E-Z LOK EZ-329-4 Threaded Inserts for Metal, 1/4-20 Installation Kit, Steel, Black Oxide

I wanted to share my experience with two different products--Heli-Coil vs. E-Z Lok Inserts.The inserts measured 0.43" - 0.45". I used a 10.9 Grade M8-1.25 40 mm Flange Bolt that both big box stores carry. The 10.9 Grade bolt's torque spec. is 26.9 [Dry] Lb-Ft and 20.2 [Wet] Lb-Ft, whereas the 12.9 Grade bolt is 31.4 [Dry] Lb-Ft and 23.6 [Wet] Lb-Ft. Do not think these are hardened bolts. This product was an EPIC fail on the first aluminum scrap part. Wait.I tried the first hole with the supplied stamped 27/64" (0.421875) drill bit actually measured 0.3691", 1/2-13" tap and the M8-1.25 insert. Upon observation, the insert was partially OK, but realized that I over-torqued the bolt shearing the head off--used the M10 torgue spec. I could not remove the insert for closer inspection. However, the threads appeared stripped inside. I went and bought another (2) Flange bolts from (2) different big box store--(1) was 10.9 Grade M8-1.25 Flange bolt with #13 metric socket and another 10.9 Grade M8-1.25 Flange bolt with #10 metric socket. [There were no 12.9 Grade Flange bolts].I grabbed another scrap aluminum, drilled up to 13/32" (0.40625) drill bit, used the same 1/2-13" tap and screwed in the insert. Torqued the first bolt to 30 Lb-Ft and the second one to 40.5 and decided not to push it anymore so that was an EPIC success. Will report back after I drill the existing hole on the engine. Note, I tried the E-Z Heli-Coil on the same first aluminum scrap part and it was an EPIC fail--do not use it on any soft metal like an aluminum. This product is promising.I know that if I obtained the 12.9 Grade Flange bolt, the results will improve. I think the bolt will fail before the insert. If the threads become no good in the future, you will have to use an easy out or drill out the insert just enough to remove it. After the threads of the first insert was stripped. I was able to use the easy out and installed another insert--torqued to 30 Lb.Ft. Did not re-tap the hole. Good luck.Last, the Website does not specify--What are the differences of E-Z LOK EZ-310-M8, E-Z LOK EZ-450-8, and E-Z LOK EZ-650-8?

This saved my English block. Broken bolt deep in the block to where I connect my timing chain cover. Followed the instructions and now the car is back together running these streets.

The kit works as described, but the tap included wasn't able to cut in to cast iron heads. Ended up buying a separate tap with more chamfering and was able to get the job done. Inserts worked as advertised

Used to repair 7/16/14 damaged thread in a cast iron racing head for a sbc. Worked great

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