Small hole in head at bottom of valve cover bolt!

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JG1966

JG1966

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I recently removed my 340 for some work and while going over the heads I noticed a small part of the intake runner on my left head (340 X heads) had been "punched out" along the side wall at the bottom of the valve cover bolt hole. The hole is about the size of a small pea.
I assume somewhere in this head's life someone used a too-long valve cover bolt or something (wasn't me). I have no idea how long it's been like this. When I shine a flashlight into the valve cover bolt hole, the light comes out into the intake runner of the head. I immediately checked all of the other valve cover bolt spots inside both heads and only this one is punched out. I checked down at the valves for the metal that got punched out and it's long gone. How can this be fixed? Can I just put a dab of high temp epoxy? It's not affecting any of the valve cover bolt threads. The photo with the screwdriver, it's a very small screwdriver.
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JG1966 said:
I recently removed my 340 for some work and while going over the heads I noticed a small part of the intake runner on my left head (340 X heads) had been "punched out" along the side wall at the bottom of the valve cover bolt hole.
I assume somewhere in this head's life someone used a too-long valve cover bolt or something (wasn't me). I have no idea how long it's been like this. When I shine a flashlight into the valve cover bolt hole, the light comes out into the intake runner of the head. I immediately checked all of the other valve cover bolt spots inside both heads and only this one is punched out. I checked down at the valves for the metal that got punched out and it's long gone. How can this be fixed? Can I just put a dab of high temp epoxy? It's not affecting any of the valve cover bolt threads. I'm trying to post photos, but I always have a hard time getting photos to post.
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A picture showing what you are talking about would be helpful.
 
JG1966 said:
Sorry. There are photos now. It posted before they downloaded.
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It looks like it's broken out so a extra long bolt was put in and cranked down at one time. I would just use a little sealer and call it good.
 
toolmanmike said:
It looks like it's broken out so a extra long bolt was put in and cranked down at one time. I would just use a little sealer and call it good.
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Thanks Mike. I have no idea how long it's been like that but it's never been an issue that I know of. Do you mean sealer on the valve cover bolt to keep everything inside the head or should I try to seal the hole?
 
JG1966 said:
Thanks Mike. I have no idea how long it's been like that but it's never been an issue that I know of. Do you mean sealer on the valve cover bolt to keep everything inside the head or should I try to seal the hole?
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Just a little sealer on the bolt. Just to prevent a vacuum leak which probably shouldn't be an issue anyway.
 
If you are really worried screw a plug in from the topside until it barely peaks out. Then fill with epoxy or JBW, you will probably have to clean up or re-tap.
 
Mike67 said:
If you are really worried screw a plug in from the topside until it barely peaks out. Then fill with epoxy or JBW, you will probably have to clean up or re-tap.
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Thanks Mike. I just put some JB Weld on it. Seems all good. Maybe it will improve my flow in that cylinder.
 
I don't know how the myth got started that JB Weld is good exposed to gas. It's not. JB Weld is not impervious to gasoline and that's not where you want it. I would switch to valve cover studs. They are neater in appearance and hold the gaskets on when you replace them. Coat that stud with a good coat of red high temp RTV and let it ride.
 
RustyRatRod said:
I don't know how the myth got started that JB Weld is good exposed to gas. It's not. JB Weld is not impervious to gasoline and that's not where you want it. I would switch to valve cover studs. They are neater in appearance and hold the gaskets on when you replace them. Coat that stud with a good coat of red high temp RTV and let it ride.
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Every packaged I've bought said it was oil/gas resistant once cured. I've repaired sever gas tanks over the years and never had an issue.
But that was the reason I said run/thread a plug down the bolt hole then backfill.
 
One other option would be to run a very short allen screw all the way down, Red Loctite in place. Any part that protrudes into the port, grind down & smooth it out with a die grinder or Dremel. That'll leave plenty of the tapped portion for your valve cover bolts/studs.
 
Mike67 said:
Every packaged I've bought said it was oil/gas resistant once cured. I've repaired sever gas tanks over the years and never had an issue.
But that was the reason I said run/thread a plug down the bolt hole then backfill.
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Their packaging has said that for as long as I can remember. That's like saying Alexandra Ocasio Cortez is conservative. It's just not true. You can ask any cylinder head porter who does a lot of it. If it worked well, that's what they would use. It's not.
 
Professor Fate said:
One other option would be to run a very short allen screw all the way down, Red Loctite in place. Any part that protrudes into the port, grind down & smooth it out with a die grinder or Dremel. That'll leave plenty of the tapped portion for your valve cover bolts/studs.
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Now THAT I would endorse. That would be what I would call a permanent repair. ...and a smart idea, too!
 
If the head is off you might want to debut the area so no more tiny fragments of metal can fall off and migrate into the engine.

I know you already put some jb weld on the hole, but from my thinking I would just put sealer on the VC bolt when you reinstall, that way no way for anything else to make it's way into the engine. Did you test fit a VC bolt while the JB was playable? You may have just made the hole shallower than OEM.
 
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RustyRatRod said:
Their packaging has said that for as long as I can remember. That's like saying Alexandra Ocasio Cortez is conservative. It's just not true. You can ask any cylinder head porter who does a lot of it. If it worked well, that's what they would use. It's not.
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Who in their right mind would say that???? Lol!
Like I said I would have done it a little differently but have never had an issue with JBW and gasoline...must be something to their claim.
I have a 3 wheeler that has had a blob on the bottom of the gas tank for about 10 yrs and still no leak.
Not saying JBW is the be all to end all but to each his own.
 
Dana67Dart said:
If the head is off you might want to debut the area so no more tiny fragments of metal can fall off and migrate into the engine.

I know you already put some in weld on the hole, but from my thinking I would just put sealer on the VC bolt when you reinstall, that way no way for anything else to make it's way into the engine. Did you test fit a VC bolt while the JB was playable? You may have just made the hole shallower than OEM.
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Thanks Dana. Some of these guys scared me so I removed all of the JB Weld before it cured. It's back to the way it was. And yes, I checked the valve cover bolt and it went just about all the way down (enough that the valve cover and gasket would more than make up the difference).
 
Mike67 said:
Who in their right mind would say that???? Lol!
Like I said I would have done it a little differently but have never had an issue with JBW and gasoline...must be something to their claim.
I have a 3 wheeler that has had a blob on the bottom of the gas tank for about 10 yrs and still no leak.
Not saying JBW is the be all to end all but to each his own.
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Thanks Mike. I repaired a tiny pinhole leak on the bottom of a gas tank with JB Weld once and it never leaked again. I'm very confident it would hold up, but I'm gonna explore my options. I'm in no hurry. I'm not getting motor back for at least a month
 
Is it just me or do those look ported in an inch or so? looks smooth then goes rough cast.
 
JG1966 said:
Thanks Mike. I repaired a tiny pinhole leak on the bottom of a gas tank with JB Weld once and it never leaked again. I'm very confident it would hold up, but I'm gonna explore my options. I'm in no hurry. I'm not getting motor back for at least a month
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No problem, I think it would have worked also, but again there is more than one way to skin a cat.
There will be many good recommendations, some easy, some quick and some more involved. Pick your poison.
I agree with Dana7 & deburring it with a dremel or a carbide bit. I would measure the length of the hole and figure out how long of a plug you would need and either cut the end of a stainless bolt to length put a notch in it for a small screw driver to set it and JBW the threads.
Best of luck!
 
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