JB weld strong enough?

[mellowyellow#7933]

Well, managed to break off valve cover bolt in head. After breaking off an easy out and 2 drill bits INSIDE my perfectly drilled hole I had to drill it all out with progressively larger drill bits. Now I have a huge hole, not quite centered anymore. May have to drill even more to centre. If I fill hole with JB weld, will it be strong enough to just tap to accept cover bolt alone or hold a heli-coil in place(maybe with some blue loctite also?)? Have no experience with heli-coils but I saw on the web you can get double coils for bigger holes. My thought is it would be easier to align hole using JB weld on it's own or with a single heli-coil than drilling more out for double coil. Hole is currently more than 1/4 inch, bolt is 6mm x 1. pitch. What size heli-coil/drill bit to use?
Anyone have any better ideas other than removing head & having it welded & re-tapped?

[DFragn]

Ouch, I've drilled and tapped JB Weld for a smaller thread size then the valve cover bolts. But this was for an IS Pod screw in the radiator bracket. And, over time, it's loosening up. But, holds well enough for a accessory mount.

Valve cover bolt torque is only 9 lbs.. It could work as a temporary fix. But you could end up with crunchy pieces of JB Weld in your oil and running through your engine.
I wouldn't do it.

I don't know if a heli-coil large enough to secure in your opening would have a small enough I.D. for the bolt
Best repair would be to have it filled professionally with aluminum & re-tapped.
Might be better to pull the head to have it filled to keep any crap from getting in the engine oil and finding a happy home amidst your piston rings or some inopportune location.

Not my field of expertise, just my thoughts.

[Chrisj CMA]

I think the real fix (unfortunately for you) is to take the head and the valve cover to a machine shop and have the hole welded and re tapped.  

BUT

Depending on how "HUGE" that hole is.....If you could manage to JB weld a steel threaded bushing inside there for the new valve cover bolt to thread into I think JB Weld would hold in that manner (not that its a very "correct" fix) but may be worth trying.

Obviously you have found that these bolts dont get much torque.......you carefullt tighten until it hits the hard stop and then just a tic more to keep it from backing out

[BigM]

Check your auto parts store. There is something, can't remember the name , epoxy that will set up hard enough to were you can drill it, and retap.

[larryh0841]

I tried to reply earlier but it did not go through.  One fix you can do at home is to drill and tap the messed up hole for a standard size bolt.  Plug the hole with a standard sized aluminum bolt being sure to bottom the plug in the tapped hole so it does not come loose.  Cut the plug off and file it back flush to the mounting surface.  Then drill and tap the plug back to the original size for the valve cover screw.  By using this method you do not have to worry about getting the messed up hole back on center as this will work even if the valve cover hole cuts through the side of the plug.  Just be sure that you bottom the plug in the hole and it is deeper than the valve cover screw hole that you will be drilling.

[John Schmidt]

If you have a broken bolt larger than a nail, don't even bother with East Outs, you'll break them nearly every time. Invest in a set of the item in the link below, has saved my bacon a few times on old equipment with rusted in studs, bolts, etc.


http://www.sears.com/shc/s/p_10153_12605_00952157000P?prdNo=18&blockNo=18&blockType=G18#desc

[Ricky-D]

It may not be necessary to do all that!

if oil doesn't leak with the bolt missing you could simply use some JB weld on the inside of the cover to hold the bolt head in place and go without all that stuff!

Jus sayin'

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[Redline +]

I tried to reply earlier but it did not go through.  One fix you can do at home is to drill and tap the messed up hole for a standard size bolt.  Plug the hole with a standard sized aluminum bolt being sure to bottom the plug in the tapped hole so it does not come loose.  Cut the plug off and file it back flush to the mounting surface.  Then drill and tap the plug back to the original size for the valve cover screw.  By using this method you do not have to worry about getting the messed up hole back on center as this will work even if the valve cover hole cuts through the side of the plug.  Just be sure that you bottom the plug in the hole and it is deeper than the valve cover screw hole that you will be drilling.

Short of removing the head, welding, machine, drill and tap this is your best option. There are also threaded tapered aluminum plugs available. These are designed for crack repair and might be available from your local automotive machinist.

Redline 

[art]

larryho841 has it right.I've been a machinist for 50 years an that is what I would do .No thread replacements just drill an tap an plug with a bigger alum. plug an redrill an tap on center with the proper size.It will be just like new.Don't be afraid to pull the head.If you have ever done auto repair the valk is easy

[chip]

The worst part of the story here I see is ( not quite centered anymore ) You may need to remove the head, find the correct location for the broken bolt, and use an end mill to plunge into  the correct location. Trying to redrill and tap for a bushing or a heli-coil may be a problem, a drill will tend to follow the path of lest resistance ,which would be the hole that's "not quite on center anymore". Any competent machine shop with a Bridgeport type mill should be able to do the job.

[Walküre]

Also agree with Larry - I would add one thing - try to find a "bottoming tap" for the hole - that's a flat-bottomed tap, that takes the threads down to the bottom of the hole, because you REALLY want the aluminum bolt to bottom out, not just go to the taper, that a normal tap leaves.

Also, try to find an appropriate "transfer punch" - that's a punch just an RCH smaller than the hole in the valve cover - and put the valve cover on with the rest of the bolts (after putting your aluminum "plug" in place). then, use the transfer punch to make sure your NEW hole is exactly centered.

sometimes this stuff is so easy, a 4 year old can do it......with 20 years experience!!   

Good luck, let us know how it turns out.

R

[YoungPUP]

?heres my 2 cents worth. it may be worth a chat with your local Fastenal store.  Have found on more than one occasion that they have or can get threaded inserts for MANY applications. May have to take a small pack 10-20 but may be cheaper than all the machine work... Good luck

[mellowyellow#7933]

Filled the hole with JB weld & left it for a couple days. Drilled & tapped, bolt threaded in but wouldn't hold when torqued. Couldn't find any aluminum bolts in town as Larry sugested (thanks Larry) so bought a 3' length of 3/8" aluminum rod & ran it through the die, cut a short piece & notched it with Dremmel, drilled out all the JB weld & tapped the hole, inserted the threaded rod with locktite & re-tapped to correct size. Just waiting for the rain to end to take it on a good run to make sure it stays put.
Thanks for all the suggestions.

[Ricky-D]

Since it's only a cover I would say again that the torque may not be necessary.

There are still five bolts to hold the cover tight and the six maybe only needs to fill in the empty hole in the cover.

If you could thread the JB and screw in the bolt, well, that may have been all you needed to do!

It doesn't hurt to try and see if no oil will leak.

There may come a time where you may have to remove the head and at that time I would suggest that the operation previously mentioned would become cogent.

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