product eliminates varnish which I suppose is ok providing their stuff offers similar protection.

Gary

I'm not really sure what "varnish" is. In the context of engine internals its one of those subjective terms that perhaps means different things to different people. Many engine components take up an amber to light brown hue over time. This might be described as varnish and is harmless. Possibly has some protective qualities similar to "blueing" (steel quenched in oil). Then there's the thicker deposits that tend to form around hot parts, also harmless for the most part. The "varnish" that I think we're concerned about is formed by a combination of heat, byproducts of combustion, and movement. I think it can be described as polished baked-on carbon. This is the stuff that causes our exhaust valves to stick and cause oil control rings to stop controlling oil There's a chicken and egg question however ie is the varnish the cause of the problem or the result of some underlying problem. I think in most cases its the latter.

My experience is limited to Shell 15W50 and yes there was a noticeable difference in how clean the internals appeared. Cams, lifters, pushrods, tappets... you won't find varnish on the contact/pressure surfaces of these parts. Look at the cam lobs of a healthy engine and they're polished to a mirror finish from the point where the valve spring begins to be compressed until the valve is closed. If there is any amber/brown hue here the valve is stuck or spring defective. Anyway no varnish= no possibility of varnish protection of cam/lifter regardless of the type of oil. Lycoming went through a phase of cam/lifter problems which I think had more to do with the hardening process (or lack thereof) than lubrication.

[Scott]

Re: Carbon & Exhaust Valve

Wow I never imagined my question would spawn such spirited conversation, but I love it and am learning a lot, but admit get confused at times too. I enjoyed reading the 10 Lies. Something tells me Letterman will not be doing them, but maybe a marital counseling book will. I guess the big takeaway here is, make sure there's oil in it of some sort because some will like it some will hate it, and the other is to fly regularly. My AI tells me all the time "the worst thing you can do to an engine is not fly it, 2nd baby it too much, 3rd take short hops and not get it hot". To keep mine flying this winter I'm going to have to purchase a preheater. That's a whole new question, but there are many types I'm finding and prices are crazy $400+, yikes!!! But, that's a lot cheaper than a cylinder. When gliding to a forced landing in a field without skis, I doubt anyone thinks, "I'm glad I saved that $400".

Darrin

You could try my "poor man's preheater." Before I Insulated my hangar I used two heat guns mounted on a step ladder at the right height and distance apart to blow warm air into the front cowling. You'll be amazed at how well this works. The aircraft needs to be out of the wind though and need to be mindful of your paint. But for less than $50....

[3Dreaming]

Re: Carbon & Exhaust Valve

Around here we have several that use a home made heater made from a cheat space heater, some heater ducting from the hardware store, and some flexible dryer duct. Works great and only about $50 in parts. It works best to have it of the ground and out of any possible fuel vapors.

[M Towsley]

Re: Carbon & Exhaust Valve

I think what Tom, above, is talking about is what is commonly called a milk house heater. They can be found at Farm & Home-type stores. We have several people around here using them. A duct adapter can be made, or bought, attached to the front of the heater and metal expandable/bendable tubing is used. You squish the end enough to stick in the bottom of the cowl and you are good to go.