Just finished the last one, what a major pain in the buttocks job.
I've been at this on and off for the past few weeks with being busy at work so been tackling one task at a time when I had a few hours run at it.
I am glad I had prepared by picking up the jig. It contains locators, cobalt bits, hardened steel drill guides etc for on a trip to the states. I saw it as an insurance policy and might save a lot of money in the long run. The kit has a machined locator that is shouldered to sit perfectly over the remaining knub of the broken bolt. The main locating frame is then clamped in place by two other machined locators.
You drill a small indentation then swap out that locator for a hardened steel drill guide and drill dead center through the bolt. Remove it and jump to the larger bit which is sized to leave the male parts of the bolt threads in the female thread part on the block. Sometimes most of it will come out on others you just needs to dress it with the tap and clean it. Three targets and three times it worked perfect. No stripped threads and no need for helicoils.
Its still not an easy job ,very time consuming as its a slow and easy type approach that works best. Each bolt probably took 3 hours from start to finish. Having said that though you do end up with the original threads in perfect nick so its very satisfying and should it have to come apart in future I know what I am dealing with.
I've cleaned off the gasket surface with steel wool, dry 240 and wet 240. It feels smooth but I'm not sure if I should keep cleaning or if its good enough to start reassembly which I'll do next week. I'm also putting new sleeves and clamps on the u bends at the back box so will fire her up to see what a straight pipe flat 6 with just the manifolds and cats fitted sounds like. I'm guessing loud.
Advice on the surface cleaning welcome. Before and after pics:
The threads on the last one to be drilled out and was also the original broken one. That pic makes me smile!
I'll update more next week when I get it back together assuming I have the time. I have also recorded various bits so may stitch it together on youtube at some stage in the hope that it might benefit someone else or convince them to take it to an indy.