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:

Bad news:

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.

Good news:

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.

​Better news:

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.

Progress!

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.