Compression and Detonation Testing, #1

Builders,

I am going to cover this test project in a short series of articles. Below are some photos of the test hardware we will be using.

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As the title implies, we are going to run two separate tests, and share the data. I am going to put the results on You Tube also, because I want builders to see the results in action.

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The Compression test will be done first, it is fairly straight forward. I am building the engine, giving it a break in run, and then checking the differential compression, and running a base line full power run and noting the full RPM the engine makes.

I am equipping one head on the engine with small threaded ports next to spark plugs. For the base line run, these will be sealed. For the second test, I am going to open them up so the engine differential compression tests near zero 0/80) on those cylinders, and run the engine again and check the full RPM in comparison to the base line.

There is a widely held, but mistaken belief, even among aircraft owners and mechanics, that a cylinder with a differential compression of 40/80 makes half power, and one with 0/80 makes none. Neither of these are remotely true. The differential compression just measures flow against a known orifice, and does not correlate to any percentage of power out put. If the myth were true, the test engine with the three ports open would make less than 50% power output, but as we will see, it will do far better than that.  From professional dyno testing done by Dan Weseman and myself last year, we will be able to put HP numbers on the test stand RPM outputs, and the comparison will be enlightening to many people.

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The second part of the test is to show how rapidly, and how much power is lost when an engine is detonating.  Again, I will establish a normal running base line for the engine, and run it at full power for one minute at that setting.  This will be immediately followed by intentionally over advancing the timing to make the engine detonate. Several things I want people to see:

The engine will actually appear to run better at idle.

It will not detonate at modest power output.

When the throttle is advanced to full power, it will run normally for a few seconds, and when it reaches ‘kindling temperature’ it will suddenly begin to loose power.  This power loss will be far in excess of the engine running with 3 cylinders with zero differential compression.

If the throttle is not retarded, the power will continue to drop, to well below the level required for flight.

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We are working to get the engine instrumented with recording CHT’s and EGT’s for the detonation tests.  These will show a very sudden spike in CHT’s and a decrease in EGT’s, as all the BTU’s in the engine are destructively going into the heads. I will be working to capture this on video, so everyone can study the effect, know it when they feel it in their plane, and abort their test or take off. Again, a person with a correctly built engine and set timing will not experience detonation, but over the years, I have had a shockingly high percentage of people refuse to set their timing with a light, and I have people who never took advantage of my 39 free colleges to learn it directly from me.

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The last part of the tests will be a disassembly of the engine, after it has been detonated to the point where it would no longer make enough power to sustain flight, to show the internal damage done.  Because we teach people to use forged pistons in Corvair motors, and because the head studs in the engine are 9″ long instead of 1″ like a Lycoming or Continental, the visual results will be different.  I will carefully document the changes on the engine as a reference for people inspecting engines.

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The engine in the tests will not have a fifth bearing, nor will it have new seats and guides, and afterword, I will salvage some items like the prop hub and starter, but these test will still be expensive, costing several thousand dollars and perhaps two weeks of labor.  I am conducting them so builders will have a chance to learn something. It this happens the time and the money will have been well worth it.

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Test engine, 2,700cc’s. This bottom end came out of one of the two core motors we found. The plastic orange plug set is a kit sold by SPA/Panther specifically for Corvair storage and painting. Note, old style bell housing cover in place of 5th bearing.  This engine isn’t going flying, and the tests are all taking place in the combustion chambers.

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Heads getting reworked at SPA/Panther in advance of the tests. Travis Young (aka “Retro Black”) took care of the machining operations.  Their machine shop is set up for both engine and airframe parts production. The heads are getting perfect head gasket machined surfaces, and welded on intakes, but the valve job and the guides are just street car level work. Again, the motor will run for less than one hour, it doesn’t need new guides.

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Engine getting decked in the mill. These surfaces are now perfectly true and flat. After severe detonation, warping in the heads can often be measured directly with a straight edge. The head gasket areas are often impressed into the heads, and the lower row of studs can become misaligned. Detonation puts a tremendous amount of heat into the heads, enough that they will plastically deform.  Most people think of detonation putting holes in pistons, but it only does that on cast pistons. On forged Corvair pistons, the damage is more subtle, the oil control rings become stuck in the grooves. I intentionally specified forged pistons because the engine will actually tolerate a lot of abuse with them. They are a margin  of safety on small mistakes, but they will not provide immunity for fools.

