Thread: A new car!
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Unread 08-06-2018, 02:50 PM   #170
GlenL
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Default Pulled the stud

Well... It can't all be roses.

When taking the studs out of the block I broke one. Shoulda applied heat again instead of cranking it harder. Hindisght is good like that.

The machine shop (TPIS in Chaska, MN) got the stub out and used Heli-Coil (M12x1.5mm) to fix the threads in the block. When I tried to put on the head it yielded below 35ft-lbs. The stud looked to have aluminum in the threads (no spring thing) so I figured they hadn't done a Heli-Coil and sourced the kit.

When I went to do the Heli-Coil I could see the old coils in the block. Took a while to fish them out. The block was drilled right as a 31/64 bit went in smoothly but not a 1/2". The trick is the instructions (deep down) say to use a slightly smaller bit for aluminum that's probably unobtainable. Using my hindsight (again) it'd have been best to go without drilling and be super patient to get the new, sharp tap to ream the hole as needed.

I cleaned up the hole and inserted new Heli-Coils. They had 2 18mm coils and I used 3 although about the last 8mm just hung out of the threaded section. (The threads don't go all the way to the top.) This time it torqued to 55ft-lbs but failed going to 80ft-lbs. The cheap boroscope I've got could see that the coils were just being pulled up the hole. The bottom ~3/8" of coil doesn't cover the stud and there was a big gap to the rest of the Heli-Coil stack.

So! Next up is a Time-Sert. (kit 1215) The machine shop agrees that it's the right way to go. That tube (#12159) is only 30mm but should be enough. Maybe I can hack one and get it into the bore lower down. One can hope. If this doesn't work it'll be back to the shop for welding to fill the hole and then drilling/tapping the "fresh" metal.

The ARP studs are all holding great. Those got 90ft-lbs (100 is spec from ARP). With their special lube, lower nut pitch (1.25mm) and new fasteners, the tension on those has got to be huge.

That'll be later this week. I'm going to be optimistic and continue to put the front-end of the block on.
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