Hi folks, You've all been so helpful in the past, i hope you don't mind giving this some thought. My buddy is having trouble with the engine in his car. This car pulls his bike trailer, so it is remotely bike related. Any feedback is greatly appreciated. Here is his latest report: I got the easy out and broken bolt out of my block and drilled a 1/2" hole for the helicoil. Then, realized that the machinist at Carquest sold me the wrong size helocoil. He supposedly measured my bolt and told me it was 1/2" diameter and it is really 12mm. Why I am asking......... I called around and asked if I should try to put the 12mm helicoil in a 1/2" hole. The helicoil I have goes in a 31/64 hole and I bored a 32/64" (1/2") hole. Is 1/64, (0.016) of an inch too big of a hole that big a deal? If I go with a helicoil in the existing block...............If the helicoil withstands the 100lbs of torque. Is that the test? OR, will running the engine, heat, compression, Turbo boost, etc,,,,,,,be the real test. In other words, will it fail on my garage floor under torque wrench load or will it fail after I install it and start the engine under gas pedal load? Again, many thanks!
shouldn't be a problem, looks like you will still have around 60% of thread, ideal is 65-80%.i wouldn't have any problem doing it, and i have installed hundreds(maintenance machinist for 13+ years)
what is the bolt for? head bolt, turbo mount, etc? to me, .016 too big would be a little sloppy for something with that much torque on it. why not put the regular 1/2" helicoil in and get a single 1/2" bolt for that one hole? i hate mismatchd bolt sizes, but at least you know it'll hold. or find something else to put a helicoil in to see how the threads are before doing it on the real thing.
It will be fine. The reason being is the Helicoil, being a bigger diameter than the original thread, will still have more thread area than the original including the 0.0075 missing per side. The pullout for a helicoil is more than that required to strip the threads on the bolt barring corrosion or galled threads.