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Head bolted to a fixture plate in the Mill. The unit is a very nice Chevalier with DRO. It is in good shape, having lived in a tool room most of it’s service life. Next time you See Dan at a College or an Airshow, you can get him to share the story of how he bought this piece of equipment for $6.

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“It ran great when we parked it”

Builders,

Vern and I picked up two core motors on Saturday. Vern knew the owner very well, and he had them both for more than 25 years, stored inside, in a dry place, but not sealed. Vern even knew the Corvair collector, another friend who sold these engines to the man we brought them from. Below are some pictures to illustrate why you should carefully store your engine following the advice I wrote in this story: Storing a completed engine.

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Upon inspection, each engine had 2 cylinders which were clogged with corrosion. Why? because on a Corvair, one exhaust valve on each side of the engine is always open. If the exhaust isn’t sealed, or the engine isn’t in a bag, over a long period of time, those cylinders will rot. This is why I have always said to bring a 3/4″ wrench and turn the engine 360 degrees to make sure it doesn’t look like this inside. These motors didn’t rotate at all, although they were probably perfectly fine when pulled from a car thirty years ago.

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Above, “Weird scenes inside the gold mine” . Think about how many times someone has told you the BS that lead in fuel is “good for valves” as if  it was the 11th commandment.  I have said this a zillion times: “The byproducts of combustion of leaded gas are highly corrosive in the presence of any moisture.” Leave it for a week , or a month, fine, but not longer. This is why we use unleaded fuel to break in motors at colleges, because they will be stored before use.This engine probably did run great the day it was pulled from a car. But with the exhaust left open, it formed this corrosion in two cylinders. The engine was filled with lead, so I am guessing the last time this engine ran in a car was in the mid 1970s. Historical note: I have been working on engines for decades, but I have never seen a Valley Forge brand spark plug. Maybe the specialized in the cold end of the heat range.

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Judging a book by it’s cover story: When we got the engines back to my hangar, I knew they were going to need a fair amount to work, so I broke out the pressure washer and the 375,000 BTU steam generator. Combined with a generous dose of purple cleaner, the engines looked very good on the outside in a few minutes. When engine shopping don’t care if the engine is clean, only if it rotates. Counterintuitive Grease Monkey Experience: an engine that is covered in goo on the outside constantly leaked oil, and thus had a continuous oil change going on. This motor invariably looks better inside than one which drove the last 3 or 4 years without an oil change. Besides, an oil leak core motor began the “self cocooning” anti-exterior corrosion process before hibernating a few decades waiting for you to need a flight engine core.

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Above, another hint at how long this motor was stored: When was the last time Shell sold spark plugs?  Look at the size of chemistry project going on in Cylinder #2. Part of what drives this process is the fact Corvairs have aluminum heads and iron barrels, diving a dissimilar metals factor an all iron car engine would not have.

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Preservative and cage free lunch in rural Florida. 

Builders,

When you speak in terms like “Cage free”, “Non Genetically modified”  and “all natural” people from more densely populated places just assume you are speaking of a trip to the Whole Food Store or one of those places where ‘enlightened and aware’ people shop.

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Well, here in Florida, we have just such a place in our little rural town, except it is also our local NAPA auto parts store. On Fridays in good weather, lunch is served to the staff and regulars. Today it was particularly fresh pork, which was smoked out back since 7am. Not only was it delicious, but it also met all the credentials touted by the enlightened such as no preservatives, cage free, etc.  It is a nice part of living in a place where people are well aware that food does not originate at Supermarkets, and there is a sure fire way of assuring that your food is all natural.

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I don’t think you can taste antibiotics in supermarket ham, but by comparison it insanely salty, and the ‘glazed’ stuff is only processed sugar coated. I am not a ‘foodie’ but when you are exposed to real natural food, it is a real moment of awareness on how far from normal consumer taste has been dragged.

