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Broken head bolt 80 15hp johnson can i helicoil it?

poida

Contributing Member
Bugger, i just snapped a head bolt off and don't have much to grab with vice grips.
Can i use an arc welder to weld to it then lean on it again with heat and penetrol? Not sure if its stainless or not.
I think it is stuck in there properly though so am leaning to grinding it flush and drilling it out. Can a helicoil take the torque/load of a head bolt?
I don't want to take it to a machine shop so it will become a parts motor othewise.
Does anyone know the thread eg 1/4 unc so i can order a helicoil kit?
 
A properly installed HeliCoil is just fine. Actually stronger than the original. No, they are not stainless steel and I am reasonably sure they are 5/16 coarse head bolts. More than likely a different thread length than standard though. Check one of the other ones to verify that.
 
Had a sleep on the problem and i think i will put a nut bigger than the stud over it and give it a good zap with the welder. Then i can lean on it again and get the block nice and warm at the same time with a torch. I am toying with the idea of drilling in the side of the block to get some lube on the threads/release tension on the threads. This bolt had slightly cracked the outside of the head which has probably added a corrosion problem on this bolt.
I really don't want to split the block to set it up in a drill press though so hope the above works.
I had one exhaust cover bolt that did the same thing. It may have been luck but i drilled straight down the middle (hand drilled) of it then filled it with atf fluid. After weeks of heating it up and leaning on it i drilled it out to pretty much the diameter of the inner threads, this sucker was never going to budge and managed to pick a few threads out. I then had the bad idea of running a tap down which then got stuck pretty much at the bottom and i snapped it off. I should have just cleared half the hole and it would have been fine. End result i have heli coiled it and will use a shorter bolt.
Any thoughts on again hand drilling out a head bolt?
 
Broke loosening it up.
If i weld it it might snap deeper makeing it hard to drill centre of this bolt. I'll have a look for reverse drill bits, never seen them before.
Think ill give the welder a go.
"I wouldnt apply too much heat as aluminum has no memory." Not sure what you mean by this??? Might i melt it?
 
Well I see you learned the first lesson--NEVER put a tap into a hole that still has fragments of the old bolt in it. Second lesson should be NEVER try to get the broken bolt out with an Easy-Out. There is no such thing, it ain't easy and it won't get it out. After all, if the bolt wasn't strong enough to turn itself out, why would a skinny, fragile Easy-Out be?

Anyway, I think you are on the right track, if you can weld a nut on it, then heat the aluminum along the length of the bolt. You cannot get I too hot unless you melt it. Oherwise, the hotter the better.

BW, the aluminum, is split along the bolt because corrosion inside has expanded and busted it.

You ask if anybody has drilled them by hand. I have. Thousands of them in my 24 years working every day in the outboard shop alongside the Gulf Of Mexico (salt water). It is a skill learned only by doing. I'm still learning. Every one is still a challenge.
 
Yep, tapping a hole with fragments in it did not work, should have just tapped 3/4 of the hole though and would have got away with it. And yes standard easy outs are a waste of time on stuck bolts, the splined ones without a taper can give you some joy though.
I did weld a nut on it and gave it some heat. The bolt sheared off way too easily so the bolt must have been comprimised by the previous break.
It gave me just enough above the block to grind it flat, the next job will be to hand drill it, fingers crossed.
I'll invest in some left hand drill bits in the hope that it will wind out.
The bolt obviosly has more threads and reach into the block than the heli coil. Is there a special "long" helicoil or can i wind 2 in or will a standard on suffice???
 
^^^ yep tried atf fluid for weeks on the exhaust cover bolt, did not achieve anything for me, that sucker was stuck tight. Looked really good heating it up watching the atf fluid bubble around the snapped bolt. Could have heli coiled it in half an hour if i didn't stuff around with a tap.
 
You may be able to put two heli-coils in it, if you leave space enough between them to break off the tang on the inner one. However, that is not necessary. You only need one diameter in length. In other words, a 5/16" thread needs 5/16" thread engagement. I learned that directly from an engineer.
 
Righto if i am going to by a specific set of bits to drill bolts/studs etc what should i go for? Cobolt?
 
I do suggest cobalt for drilling stainless steel bolts. They also are good for steel. Speaking of stainless, that is a whole different topic. That stuff work hardens as you cut it.
 
I have a lh set of bits comming from the states. I thought i would put the pilot hole down and soak in acetone and atf fluid. First problem.
Centre punch did not mark the stud, it just flattened the centre punch. I sharpened it but these bolts are tough.
Tried with a few drill bits but no one bit of metal got drilled.
I'd like to avoid splitting the crankcase to put in the drill press but i might have to. Any suggestions on how to centre punch and drill?
 
I split the block, put it in the drill press and bluntened a handful of cheap bits but at least made a small centring mark in the stud. I managed to get the press to spin in reverse and tried the lh bits. Not a thing, nothing, unless someone has any suggestions this is going to become a boat anchor. Can not believe how hard this stud is, its harder than a centre punch and drill bits.
 
Yes it is possible that welding hardened it. There is one last ditch thing you can do if / when all else fails. Cut the aluminum away along the length of one side of the bolt and take the bolt out sideways. Then have the aluminum welded back in and re-drill and tap it. I've done that where customers have busted off drills and taps in the bolt.
 
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