Broken 300 head bolt
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Cross-Country
Joined: Nov 2011
Posts: 76
Likes: 13
Broken 300 head bolt
My truck was randomly getting warm and/or puking coolant and it got bad last year so I parked the truck over winter. We pulled the head today and one of the bolts was broken and the gasket was blown in the area near the bolt. The combustion gasses were going into the cooling jacket and blowing the coolant out.
We are going to try removing the broken bolt from the block tomorrow. I am going to try welding a nut to the top and then gently heating the block around the bolt to get it loose. If that doesn't work, it'll have to be drilled/machined out. We'll check the head over tomorrow too.
does anyone know why a head bolt would just break? It looks like it has been broken for a while.
We are going to try removing the broken bolt from the block tomorrow. I am going to try welding a nut to the top and then gently heating the block around the bolt to get it loose. If that doesn't work, it'll have to be drilled/machined out. We'll check the head over tomorrow too.
does anyone know why a head bolt would just break? It looks like it has been broken for a while.
Logistics Pro
Joined: Aug 2014
Posts: 3,558
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If it has been removed before, reusing stock head bolts depending on type, the can be stretched, then break.
there is a term for bolts that cannot be reused, vs bolts that can.
Over torque can break them as well
there is a term for bolts that cannot be reused, vs bolts that can.
Over torque can break them as well
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Cross-Country
Joined: Nov 2011
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Nope. I tapped the bolt with a hammer to loosen it up and then cleaned the top with a grinder. I turned a nut in the lathe to remove the threads and taper the inside for a better weld. I placed a washer over the bolt and then the nut. I welded it in place with high heat and let cool for several minutes to heat soak the block. I had my son heat the block lightly with a torch while I backed the broken bolt out. It ended up being a textbook removal. The hole is fine and the head should be going back on tomorrow after lapping the valves amd replacing the stem seals. The head is warped .002-.003", which is well within spec for this head.
FTE Legend
Joined: Nov 2015
Posts: 30,912
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From: Angier, NC
And as far as I know our truck dont use that type head bolts so they can be reused.
But in your case I would replace them all just to be safe.
You said many layers of gaskets?
WTF who did that and was this the head gasket of intake / exh?
Dave ----
But in your case I would replace them all just to be safe.
You said many layers of gaskets?
WTF who did that and was this the head gasket of intake / exh?
Dave ----
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Cross-Country
Joined: Nov 2011
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We are discussing the head gasket right now. There were at least two distinct layers of gasket residue on the block, plus the stuck pieces from the one I just removed. One was grey and looked like a graphite material, the other had orange in it.
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
was the person that did that 
LOLWonder what else has not been done right
Good luck
Dave ----
Fleet Mechanic
Joined: Nov 2006
Posts: 1,664
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From: Northwest
How bad is the head warped ?
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