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Above: I took the photo of the smoked pork on my plate. Just above it is The NAPA store owner’s phone, with a picture of what my lunch was doing a few days before.  Feral hogs are an invasive species in Florida, and they not only do extensive crop damage, they also harm native animals. The fact feral hogs are tasty combined with the high percentage of firearm ownership in Florida works to restore the natural balance in the environment and provide lunch at NAPA. Other than the last 1 second, this animal had a far more humane life than any animal existing in a ‘food’ factory. Lest anyone claim an AR has no sporting use, this meal was provided by an AR-15 chambered in 6.8 SPC.

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Needed: Core motor close to running.

UPDATE #2: Tomorrow at 6am, Vern and I are driving over to north central Florida to pick up two running Corvair engines for $500. Although we had many very thoughtful offers that I found moving, the best option to stay on the time line was to get an engine here locally. I missed Vern yesterday, but when I mentioned the project to him today, it took him exactly 4 phone calls to find just the right motors at the right price, within 90 miles. More news at the end of the day tomorrow. 

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UPDATE: Several people called to generously offer the use of their flight motors. Let me clarify what I am doing. I am going to run a destructive test on the engine. The term “core” doesn’t mean the middle part of a flight motor, I mean core as in the rebuild able unit as removed from a car.

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I am going to first put a prop hub and a starter on it, and run it as a base line. Then I am going to set the timing with 8 degrees too much advance on car gas, and I am going to show that it will run for 15 seconds before going into detonation, and when it does the power will decline rapidly. Before it blows, I will stop this. Next, I am going to differential compression test it. Then I am going to drill a 1/16″ hole in 3 cylinders just below the head gasket, and run a differential compression test to show each of these cylinders reduced to 0/80 compression. With the timing set correctly, I am then going to prove that a motor with zero differential compression on half it cylinders will still have plenty of power to fly a plane. when this is done, I am going to set the timing with too much advance, and run the engine that way until it blows. All this will be filmed and documented. This is why I need an old engine out of a car, not a newly rebuilt motor. If someone was planning on using their core for a rebuild, I will replace any part I break or render unusable from my own core parts collection.  

Builders:

I am going to run a very specific test on the run stand, and I am looking for a regular, stock 95 or 110HP car core engine to do this with. I need the results in a week or so, thus I am asking for help finding a test motor.

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All I need is an assembled case, pistons and cylinders, and heads for the test. It doesn’t need to have carbs alternator, nothing else. It will just save me a bunch of time over assembling a greasy core from worn parts to run a 20 minute test on the stand.

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I will gladly buy this motor, or if it is a builder core I will come and pick it up, or you can come to my hangar for a day of interesting testing, and then we will tear it down and get it started being processed into any flight engine you would like. Several different options here, the only critical element is I need to move forward this coming week.

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If you can help, use the comments section, send me an email to WilliamTCA@aol.com, text 386 451 3676, or call. Glad to listen to any options.

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Above, Grace takes apart a core engine at Corvair College #3 at Spruce Creek Florida, 2002.  With her is Gus Warren and Mark Christmann. The engine I need today could be just slightly more assembled than this.

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New 2,775 cc Corvair for a Zenith 601XLB

Builders,

Below are picture of a newly built 2,775 cc Corvair running in my front yard today. It came to life at 3:45 PM after 2 seconds of cranking, and put down a perfect cam break in run. The engine is completely built out of FlyCorvair/SPA parts, and represents a great example of Corvair power at a moderate cost. The engine was ordered by a Zenith owner who bought a complete and flying 601XLB with a older, tight budget built, 2,700 engine. The owner liked the combination, but realized that his existing power plant was not state of the art a decade ago, far less today. Ordering a fresh engine from us was the fastest way to correct this.

