stud removal on a 9n, need some advice

YMMV,

TOH

This is an engineering fact.

Zane

Sort of. I don't know about twice the force on that particular diameter and pitchs but yes the nut will produce more tension in the fastener at the same torque. However that misses the original assertion that the strength of the connection is stronger - it is not. The weakest point in the system is still the threads in the block where the stud engages. The block end threads on the stud will fail at exactly the same tension as they will with the bolt (assuming like materials). That too is an engineering fact.

The relationship of torque, thread pitch and tension is why the recommended torque values for the bolts are HIGHER. The higher torque results in the SAME tension in the bolt as you get at the lesser number for the stud. Two different torque values but the same clamping force and the same load on the threads in the block.

The strength of a threaded connection is simply a factor of how much cross sectional area is engaged by the threads and the tensile strength of the material. Because the Unified thread profile is 60 degrees and the root depth of the thread diminishes with finer pitches you get less area engaged per thread with fine threads but more threads engageed for the same length of engagement. The percentage by which the area dimenishes is less than the percentage by which the number of threads engaged increases - hence finer threads for any given diameter have a greater cross sectional area engaged and are stronger.

A simple synopsis of the engineering formulae involved may be found in Machinery's Handbook. A full and definitive analysis may be found in Federal Standard H28, first published by NBS shortly after WWII and revised a few times since to accomodate more recent thread forms. Frankly i prefer the Machinery's Handbook. My eyes glazed over within 5 minutes of opening H28.

Regards,

TOH

On hot cast iron block?!?!

I wouldn't try that one on my block.

The only time I had a stud like that to remove, I tried until I almost broke it, then I used penetrating oil. Following the instructions, I'd squirt a little oil around the base of the stud, then take a hammer (not a big one) and start tapping on the head of the stud. Something like 20 taps, then stop and put some more oil. Tap, oil. Tap, oil. After about 10 cycles, I was able to unscrew the stud with relative ease. I used vise-grips, and worked it back and forth a few times, then out she came.

I've seen the method described below, where a nut was welded to the end of a broken stud, touted several times on the Model T website. Apparently the heat from the welding does a similar job to the oil-tap method.

Just my $.02

Dan

The right tool for the job makes a huge difference.

Dan

You are right to be leary about breaking off the studs. Most of them are into the water jacket area, so they have water or antifreeze coming up into the threads causing corrosion and weakening of the stud.

My approach would be to direct the torch flame on the stud, but not on the block. I know that this seems to be counter intuitive, as the stud expands and gets tighter in the block...but begins to break loose the corrosion bond. Then let it cool and shoot your favorite penetrating oil on it while cooling. The pen oil should work its way into the thread. Heat and cool a few more times for good luck. You are doing 3 things all at once...1) driving the pen oil deeper each time, 2) breaking more of the corrosion bond with each heat/cool cycle, and 3) each time the stud goes from red hot to cold it shrinks to a bit smaller size than it started as. Then I usually double nut it, locking the 2 nuts tight together, and then putting some forward and back wrench motion on the nuts to loosen the stud. If you have any sense that you are about to break the stud, just go back to the heat/cool & oil routine for a few more cycles. Once you get it to move, do not unscrew it in a continuous manner as it usually gets tight again, but rather unscrew it a bit, and reverse to tighten it a bit, and then unscrew it a bit further with more pen oil. Your time and patience will be rewarded by not having to drill out a broken stud.

Best of luck!!

Paul in MN

If you have to remove them, the stud removers I have seen provide a way to clamp on and make it easier to unscrew them without getting off-center and snapping them. Should work on any engine but that is one of the few tools I have not needed to get. If you do remove them, replace with new studs and make sure you get the correct length in each hole for the head you are using.

The last really rotten set I had to remove came out with a pair of vise grips and a couple whacks with a hammer. Except for one, of course. That snapped off about a quarter inch above the head. I slipped a slightly oversize nut on what was left, covered the area with some thin sheetmetal for protection, and welded the nut to the broken stud. Then, it came right out with my impact wrench. Heat from the welding probably helped alot. Be careful with heat around the deck surface cause you might warp something.

A few studs usually come out when you try to remove the nut. They should be replaced with new ones (but I have been known to reuse them if they look ok). At least that eliminates the usual snafu of getting the wrong length studs. Remember to put some sealant on them to seal the water jacket.

The most important things to do to prevent problems with the head is to make sure both the block and head are flat, use a good quality head gasket, follow the correct pattern when you tighten the bolts, don't overtorque them, DO go back and retorque them after the engine has gone through a heat cycle. People who have had problems will eventually admit to skipping one of these steps.

I would take the torch and turn the studs red, while tryin not to heat the block anymore than I could help, then get a holt on it with vice grips and work it, and remove it.