DILEMMA time....

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:

These cam bores look much better. The marks in them can be buffed out. The light brown you see on the casting seems to be an oily dirt substance which wipes off with a finger.

It definately needs a bath, but internally much better than the 140hp case.

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:

East-outs are hardened bits with an aggressive reverse twist end which are inserted into a centre drilled bolt. As you turn the bolt out it grips tighter.

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.