Took an hour today to start cleaning up the push rod tubes that I removed from each of the cores:
First step was removing the old dry and cracked o-rings. GM used simple rubber ones which in the conversion process are replaced with Viton rings. Viton doesn't dry out with heat and remain supple over the course of the engine's life. Some were already cracked and missing pieces:
I rummaged around in my tool box and found the perfect thing to use. Don't ask me if I know how sharp the point is:
Some came off complete, but most came off in brittle little pieces:
Next step will be to clean them up. First a bath in Simple Green to get rid of the grime and grease, followed by a polish. The tubes are made of light steel with a zinc coating. GM left them bare, but standard practice for conversions is to paint and bake them white with high heat enamel to enhance cooling (or at least reduce heat transfer to the tubes from the cylinders). I've read online it's best remove the zinc coating and this can be done using an aggressive Scotchbrite pad or bench grinder wheel.
I haven't posted anything to my blog for a couple of weeks because I've been busy doing the other things in life that keep our family hopping at this time of year. Vacation, two birthdays, two anniversaries, the end of the school year, fireworks shows for Canada Day (another hobby of mine) and some camping. All this happens in the span of 14 days. But it's over again for another year.
Of course my mind hasn't strayed too far from my project and I'm starting to narrow down my decision on what airframe I want to build. In my post from last year "So Many Choices" I describe my thought process in this regard.
Just before I started vacation, I managed to meet up with Ron, a local home builder who has vast experience with building aircraft from scratch, from kits and rebuilding damaged airframes for others. He is currently working on a Piper Pacer, but he has offered me a spot on his build team and more importantly, the opportunity to assist him and another guy in building a Zenair 701. You can't ask for better chance to learn from someone that has "been-there-done-that". Ron is also keen to see a Corvair installation process, perhaps for future build of his own.
So, after much debate and thinking out the pros and cons I've decided 99.9% that I'm going to begin the process of building a Zenair 750 STOL (Short Take Off Landing). This aircraft has the best of everything I'm looking for:
One thing I really like about the home building movement is the willingness of others to share what they have learned and help others get started. It's a tight knit group of individuals and it's great having that support network when working through a build.
During my vacation, I got a call from another Corvair builder named John who is putting a Corvair in his Zenair 650. His engine was built for him by William Wynne and he is close to flying his 650 for the first time. He reached out to me after seeing I was also in Ontario in hopes of having another Corviar builder to bounce ideas off of (again, that built in support network is great). He also offered to put me in touch with yet another Corvair builder who is doing the same 750 airframe that I'm interested in.
I told John I was planning on heading to the Zenair open house being held in conjunction with the Midland RAA (Recreational Aircraft Association) fly-in being held this past weekend. We agreed to meet up in person and that's exactly what happened yesterday.
I arrived at the Midland Huronia Airport sharply at 9am Saturday morning. I was hoping to meet the Zenair staff before the crowds got too busy. I had the opportunity to speak directly with brothers Michael and Nicholas Heintz, sons of Zenair aircraft designer Chris Heintz. I explained my goals and mission and they answered any question I had. When I mentioned I was planning on putting a Corvair engine into the airplane, they were very positive about the combination which is extremely encouraging.
Michael advised me that a builder from Newfoundland by the name of Jeff Moores was coming that day to look at purcashing a Zenair 750 and was a Corvair builder as well. I've had conversations with Jeff via the Corvaircraft forums, as he has already built a Corvair for his Merlin ultralight, so it was great to meet him and his wife Dale in person. Shortly after, John walked over and introduced himself.
Jeff, John and I talked at length about each of our plans and how we are at substantially different phases of the build. having built both a 2.7 litre and 3.0 litre Corvair engin, Jeff offered some great insight to the differences and advantages of each. Considering none of us had ever met before in person, it amazed me how quickly we became friends - guess that's all part of being a builder.
We took a tour of the production facility where Michael explained the evolution of Zenair kits and how advanced the CNC production has become, even just in the last few years. The 750 kits are considered state of the art and are "match drilled" meaning all the holes in the pre-formed aluminum parts are already drilled for the builder, saving substantial time in assembly. It was clear from the tour that the kit quality is top notch, and I came away from the tour feeling very confident that this is a great project for an amateur builder like me.
