Acorn nut stuck on stud

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Mozenrath

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Jan 13, 2011
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I have finally decided to switch to long hex nuts, but one of the acorn nuts on my head has decided to stick to the stud, and I can't get it off. I can still pull it out with the whole stud, but if I want to replace it with new long hex nut, I'll need to get off that acorn nut.

Any suggestions? :-||
 
2door

2door

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Unthread the stud from the case with the acorn nut still on it. Clamp the stud in a vice and carefully unscrew the acorn off the stud. You might want to repair the threads with a die then reinstall the stud, throw the acorn nuts in the trash and pick up some good quality hex nuts, preferably the shouldered type and use those.
I recommend removing the cylinder head and using two hex nuts, back to back (double nut) and torque the studs into the case (120 to 140 inch pounds) then install the cylinder head and new nuts. Torque them to the same value as you did the studs.

Those pretty chrome acorn nuts are probably responsible for more head gasket and compression loss problems that any other factor. Throw them away.
Good luck.
 
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dawa31

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Sep 25, 2011
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I just got done with the same problem. I used a small pipe wrench to hold the stud bolt wail using a boxed end wrench on the nut it's self. Just be careful not to scar the stud bolt.
 
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Mozenrath

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Well I replaced 3/4 of my nuts on the head. I couldn't get metric hex nuts that were long or shouldered, so I got some normal-sized ones and some appropriately sized washers. Seems to be working out great so far and they seem to actually loosen less from temperature changes than the original acorn nuts. One of my acorn nuts actually stripped! That's why I had no choice but to replace all except the one that's seized on the stud. I don't have a good vice, so I need to find another way to get it off. I really hope I don't jack up the stud, in which case I'll be mighty angry. :mad:
 
Al.Fisherman

Al.Fisherman

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Mozenrath said:
I have finally decided to switch to long hex nuts, but one of the acorn nuts on my head has decided to stick to the stud, and I can't get it off. I can still pull it out with the whole stud, but if I want to replace it with new long hex nut, I'll need to get off that acorn nut.

Any suggestions? :-||
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Mozenrath said:
Well I replaced 3/4 of my nuts on the head. I couldn't get metric hex nuts that were long or shouldered, so I got some normal-sized ones and some appropriately sized washers. Seems to be working out great so far and they seem to actually loosen less from temperature changes than the original acorn nuts. One of my acorn nuts actually stripped! That's why I had no choice but to replace all except the one that's seized on the stud. I don't have a good vice, so I need to find another way to get it off. I really hope I don't jack up the stud, in which case I'll be mighty angry. :mad:
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Sounds like the nut is cross threaded and not stripped. If it is stripped you most likely loose your head gasket. If it is cross threaded, get a socket and pull the nut with the stud out. Hopefully the nut and stud will come out together. GOOD studs and nuts are cheap. Trash them all as they are JUNK. Is it stripped or cross threaded? You mentioned
"stuck" in opening post and now you say "stripped" Big difference. I'm going to assume cross threaded as you mentioned you can pull the stud and nut together.

By the way... How can you "jack" up the stud.
 
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Al.Fisherman

Al.Fisherman

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maintenancenazi said:
^^ I believe " jacked up " is a term to discribe " messed up ".
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I don't know of anyone using that (improper) term. So it's destroyed, stripped or broken. Jacked up is what I do to my vehicle as in changing a tire. Actually, I don't even do that now a days.... I called road service. :>)
 

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Jumpa

Jumpa

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HEAT! Heat removes all stuck nut & Bolts also use a 10 or 14" Stilson to hold the bolt "where there are no threads" Then lay the Stilson and the bolt on the ground , grab box end wrench and it will have no choice however if you do this without the heat chances are the stud will break
 
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maintenancenazi

maintenancenazi

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Al.Fisherman said:
I don't know of anyone using that (improper) term. So it's destroyed, stripped or broken. Jacked up is what I do to my vehicle as in changing a tire. Actually, I don't even do that now a days.... I called road service. :>)
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Well no, it's NOT a correct term. It's just more of what is considered modern slang. I personally have never used this term myself, I was just clarifying it's meaning.
 
