Continuation from stuck engine thread< Now what>
 

If it wasn't for bad luck,,,,, I put the head on and torqued down the very slowly at 10 pounds at a time until it reached 55 pounds of torque. I moved on to install the carburetor. Went to my tool box to grab a wrench and heard this loud bang. At first I thought my shop light fell on the floor, I looked around a couldn't find anything that dropped. Hmm, What the heck was that noise. So back to the carburetor install. I just happen to glance up and seen number 7 head stud laying on top of the block. My heart just about fell out of my chest. It just happened to be the stud that I was unable to get out right in the center of the two bad cylinders. I called every machine shop in my area and no one will pill the broken stud with the engine in the car. This job just went from fun to real work.

Re: Continuation from stuck engine thread< Now what>
 

Drill it out and tap for an oversize stud?


https://www.snydersantiqueauto.com/P...earchByKeyword


Apparently you don't need to go oversize with that kit above.

Re: Continuation from stuck engine thread< Now what>
 

I'm surprised that it didn't break when you were trying to remove it.

Re: Continuation from stuck engine thread< Now what>
 

I think i'm going to go play the lottery tonight. I really didn't have much faith that it would work but there was about about a 1/4 inch of the stud sticking out of the block. I took my brazing torch and with very low heat I held the tip of the torch right on top the broken tip and just let it stay a nice bright red for a few moments and then grabbed it with my vice gripes and worked it very slowly back and fourth until it started to move and when it started to loosen up I was able to get it out.

Re: Continuation from stuck engine thread< Now what>
 

Nice to hear that you got it out w/out a lot of grief.

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I vote for this. Take a look at the size of the drill. You may find it's "big" by a small amount and will, technically, drill beyond the root diameter of the thread.

Threads in the block are 7/16-14NC. Thread root diameter is 0.3499. Pilot drill size for 75% thread (aluminum, brass, plastic) is No. U or 0.3680. Pilot drill size for 50% thread (steel, stainless, iron) is 25/64 or 0.3906.

The reason the tap drill is larger than the thread root diameter is that it is VERY difficult to tap 100 percent to the thread form. Lots of broken taps have occurred until machinists and engineers settled on the "percent threadform" guidelines above.

Using this kit you use the head as your guide. There is some "free play" around each stud so the head technically can move around. However, given all the studs and the machining accuracies involved, the head tends to "center" on an average - and this average is where the bushing is centered to. And hopefully centered above your broken stud.

I would expect the drill size to be the 50% size above. It takes four threads to develop full strength in a bolted connection, and given there is typically 11 threads on a head stud into the block, you can give up a little bit of "root" to one side or the other and still develop full strength.

I would not rush into driving a 7/16-14 tap into that drilled hole. It is very easy to "cross thread" where the thread you're cutting is cast iron - which is quite soft compared to the remaining bolt thread.

Rather, I would "pick out" as much of the steel spiral as you can to try to establish a "line" for the tap to cut into, and use that.

Another modus I might try would be to use the kit - but instead get a LEFT HANDED drill of the proper size which, by the heat and torque of drilling, might back out the stud without further ado, once a good portion of the hole is made. I like that thought the best although left handed drills can be pricey. https://www.amazon.com/Left-Hand-Hea.../dp/B002FCK65U

Hope this helps, been there done that.

Joe K

Re: Continuation from stuck engine thread< Now what>
 

Definitely lottery ticket time

Re: Continuation from stuck engine thread< Now what>
 

Replace all your studs and nuts and put it back together. The stud broke not the threads.

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Agreed, I ordered a new set of grade 8's

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Just a suggestion........ The suspect thread hole with the broken stud that you "Lottery Carded out" ..... I would suggest taking one of the old studs that you remove and do your best to hack saw a groove across the threads and then double nut the top and lock them together and oil up that hole and kind of use the "used stud as kind of a thread cleaner to clean out any debris or built up rust in that hole. It can't hurt and only help in the future! Turn it in and out a few times.

Re: Continuation from stuck engine thread< Now what>
 

I chased the threads with a tap and some light oil. I then took a short bolt and tightened in the hold to check the integrity of the threads. All seems good. The real test will be when the new head studs come and I install everything again. Today was spent switching the car back to six volt. I do truly appreciate every ones input, Thank you.

Re: Continuation from stuck engine thread< Now what>
 

You can pull test the stud holes with the head off,just use a 7/16th NC bolt and stack a few greased washers(make sure you get grip length but dont bottom the bolt) and gently pull torque to 55..or 60 if you want,better to find out with the head off if you need to helicoil a hole.

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So glad you were able to get that broken stud out somewhat painlessly. Also glad to hear that you heard the warning and are replacing them all. I pray that will go easily also. Chap

Re: Continuation from stuck engine thread< Now what>
 

Hello All.
So..... Does it run? How'd it all work out?
Thanks Howard.

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55 ftlbs on a fine thread will give much more pressure than the same torque on a coarse one. I'd have yo consult charts to see what the coarse thread would have to be torqued to to ge the same pressure but it will be too much. Use a proper stud.

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I would not test. I would put the new studs in and torque to the indicated amount. If one fails you fix that one.

Remarkable thing about bolting. More bolts (almost all) fail in torquing than fail in service.

VW brought this to a high art with their "stretch bolting" which are actually designed to be set above the yield point of the fastener. Same "failure test" applies.

Joe K

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Odd place to break. It must have been over stressed at one time. Ive never seen a stud break there.