The Stovebolt Site Forums The Shop Area Engine Shop Any Machinists In The House? (Broken Bolt Issue)

I inherited this problem. The last guy said he pulled this engine because he couldn't get it to stop leaking oil. Well, I think I found the problem. The front bolt on the valve cover, drivers side, is really messed up. I put a stud in it with some sealer because I saw that the threads were worn. Today, about 10 minutes into cam break-in, it starts to leak a little oil. So, of course, I try to tighten it. It pulls through the threads and pours on the header. Uhg! I tore it down this evening and cleaned out the hole. It's enormous! Uhg again! The kicker may be that it has something very hard at the bottom of the hole. It knocks the point off my punch and a drill bit won't bite at all.

I think I have a nickel rod or two around from a block repair I did a few years ago. Not sure I could weld that hole shut and start over though.

Any thoughts or suggestions are greatly appreciated.

Don't even think about welding it. Whatever is imbedded in the bottom of the hole is going to have to come out. It's probably a piece of a drill bit, or maybe an EZ-out. I'd suggest using a die grinder and a diamond burr to try to dislodge whatever is down there, and then using the same type of tool to get the hole round enough to thread it for a plug, then drill and tap the plug for the proper stud. If I had the engine in my shop, I'd remove the head and use a drill press or a Bridgeport mill to mimimize the risk of making the situation worse. That head is fixable, but just barely!
Jerry

I was afraid of that. I am supposed to have this thing done by the 8th, which is the owners 81st Birthday. Uhg!

I've been digging around in it with a pick. Looks like the flutes are straight on whatever is in there. My guess is a tap. Lucky me!

I've got an appointment at the exhaust shop tomorrow. I may through it back together, just to keep that on schedule, then start pulling my hair out Friday.

I have salvaged a few "OOPS" situations with broken taps with a variable speed Dremel tool and this type of diamond burr, but it's a S-- - -L- - - - -O- - - -W process. Be very patient so you don't make things a lot worse. Good luck!

www.ebay.com/itm/404420961535?

Jerry

Another approach, similar to HRL, that hole is pretty large and you should be able to get in there with a small round head die grinder bit or dremel tool and grind almost straight down to grind out whatever that is that is in there. Then drill the hole out to a larger tap size for a bolt, tap the hole with a bottom tap for threads. Use some red loctite and install a bolt. Cut the bolt head off, leave some material proud of the hole, center punch it, drill it to the correct size for the valve cover screw, tap the threads, then cut and grind it flush to the head, a small chamfer and maybe just a quick clean out of the threads with the tap.

With the right cutting tool removing taps is easy. Looks to me up to a 1/2" bolt would be suitable for the repair Dragsix suggests but I only have 848 heads to look at. Be cautious with depth...on the right side of the last picture you can see the bolt boss from the inside. Too deep and you may hit water. Good luck.

These are some great ideas! I think it may have to come off to fix it right. I'm distraught over that. I was trying hard to deliver this weekend.

This is the 880 head I believe.

Dragsix - I like your approach. I always used a Heli-coil if one were available; and if not made my own. Your approach might be easier than making my own thread insert on odd threads.

If one has a milling machine of sufficient size, a carbide-tipped end mill works pretty well to remove the obstruction.

Jon

Once you get the hard center dislodged, drill and tap the hole for a cast iron pipe plug- - - -most likely a 3/8 NPT. Install the plug with red LocTite to seal any potential coolant leaks, grind it flush with the top of the head, and then drill and tap it for the correct valve cover bolt (1/4-20). That's similar to the type of plug repair done for a crack in a head or block. No problems that way with heat expansion with a plug made from a steel bolt VS a cast iron head.
Jerry

Not as easy on a manual machine but I used to remove small broken taps on a CNC machine using a 4 flute carbide end mill with no coolant and spun it up pretty fast, and did a .010 peck, it took awhile but worked great. Yeah ruins the end mill but worked.
I'd go with Jerry's fix, good idea cast iron pipe plug.

If the flutes on the tap aren't plugged with material, a tap extractor tool might work. A tool with fingers that go inside the flutes of the tap to back it out of the hole.
Similar to THIS.
The worst that can happen is the finger on the tool break off in the tap flutes.

Surprised no one said anything about an EDM approach. When set up right, it will burn that tap out with no further damage to the hole in just a couple minutes. Then plug it like Jerry said and retap it. An EDM is one of those tools that are not cheap and used very little. But when you need one, they work really slick.

Don

EDM? New to me, Don. But then again, what isn't? Anyway, can you explain? Might be worth looking into. I've been dealing with a lot of snapped bolts at wotk lately and could stand exposure to a better approach.

Interesting that one of the first uses for EDM was removing broken drills and taps.

LINK

John, just do a search on u-tube “broken tap removal using an EDM machine”, there are plenty of how to videos on how it works.
It I’d basically just an electrode that burns the tap/bolt out without doing any damage to the threads.
When set up right, it works really slick.