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Although we make engine in several different displacements and outputs, we make them at only one quality level. The 2,775 is the smallest of our production engines, but it has long proven to be plenty of power for a Zenith 601/650. The first 2,775 Corvair was the engine I built for our own Zenith 601XL in 2004. Thirteen years later, it has a great number of refinements, but it is still a smooth running American, designed, built and Converted aircraft engine. If you would like to find out more about buying a Corvair for your plane, please call Rachel at the engine hot line 904 626 7777, extension #1.

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Above, the head on view. Someone smarter than myself about digital cameras will have to explain how the image is reconstructed that places the prop blades at such angles. Please do not try to explain it to me, I am a simple aircraft mechanic who barely understood how chemical film worked.

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Above, this is what a valve cover finished in “Retro Black” looks like.

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Engine in operation, viewed from rear quarter. This engine features all the same quality parts inside as larger Corvairs we build, but just in a smaller bore size.

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Above, engine a few minutes into it’s 30 minute cam break in run. This is followed by an inspection and a longer run to make sure the cylinders pistons and rings are set.

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A special note of thanks goes out to the owner of this engine. He ordered is a while back, before my father passed, and he was pretty civil about waiting for me to come back after the services and CC#39 to finish. After tomorrow’s runs, the engine will be crated and on the way to him shortly.

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This was the last engine on the order sheet to be assembled. The “Engine in a box” kit engines are selling very well, but with the Weseman’s covering the distribution of my parts, I am now actually caught up on orders for fully assembled engines. I have not been able to type that sentence in several years.

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The combination that made fixing this possible is two fold: Today the Weseman’s work is complementary to mine, they provide every Corvair part I don’t,  particularly the heads. For many years every engine I build used Falcon heads, and they were good, but produced in a trickle that left people who ordered an engine from me waiting. Today the Weseman’s make heads which are every bit as good or better, and they do it on an industrial scale. They have made more heads in the last 2 years than Falcon did in ten. Second, having the Wesemans distribute my parts has allowed me to focus on building them and teaching at the colleges, and left me the time to spend with family. So while the picture above may look like just another running Corvair engine, it is a milestone I am most grateful to have reached with the help of friends.

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As seen at CC #39 Barnwell…

Builders,

A few photos to share the flavor of Barnwell. Again, hats off to PF and crew for their eighth College.  We are already making plans to return for CC #41 in November. Don’t miss it.

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Use the comments section to share your questions , thoughts and thanks.

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PF’s Pietenpol. At the College he flew his 300th different passenger, Chris Pryce.

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Bob Lester shows the Harley kick starter that he rigged up to light off his engine.

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Dale Williams 3000cc Cleanex on its 4th visit to Barnwell

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Don Harpers Pietenpol.  Don had a stunning upset political victory over an entrenched incumbent last year.  We need someone to print shirts that have a Pietenpol picture and say “Harper4POTUS2020”

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The Barnwell terminal is very plush inside.

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Bob Dewenter contacted EAA headquarters about proper recognition for the crew for all the work they have done in support of “learn build and fly” This came from the Chairmans office.

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Attention Piet builders; PF has some very nice parts for sale, including this center section with fuel tank, a set of Riblet ribs and a set of tail feathers

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Shelley Tumino wins the award for most elaborate campsite with her hand made tear drop trailer brought in from TX. CC #40 is at her place in October.

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Tail on Don Harpers Piet shows he is a native of the Palmetto state.

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Tim Hansens custom shirt on home building.


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Above three Corvair Piets in typical Barnwell weather. Don’t miss the next one.

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“Captain Morgan” Contest at #39

Builders.

We have a long College tradition of having your photo taken with your running engine. Often, after two or thee intense days of building, learning and fun, builders posture reflected exhaustion rather than the internal elation they were feeling. To make a better picture, I told each of them “Picture yourself standing the same way as the pirate in the Captain Morgan rum ads.”  It worked very well, and ever since we have had much more jaunty pictures of first engine runs. Use the comments section to vote for your favorite “Captain Morgan”.

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Lou Cassella, Pietenpol engine.

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Joe Pringle, Zenith engine.

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Bill “Snow suit” Beauvais, Pietenpol engine.

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Terry Lambert, Zenith engine

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Bill Mills, Zenith engine

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Charlie Johnson, Dragonfly engine.

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