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What is an acceptable fix for a crack in the head stud boss area . ? .. The crack is vertical and inline with the stud, about 1/4 inch long. I have been told a small hole can be drilled at the bottom of the crack to relieve stress and help prevent the crack from spreading further. Is this alone enough to take care of the problem. ? .. Should the crack be brazed, also .. ? ..
What is an acceptable fix for a crack in the head stud boss area . ? .. The crack is vertical and inline with the stud, about 1/4 inch long. I have been told a small hole can be drilled at the bottom of the crack to relieve stress and help prevent the crack from spreading further. Is this alone enough to take care of the problem. ? .. Should the crack be brazed, also .. ? ..
John
Sounds like somebody drove in an oversize stud without reaming the hole first. Go ahead and drill the hole at the end of the crack and then drop down about a 1/4" and drill through the embossment and through the stud and drive in an expansion pin.
I happen to have first hand knowledge from years ago.
The crack exists in the rocker arm stud, yes. The rocker arm studs are the straight shank threaded type, sans hex base. Thanks for your reply, Mike.
I didn't realize you had screw in studs until now. I assumed you were talking press in studs.
If the embossment got cracked during the tapping operation due to the hole not being large enough for the tap the expansion pin would probably work okay. If the emboss cracked after it has been tapped all the way down then you could assume the threaded hole is probably enlarged. I'm not sure the stud wouldn't work in the hole and eventually pull.
Sometimes when you weld cast iron, it will crack right beside the weld.
What about brazing the crack? Is that ok to do in this instance.? .. IIRC, brazing is more a form of hard soldering than welding? . .Thanks, Mike
I'm not sure of the extent of your damage over the keyboard. How about this: If the stud is not tight in the embossment, remove it, braze it, drill it oversize and install a heli-coil and screw your stud back in. Otherwise, take the first suggestion of drilling and pinning. Best I can do without seeing it.
I am going through this problem. I drove a new pressed-in rocker arm stud into the stud boss. The stud boss is now cracked on one side. My plan is to drill a 5/32 inch hole through the stud boss and stud so that the drilled hole intersects the end of the crack. I will then insert a pin through the boss and stud. I am hoping that does two things: (1) stops the crack; and (2) anchors the rocker arm stud.
My plan is to drill a 5/32 inch hole through the stud boss and stud so that the drilled hole intersects the end of the crack. I will then insert a pin through the boss and stud. I am hoping that does two things: (1) stops the crack; and (2) anchors the rocker arm stud.
Thoughts?[/QUOTE]
I would drill and pin 90* to the embossment crack.
If you cracked it driving a new stud in I would guess you used a .003" oversize stud. I've never seen a stock stud crack one. The best way to repair it would be to cut the boss down and install screw in studs if the machining will remove all of the crack. Option 2 is a screw in stud that doesn't have a nut made on it. It looks like a normal stud installed. Your main concern here is these studs have a taper where the threads end. You cannot just jamb them in they will split a good stud boss. You could lock title the stud and snug it in. These studs go into the water jacket. Pinning it might work but it wouldn't be the way I would approach it. Hurry up and read this before this thread gets locked. Good luck. Pioneer makes the studs by the way.
If you cracked it driving a new stud in I would guess you used a .003" oversize stud. I've never seen a stock stud crack on. The best way to repair it would be to cut the boss down and install screw in studs if the machining will remove all of the crack. Option 2 is a screw in stud that doesn't have a nut made on it. It looks like a normal stud installed. Your main concern here is these studs have a taper where the threads end. You cannot just jamb them in they will split a good stud boss. You could lock title the stud and snug it in. These studs go into the water jacket. Pinning it might work but it wouldn't be the way I would approach it. Hurry up and read this before this thread gets locked. Good luck. Pioneer makes the studs by the way.
In defense of the drilling/pinning.
50+ years ago, I changed one stud out for what reason I don't remember. The first size replacement was .003 OS. I didn't have a reamer. Didn't think I needed one just for that little bit. Tapped the new stud and presto! Cracked stud boss.
Here it is, 50 plus years later and the same stud is still in place, no pin, no nothing. L 79 engine. Run hard.
Maybe I just got lucky?
If the pinning doesn't hold, the OP has lost nothing. He can always put in a threaded stud.
So what. The prior information is sill valid. Would you rather that virtue4u had started a new thread. Give him credit for having searched the forum for a relevant thread and adding his planned actions to build on what has already been said.
All of the early small block Chevy heads came with pressed in rocker studs, including all of the hp and shp engines. It wasn't uncommon back then to have a stud work loose when the engines were being rung out rpm wise. The easiest solution was to press the stud (or a new one) back in the head and drill the boss/stud for a pin and pin them to retain the stud. Often a permanent solution.
Then screw in studs came along and could be used to replace the pressed in stud by simply drilling and tapping the boss in the head for the screw in stud. This could sometimes be down without removing the head and offered a more permanent solution. The draw back was that these studs had a small collar the stopped the stud from being screwed into the head too far. Unfortunately if it was screwed in just a bit too far, the collar could act as a wedge and split/crack the stud boss in the head.
A better, and safer solution was to use the rocker arm stud with the machined hex on it. This can be screwed into the head easily with much less risk of damaging a stud boss. It does however require milling the standard stud boss to provide additional clearance between the rocker arm and the hex portion of the stud. Depending on how far a crack in a damaged stud goes, it is sometime possible to machine to below the crack and eliminate this weakness without having to weld it. Most aftermarket heads come machined to utilize these types of studs.
I'm not sure of the extent of your damage over the keyboard. How about this: If the stud is not tight in the embossment, remove it, braze it, drill it oversize and install a heli-coil and screw your stud back in. Otherwise, take the first suggestion of drilling and pinning. Best I can do without seeing it.
Have an old Massey-Ferguson 150 farm tractor. It's for work; not show. Lots of heavy american cast iron. Brake pedal is a heavy casting also. Everything has a cycle life. After x many times of letting iron pedal spring back against its steel stop, pedal snapped in-two. Left it at commercial welding shop and they brazed it (heck I could've done that). It didn't last but a few strokes and it snapped right at where it was brazed. The brazing did Not "weld" or "meld" the two parted pieces into one-another ... brazing did Not penetrate as a real weld will. For about 30 minutes I'd begun to think of of bringing those clowns an sbc 400 block with a horizontal crack (into jacket) running along outside of one deck. On second thought, NO! I took the M-F pedal to another shop who properly welded the cast iron. Never another pedal issue. They didn't have a large oven to put block in so it's still a big paperweight. Used to be a guy in Darlington who did but he's gone.
I haven't thought about any of this in years until this thread considering brazing rocker boss.
Good luck on brazed stud boss.
Again, unless that head is something special or rare, I'd look for another.
Again, unless that head is something special or rare, I'd look for another.
What you were trying to do with brass on that clutch pedal could have been done a lot easier and cheaper with a couple of squirts of Elmer's Wood glue and you'd have gotten about the same results.
What you were trying to do with brass on that clutch pedal could have been done a lot easier and cheaper with a couple of squirts of Elmer's Wood glue and you'd have gotten about the same results.
No ... what were THEY thinking? When I dropped it off, I thought they were going to weld it. I could've brazed it myself.
11-03-2005, 11:05 AM
stud boss crack
Tapped the new stud and presto! Cracked stud boss.