BarelyAWake

BarelyAWake

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Actually, it's a commonplace term in many areas... does no one ever look these things up? Urban Dictionary: jacked up

Given this is an international forum, I believe petty details like the "correctness" of regional slang and it's derivatives can be over looked for the content.
 
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Mozenrath

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Haha, I should have thought not to use that term in a forum where people are likely to deal with vehicles. I don't know if it's a regional or generational term, but I and others I know in real life use it on occasion. No, I do not mean that I literally used a jack on a nut/stud.

The acorn nut that got stripped is not the one that is stuck. It's just another one which I already replaced.

Yes, I've tried heat. Didn't work. I could try making it cherry-red hot, but again, I'm not sure if that will compromise the integrity of the stud.

I just need to get something that will hold the stud in place so I can twist off the stuck nut. Unfortunately, I don't own a vice.
 
2door

2door

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It's been my experience with the acorn nuts that they bottom out and distort the threads at the end of the stud. Due to inconsistancies of stud length, or how far they are screwed into the case, the acorn can tighten against the top of the stud if there's too much thread protruding from the cyclinder head. When this happens not only can the nut jamb on the stud but it isn't tightening the head against the gasket correctly.

Earlier, in a previous post I suggested you remove the cylinder head by removing the four nuts or in the case of the jambed one, the nut and the stud.
Several people have suggested alternatives to a vice; pipe wrench, vice grips, etc. A little scaring of the smooth portion of the stud won't matter, just protect the threads. A word of caution here; overheating can cause the metal parts to gall together making it harder to get them apart. Hold the stud by whatever means available to you, use a box end wrench on the acorn nut and force it off. A little back and forth action might help. like rocking a car out of the mud. You'll probably find the threads damaged a little, especially on the very end of the stud. These can be rejuvinated with the proper size/pitch threading die available at most hardware stores. It's probably an 8mm X 1 or possibly 8mm X 1.25
Or, you can order a new stud/s from one of the suppliers that sponsor here.

Just don't 'jack up' anything :)

Tom
 
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Al.Fisherman

Al.Fisherman

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Dave31 said:
Use a nut splitter or hacksaw and cut the nut off...
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Kind or hard to with the cylinder head installed.

Most likely the head nut is a 14mm, for 8mm studs, and a 10mm for 6mm studs (found on some 49cc engines). Take a correct socket and a breaker bar/ratchet (1/2" best but a 3/8" will work, breaker bar is best). Just unscrew the nut..one of two things will happen. 1) the nut will come off, or 2) the nut and stud will come loose. Trash studs and nuts, buy a Metric 8.8 hardware and run a tap to clean threads. Install new hardware and torque to specifications. Like Tom said 6mm are 1.0 thread, 8mm are 1.25 (most common) thread and the uncommon 8mm 1.0 thread.
 
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D

dawa31

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Sep 25, 2011
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Jumpa said:
HEAT! Heat removes all stuck nut & Bolts also use a 10 or 14" Stilson to hold the bolt "where there are no threads" Then lay the Stilson and the bolt on the ground , grab box end wrench and it will have no choice however if you do this without the heat chances are the stud will break
Click to expand...
I'm shore this is like a pipe wrench, just never heard it called a Stilon? Or is it more like a vice grip wrench?
 
rohmell

rohmell

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Jun 2, 2010
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I have found that these engines don't have the stud holes in the engine case halves threaded completely to the bottom of the hole. By running a bottoming tap into these holes and finishing the job that the Chinese started, the studs will go into the halves a little bit more, and the problem of the stud hitting the domed roof of the acorn nut before being fully tightened down will be eliminated.
 
2door

2door

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Rohmell,
That's true in some cases but I've also found studs of different lengths in the same engine. I've seen them as much as 1/4" difference in length. Common sense says to check this situation prior to torquing the head down the first time but, well, you know. Not everyone is going to do that.
Tom
 
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