Stripped intake bolt hole - Helicoil vs Keensert

[jayfourn8]

I have a 1984 110 that has one of the intake bolts (M6) broke off in the head. I need to drill it out and put a helicoil in but someone before me tried to do the same thing and kind of smeared the hole in a weird way and basically hacked it. I want to use the smallest helicoil possible but I am afraid that there may not be enough meat left there for the helicoil to grab. I planned for the worst and got a stainless KeenSert (much more robust and solid) to throw in there instead which is M10 OD but now I am starting to wonder if the M10 is too large of a diameter for that area of the head. I don’t want to break through and scrap the head.

I was wondering if anyone had ever used this diameter before to fix one of these stripped bolt holes.

Thanks!

[trike savior]

Keen sert also called time cert will likely be too big. Helicoil will be better.
2 thing I have had luck with
Use a Dremel with fiberglass reinforced cutoff wheel. Cut a slot across the middle of the bolt and turn it out with a flathead screwdriver. Don't worry about cutting into gasket surface a bit. It won't effect anything.
After you drill it, thread it a slightly bigger standard size. You can't go next size bigger in metric cause its too big. But you can often find a standard that still fits through intake holes but is bigger.

[jayfourn8]

Thanks for your reply!
So the hole I was dealing with was pretty messed up. The bolt was no longer there, or actually it was but any visible part of it was well below the gasket/mating surface. It looked as if someone used a hand drill to try and drill it out and when they missed or fell off of the axis of the bolt they just grabbed some aluminum to the side of it and tried to side cut the bolt with the drill bit as if it was an end mill. In doing so the hole became so big and elongated that I was pretty sure an M6 Helicoil would not work. It practically dropped right in the hole. I ended up going with the KeenSert which is has an external thread of M10 x 1.25 and internal thread of M6 x 1. I was worried about drilling the M10 pilot drill (11/32) and breaking through but I really had no choice.

Well, all that said, I did drill it out starting with a 2 flute ¼” end mill and then graduating to 5/16 and then to 11/32. I didn’t break through and the insert worked perfectly. I only went about 5/8 down with the M10 pilot.

Ill post some pictures later of my setup.

Hopefully this will help someone out in the future.

[czac]

I fixed a head bolt hone on a car engine by filling it with one of those steel putty type things...then re drilled it, it worked great!

[jayfourn8]

Like JB weld??

I thought I was going to have to do something similar but I got lucky.

[czac]

Like JB weld??

I thought I was going to have to do something similar but I got lucky.

yeah but I think it was some other name... my father in law at the time had a machine shop and gave me the stuff. don't recall the name but it worked great... hell maybe could have just filled the hole with weld if need be... lol glad you got it don't though. this stuff happens to me too, the bolt breaks off in the hole and never seems to break off clean, there's always a hump or something that prevents you from drilling a straight hole into the bolt to extract it. the last time this happened was on my old drill press, I actually bloke off a hardened steel bolt remover in the hole...lol I had to hack the f*** out of the hole to get it out then drill it bigger and re tap it for a bigger bolt! lol it never ends!

[Crazyktmmatt]

Ive fixed a few messed up holes with heli coils. The holes were pretty wallered out. Might drill it and go from there. Can always drill it again,if you need to go to a time sert.