As the morning progressed, each of us were offered a flight in the factory 750 demonstrator with Nicholas Heintz. This one is actually the 750 Cruzer model, which has a somewhat cleaner airframe (no slats, different wing, etc) resulting in a somewhat faster cruise speed than the STOL model, but the cabin dimensions and "feel" are the same. The demonstrator is equipped with a Jabiru engine (which is has approximately the same horsepower as what a Corvair would:
Now, I'm not sure what my goofy smile was from; the fact I was actually going flying or how pleased I was to experience the visibility this cabin design provides (and I wasn't even in the air yet!) but I suspect it was a combination of both:
A short time later and we were airborne! I was so wrapped up in the flight experience and speaking with Nicholas about the handling characteristics of this Cruzer model vs the STOL version, I didn't get any puictures, but I am really impressed with this aircraft. Smooth, stable and comfortable. The visibility is incredible in all directions and the bubble doors give that extra feel of roominess. One thing I noticed when I had the controls and entered a turn was the really nice visibility through the clear panel cabin roof:
Jeff's wife Dale took some pictures and videos of my flight and when they get a chance will send them to me and I'll post them. Here are a couple of more I took:
So things are starting to pick up speed. I'm definitely in the arena and the game is about to really get started!
Well, my buddy Guy had some progress in getting the last three broken studs out on the 110hp block.
The first one came out fairly easy once centre drilled. Looks like the threads are still intact and should clean out nicely:
Number two, not so much. The centre of the stud hole doesn't always line up exactly with the threads, so he stopped working this one with the end mill until we can decide if we want to re-tap the hole afterwwards:
I tried using a large EasyOut bit but the last of this stud won't come out and I'm wary of damaging the remaining threads. I've filled up the hole with some home-brew penetrating oil and will let it sit for a couple of days to see if it will loosen up before trying again. I think I might be able to use a tap and just clean it out, but I'll wait for now on this one. This is likely the worst of the bunch.
Number 3 was the most interesting result. Using an EasyOut, Guy backed the stud out carefully, but unforuntately it brought most of the aluminum threads with it. It was stuck in there real good:
Now, the beauty thing of all this is that all 3 holes are salvageable. There is enough room left between each of the damaged holes and the cylinder bores to insert either a Heli-Coil or TimeSert thread repair. They each have their strengths and pricing differences and from what I've read they each work well (click the links to check them out). I kinda like the TimeSert method better, just seems more permanent. This will mean cutting new threads on the end of the replacement studs with a sharp die to match the repaired holes, but that is common practice and an acceptable repair for a conversion.
If I can't get the number 2 one out cleanly, it will be easily removed during the drill/tap/insert process of the thread repair.
I'm stoked this is going to work and I can use this block for my engine <grin>.
On another note, I've added a running total time log on the lower right of my blog page:
One of the things builders like to keep track of is the amount of time spent on parts of the project. I've broken things down into basic groups and will try an remember to update it regularly. I considered purchasing a commercially available program like KitLog, but I prefer this blog format. The 25 hours showing under Engine is just a rough guess and doesn't include non hands on time like time I've spent online and in person looking for a core. I might consider breaking the chart down further, but I'm happy with it for now.
Next step, research where to purchase TimeSerts.
Got a call from my buddy Guy (correct pronunciation is Gee, which is french Canadian) . Despite his best efforts to remove the broken studs he is struggling a bit. He tried welding a nut to them but they just snapped off further down and now they are sitting close to flush to the block. This leaves no option but to drill them out using a milling machine and end mill bit.
Fussy, temperamental work with a fairly high risk of wrecking the threads if not careful.
After finding limited success using the weld method, he tried centre drilling the stud in preparation to back them out with an EasyOut bit. This proved to be very difficult because the studs are a hard material to drill, but he did manage to centre drill one of the three. The other two he's going to use the milling machine as it should be easier.
The next concern will be how to clean out the remaining debris from the threads that gets left behind. The conversion manual is very specific that the lower end of the studs is a special thread called 3/8"-NC5. So at this point I believe I'll need a 3/8"-NC5 tap to clean out the threads. Even an experienced machinist like Guy had never heard of this particular thread (he checked with his suppliers too) and suggested it will be expensive to obtain due to it's rarity.