Don

Edit: Wow Kevin, I knew they have been around a long time, but not that long!

Electronic Dance Music

Ya, that heavy bass thumping will vibrate the broken bit right out of there, especially some Jamaican Dub!

For reference I threaded a 3/8” NPT tap into a fitting hand tight and the depth engagement is 5/8”. Even with a shortened tap this is mighty invasive in that location. As for EDM its crazy slow and expensive for me when I need it. A 1/8” drill costing $5 broken deep in a part can cost me $600 to remove so even slightly worn tools are relieved of duty. Solenoid housings in the last picture require 17 press fit expansion plugs to direct hydraulic flow.

John, I don't think they make an EDM machine big enough to fit one of those excavators you work on into the fluid it needs to submerge the electrode. Unless things have changed a lot since we got an EDM at the high school machine shop next door to the auto shop I ran for 20-something years, the part has to be immersed in a vat of non-conductive liquid. Ours was set up to cut a 5-pointed star shape through a piece of 1 inch thick steel plate- - - - -pretty impressive!
Jerry

I don't think I'm going to splurge on an EDM at the moment. The kind fellow I bought this engine from also does all of my head work. He has a nice little machine shop and thinks he can repair it. I'll post up some winning photos or some awful failure pics soon.

Jerry, how long would it take to burn thru that 1” plate?
10 minutes?

Don

It was a pretty lengthy process. There was a range of feeds, depending on how smooth the finished cut needed to be. The machine we had was purchased in the late 1970s, so it was nowhere near as sophisticated as more modern ones are these days.
Jerry

I used one back in the 90’s trying to extract a broken manhole cover stud on a nuclear steam generator and it was a portable unit and no fluid was required. We did a mock up before the job which worked great but when we did the actual job, the HP’s (health physics tech’s) wrapped the machine up covering the air flow cooling louvers (trying to protect the machine from contamination), it fried the machine before we made much progress.

One of out more talented welders flushed the stud out with a OA torch.

I see a smaller example of one on eBay which is fairly reasonable. Here is a link.

Some Videos on how they work.

www.youtube.com/watch?v=YbeKxFBZrF8

www.youtube.com/watch?v=VFFOKtCcNFs

Did they up your dose limits for that job Phil?
Or just tell you to stay out of the shine?

Don

HMMMMMMM- - - - - -I wonder if one of those machines could be used to put oil galleries into a 216 crankshaft for full pressure lubrication? Or maybe just make a 1/8" pilot hole to follow with a deep hole drill bit?
Jerry

The electrodes are cheap enough Jerry. You could set it up in a lathe and burn it thru with the electrodes. Just make sure you don't get any arcing across the lathe bearings.
As I remember, we just used regular tap water as a flushing fluid.

https://www.ebay.com/itm/385274961983
Don

Some of those oil galleries from the main bearing journal to the rod journal are six inches long or more. I believe it might be necessary to make up a non-conductive guide fixture from something like Bakelite or Teflon to aim the electrode accurately, and then make a mounting jig for the electrode holder. I discussed the procedure with the owner of King's Crankasafts in North Carolina when I bought one of his retired manual crankshaft grinders a few years ago, about drilling the galleries with one of the CNC mills he uses now. He said the first one would be E$$$PENSIVE, as it would include programming the machine, but the cost for duplicates would be much less. This guy makes custom ordered NASCAR crankshafts from solid steel billets, so his idea of "less costly" might still make a restorer's checkbook need CPR!
Jerry

I spent three days fooling with that burnt out machine. Dodging the zoomies as much as I could but still managed to pick up a substantial exposure. Yes they did increase my limits.

Got the head back from my friend. He did a pretty good job and turned it around in 24 hours. He used a Bridgeport and three cutters. It kept tearing up the cutters. Anyhow, the head is back on and it's running again. Woohoo!

Good to hear. You may make that April 8th deadline. thanks for the follow up.

Jerry, some of the pieces of an excavator, though ... The last broken bolt was in a hydraulic motor casing (drive motor) on the skid steer. Smaller piece than the one on the video. But removing it and getting it on the machine would have been a lot more trouble than just doing it the "hard way."

Anyway, interesting video but he needs to invest in a tripod ...

No kidding! It was like watching The Blair Witch Project.

I was a machinist at a CAT dealer for my last 15 years of working. They NEVER had us work on removing a broken bolt until they broke a drill bit, easy out or a tap in the hole! A carbide burr bit is the best way to remove these with out enlarging the hole any more the needed. It has to come out to repair the hole with a heilcoil or thread sleeve if the hole gets to large. Jerry's right, keep the welder away from it!

John, how are those Rube Goldberg drill guides holding up? I can make more if you've managed to wear the first set out.
Jerry

Jerry -- So far, so good! They've saved the day on several repair so far. The last one, though ... Before we could put your savers to it, they went at it with the gas wrench and ended up destroying the o-ring ... now we have to check the oil level everyday on that hydraulic motor before we use the skid steer.

Oh well ...