While my buddy worked on end milling the holes, I decided do do some research.online. Although I wasn't able to find a tap or die that matached this unique thread, I did come across an online archive of GM production drawings that show the machining dimensions of a Corvair engine! I really love the internet!
This is where it gets a bit more confusing. According to the dimensional drawing showing the machining instructions of the casting, the stud holes are supposed to be tapped to a dimension 3/8"-16 UNC:
But how can that be? The hole and stud should be the same thread as the stud..... hmmm.
I sent an e-mail to the internet Corvair conversion forum seeking some guidance.
Not long after sending the e-mail, I got a telephone call direct from William Wynne (the Conversion Manual author and recognized Corvair guru).
We had an almost hour long conversation about the conversion process, my overall plans and this particular issue regarding the studs among other things. He's very supportive of new builders like me that want to learn and his overall philosophy about home-building and being in the arena speaks to me.
He is an amazing person to speak with and very quickly confirmed that the GM drawings are correct, the stud holes are in fact 3/8-16 UNC. The reason the studs are slightly different is GM engineers wanted an interference (extremely tight) fit to ensure the studs would remain in place. Using a common 3/8-16 UNC tap would be appropriate to chase the debris from the holes.
Guy happens to have that tap (it's common) and I called him afterward to confirm what we know now to be correct. He's going to finish cleaning things up. In the meantime, I'll bring him the other half of the block and have him clean it up too. On the advice of William I'll also be contacting Dan Wesseman of FlywithSPA.com, William's recommended supplier for info on obtaining 12 new (to me) OEM matching long studs as the ones I have are too corroded to re-use.
To make things even better, Brenda tells me a fellow Corvair conversion builder called for me while I was at work and invited me to visit his shop near Barrie. He is building a Zenair 650 with a Corvair engine. It is almost complete at this point and offered to help answer any questions I might have along the way. I'll make contact with him tonight when I get home and maybe arrange a time to visit this weekend when I'm in the area for a family function.
Despite soaking those stubborn snapped studs in "homebrew", there is too little of them left sticking above the surface of the block to grab onto with a tool and back them out. For all I know, they'd come out now, but I got nothing that can grab onto them strong enough to turn.
I met up with my retired 911 buddy who is an accomplished machinist/welder/hobbyist to have a look at them.
He's taken my block back to his place for a couple of days to see if he can get them out. He figures he's got a couple of options to remove them and preserve the threads. I've told him to take his time and get to them when he can and he promised to be careful. Now that he sees my dilemma in person, he understands. He's the type of guy who likes a challenge and I have little doubt he'll be successful.
I've been pondering my options regarding the 140hp block I've been working on.
I'm getting concerned about the amount of corrosion on the camshaft bores. Originally I thought it was just transfer rust from the came, but it looks like it might be more.
In Corvair motors (and other major air-cooled engines) the camshaft rides in bearing-less surfaces bored into the block. These are polished surfaces and the cam rides in a coating of preassured oil provided by lubrication passages. In a running motor, it is critical that these bores are clean, smooth and round as possible. I haven't tried everything method I have in mind to clean these yet, but however it gets clean, I can't just grind away the corrosion and it looks like it's more than just stains. The risks are removing too much aluminium and making to bore over size - there are no options if that happens. Here are a couple of pictures of some of the spots I'm worried about:
The 140hp block needs a lot of work to remove the corrosion (these aren't the only spots, the cylinder bores are also poor), and it may just be a wasted effort if the cam bores won't clean up properly. So, in the meantime I've decided to have another look at the 110hp block and see if I've exhausted every effort to remove the 3 snapped studs that halted me last time.
I hadn't taken the case halves apart on the 110hp block, so that was the first step. Internally, it is much more promising. The cam bores are beautiful and will require a bit of polishing. Even better, all the mating surfaces look fantastic. I haven't measured any of the bores for specs, but they look near new and should check out okay:
Refreshed with information, I took the case half with the broken studs outside. Here are two seperate pictures of the 3 studs I've got to somehow figure out how to remove. As you can see, I haven't got a ton to grab onto:
Now, I'm not the first person to have this happen to their block. Some of the suggested methods are to weld a nut to the top of them and use a wrench or socket on the nut to back them out. Another is to drill the broken stud out carefully in the centre and use an "easy out" bolt remover like this:
I think I'll try the second method first and use the welded nut as a alternative if that doesn't work.
In preparation, I've soaked the three broken studs in some "home-brew" penetrating oil (see my previous posts) and I'll let them sit for a couple of days:
Maybe, with a little luck, I can use vice-grips and they will come out without having to drill or weld.
I've got a retired buddy who is amazing with machining, if that doesn't work I'll contact him for suggestions on the next course of action.
Today was supposed to be about cleaning.... but I also managed to get past a recent roadblock that has been keeping me awake at night!
Today's first step was to remove the oil gallery plug from each side of the engine block. I've read that on 50% of engine cores these never come out, but both of mine came out easy with a 1/4 inch extension on a ratchet:
Next, I filled a tub with hot water and Simple Green (just like the head studs a few days ago). This is the case half that didn't have any studs remaining. I wasn't sure I'd be able to fit the second case half in, but at least I can get started on this one:
While this was soaking, I decided to have another go at those two stubborn head studs. So far no amount of PB Blaster or gentle persuasion has convinced them to move even the slightest. A couple of days ago (see my last blog entry) I added a little of "home brew" mix to the studs.
I had the time today to give another try at removing them. I didn't expect 48 hours would be enough time for it to soak in the ATF and acetone "home brew" mix but WOW! They came out very easy with very little wrenching! The "home brew" worked AMAZING!
Now I've got the best chance to install all the head studs even and properly and stop worrying about two that were only partially into the block. Very cool!
By this point, I was ready to get started on cleaning the case halves. Just to prove that I'm actually doing something, Brenda took some photos of me scrubbing away some grime:
Both halves somewhat complete, a quick pressure wash to rinse off the dirty water and drying in the sun:
They look great, but as they dry I notice some spots that will require some more cleaning attention. Lots of spots that are hard to get at with a scrub sponge, I'll have another go with a toothbrush and maybe the Dremel tool and a 3M wheel. I also see a bunch of casting flash from the factory that needs to be removed to improve oil flow. It's surprising how little GM did in this regard.
I have some rusty spots that will also require some attention. I'll do some research on the best way to address this.
Good progress today, especially the last two head studs. Moving on!
Spent a couple of hours this morning doing some detail cleaning on the head studs and case bolts. I started by placing them all into a RubberMaid bin:
Next, I covered them with a couple of inches of hot water and approximately 1 cup of Simple Green cleaner. This resulted in a cleaning solution equal to about a 10:1 ratio, the recommended strength listed on the jug:
I decided to let the whole batch soak a bit. While I waited, I brought the engine case half that has been giving me trouble with the studs outside. I wanted to try the home-brew penetrating oil I've read about online that others have tried that worked.
The home-brew penetrating oil is made by creating a 50:50 mix of automatic transmission fluid (ATF) and acetone. I bought some acetone the other day and had some ATF lying around:
I didn't want to make a huge batch of this stuff as I only have two studs to work on, so I took some old medical syringes I had and measured out just enough equal amounts of each and mixed them in a old plastic coffee can:
Once mixed, I used one of the syringes to add a generous amount of "the brew" to the base of the stud where it enters the block:
Over the course of the next two hours, I used dish sponges/scrub pads and a bottle brush for the case nuts. Once the grease was off, I was pleased to see the studs were in good shape, with little to any hard tool marks or signs of twisting. The threads also seem in amazing shape. The rust you can see is just on the surface without any bad spots. The studs get painted once installed in the block, so I'll clean them up some more with a wire wheel before I prime them for paint.
I clearly have more serviceable short studs and may have to order new long ones as the thread ends are badly corroded off, leaving limited threads available:
I put everything back into inventory for now. I'll keep adding "the brew" to the stubborn head studs and then give turning them out a try - at minimum, if they don'e turn, I can be fairly confident they will stay in place.
Next up.... the case halves take their turn in the bath.
It took some time, but I finally got back into the shop. The last few weeks have been real busy between work and family commitments, and I'm trying to keep moving forward.
This afternoon, I took another crack at removing the last two head studs. Unfortunately, they continue to be stuck half-way out of the block, and by stuck I mean they don't seem to want to go either way (all the way in or all the way out):
Next, I'm going to try something suggested by some on the interwebs - make a penetrating oil with equal parts acetone and automatic transmission fluid. So far PB Blaster hasn't worked, so why not? It apparently works very well in exactly this situation. So add acetone to the shopping list and check the shed for ATF, I'm certain I have some.
Rather than dwell on this, I thought I'd take the steps to separate the case halves. If you recall, I mounted the block sideways on the engine mount to prevent the crank and cam from falling out of the block as it separates. They came apart surprisingly easy with some light tapping on the non mating surfaces with a rubber mallet:
Getting a good look inside now! Crank is likely trash, way too much rust and pitting on the connecting rod throw bearings. The cam? Hard to say, but it looks bad too and maybe it can be salvaged but probably not. Disappointing, but I already have two good cores for exchange form the 110hp core engine, so no big deal. Found more rodent debris and I think this core has been sitting dry (without oil) for a long time:
Also conspicuously absent are any bearings. Looks like someone decided they didn't need to be replaced yet. That's okay, I'll need specifically sized new ones once the crank and cam are serviced.
Carefully removing the old crank and cam reveals some surface rust on the block bearing surfaces. I think this is more of a transfer of rust staining from the crank and cam and hopefully they should easily clean up:
I was a bit worried about the bottom edge of the block, but then realized that this mating surface is inside the engine (above the oil pan), so small leaks here although not ideal, are not an issue. A close look at it looks like this is the spot someone previous used to pry apart the halves:
They look better once I used the shop-vac to clean away the last of the mouse debris. The inside of this block seems pretty clean otherwise:
One final thing I did while putting away the crank was to try giving it the "ring test". It's something I learned from the FlyCorvair.com DVD. A simple test used to check a crank for cracks (especially hidden ones) is to hold the crank from one end and give it a light tap with a hammer. A good crank will "ring" for up to 20 seconds once tapped lightly.
I tried this.... my cranks rings, but not consistently. The first time it rang for a few seconds, the second time a bit longer but the third? "Clunk". Perhaps I'm not striking it consistently. Either way, this crank is likely junk with all the rust pitting. Just wanted to try it.
But at least it's all apart and I'll be able to start moving towards assembly of my new power-plant!
Next up.... taking out the oil gallery plugs (if they will come out!), start power-washing and hand cleaning everything....
Jumped at the chance to work outside this morning and pressure washed the 140hp block. The core is quite clean, but I wanted to remove some of the remaining grime and PB Blaster that I've been spraying before bringing it into the basement shop. It's not perfect (and won't be without some elbow grease, scrub brushes and Simple Green cleaner) but at least it doesn't smell greasy. Here is a couple of pictures, post "wash" and drying in the sun:
Obviously, I won't be able to get into all the internal nooks and corners until I split the case halves.
Once it was dry, I moved it into the shop and mounted it sideways on the engine stand:
I've decided to try and carefully remove all the studs as it looks like most will have to be pulled and re-installed with LocTite 620 anyhow. So, before splitting the case halves, I'm working on removing them. The easiest way to do this is to double-nut the studs at the top and back the studs out. This is much preferable to using ViceGrips or ChannelLocks and risking damaging the studs. It's a lengthy process for each, but worth the time:
Eight studs to remove and every single one came out cleanly on this side. A couple of them were tight, but a bit of 3-in-1 oil at the base helped. The threads in the block look great, should be good for re-installing the studs later:
Tomorrow, I'll rotate the block over and work on the opposite side studs. Only 11 to remove on the other side and they hopefully go as smoothly as these did. Then I'll review the dis-assembly DVD for direction on separating the case halves.
Husband, father and 911 dispatcher. Long time pilot with a licence that burns a hole in my pocket where my student loan money used to be. First time aircraft builder. Looking to fly my own airplane.