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Replaced head gasket on my 21hp Briggs. Everything was going fine until the headbolt at the eight o’clock position snapped at the thread level. I’ve managed to drill an off center hole but the Easy Out isn’t doing its job. Any suggestions? Can I put an insert in the block?
Thanks
John

Hi John,

I haven't had much success with easy outs.

You could try heating the area with a propane torch to see if the easy out will extract the broken bolt.

Only other option, would be to take it to a machine shop to see if they could remove it and place a helli coil in the block or try drilling and tapping to the next larger size.

There are YouTUbe video's showing guys welding a nut to the broken bolt and extracting it that way, if you want to try.

Regards

Jeff

I'm with JP, take it to a local machine shop and have them do it.

Do a search for "Stud removal" or "bolt removal".
There are special electro spark erosion machines designed specifically for this purpose.
There are water plasma machines designed to do this as well.
Oz is a tiny market and we have a dozen workshops who do nothing but this and for me a mobile workshop that comes to me & does the work in situ.
Not cheap @ $90 (AUD) but worth every penny.
I had one bloke who did a bolt at the back of one of the rollers in a position I could barely get a flat wrench into.
Usally all that is needed when they are done is to run a tap through the hole to clean the thread.
In the land of oppertunity & enterprise there must be people doing the same thing.

The broken head bolt is circled in yellow at about the 7 o’clock position. I’ve drilled a very off center hole in the bolt and easy outs aren’t working. On the top side at about 11o’clock position is a locating pin. The distance between the head bolts is 3 1/4 inches and it is about the same on the bottom side if you consider the broken head bolt as a locator pin. Is the broken head bolt critical to the integrity of the engine? I’m thinking this thing might runs quite well if I just put it back together. I’m sure smarter guys than have an answer. I’m just using the machine as a lawn tractor and have removed the mower deck.
Thanks,
John

I dont think it would interfere with structural integrity of the engine, but you *might* blow head gaskets in that are due to there being no torque, or not get a good seal.

As it is there are not enough head bolts on these engines which regularly blow head gaskets as it is.
There is no way the clamping force will be consistent enough for the engine to work without leaking for more than a 1/2 dozen thermal cycles.
So if you want to et a lot of practice replacing head gaskets put it back together the way it is.

If you don't want to take it out then get a Dremel tool or equivalent and a pack of carbide cutters.
To et that deep you will probably need a flexiable shaft drive as well.
Put on some Nitrile work gloves to prevent you hands from very sharp metal splinters and cut the bolt out or at least cut the hole back to centre then drill it out.
When you have a pilot hole that is centred then drill the thread out in one hit .
people make the mistake of stepping up the hole one drill size at a time which will guarantee you run off centre and wreck the cutting edges of your drill bits to boot.

Worst case is you will either have to helicoil the hole or tap it next size bigger.

I finally got the broken stud out but there wasn’t enough material left in the case to chase up the old threads. I noticed that the headbolts actually terminates outside of the cylinder finns so I drilled the threads out and used a long grade 8 bolt and nut on it. So far, so good. A much better alternative than scrapping the engine. John

bertsmobile1 said:

When you have a pilot hole that is centred then drill the thread out in one hit .
people make the mistake of stepping up the hole one drill size at a time which will guarantee you run off centre and wreck the cutting edges of your drill bits to boot.

Click to expand...

I actually have right the opposite result on keeping the bit center and I don't worry about the bit getting dull as I have a bit sharper if needed. Now of course I free hand the drilling too. ONe thing about bits is that you got to have good quality bits; those big box store bits are lousy for me to use. Some can't drill the first hole without dulling.

Well........ twist drills......drilling out broken head bolts. After a lot of weeping wailing and gnashing of teeth i do it this way. I made a steel jig about an inch tall with a holes that fit 1/8" drill, 1/4" drill and a center punch. I use other head bolts to clamp the jig down so to stay straight. I have some good drills but the Hazard Frought cobalt ones and a drill Dr do just fine. I can usually get the broken piece out and save the threads.

Yes having a centering jig works best which would be great if I work on the same bolt pattern but I don't. Or if I did multiple engines with the same bolt pattern but again it more like one here and one there problem. If the screw is simply broken off from over torquing then a good left hand drill bit spins them out. It is those that are fused (galled) in place from excessive heat that are the hardest for me to get out and there is no easy way to save the threads either as that is what that is fused. I have seen screws so heat harden that only a carbide bit can cut them out especially when an extractor breaks off. Which I have quit trying to used as I broken several trying to remove screws; hence, that when the carbide bits comes out of the tool box as they are the only bit I know that cut those extractor bits.

Lately it has been the Kohler valve cover screws that are a pain which I just drill out the M6 screw and retap to M7 as there is enough metal to work with. It is not just head screws either as I have done exhaust studs and screws too.

I supposed I could take 1/2 a day making an one time use jig on the drill press but most likely I lose it before the next job a few years later. Also for the head jig it would be a lot easier if I had a spare to use while making the jig but normally I don't have a spare just laying either.

Just wait until you break off a tap as they shatter. I have tried those broken tap extractors but my luck they all broke instead removing the broken tap. I now know the secret of keeping a tap from binding in aluminum and it is not using cutting oil as that is just a bad as trying to tap dry.

I do however do a few jigs that I designed for mower work. I just design one for double D electric clutch retainers that is recessed. Just got to see if the aluminum holds or if got to make in steel. I am hoping that 65 ft-lbs don't destroy the aluminum version as a 2" steel blank is more expensive and a lot harder to mill.

My jig is not bolt pattern dependent. It is a piece 1 inch square about 6 inches long with the holes in one end. I just lay it across the head with the hole i need centered over the broken bolt and i use another piece of metal across it and use two head bolts with it as a clamp. My farher was a millwright and taught me how to use a tap and die. I still have some taps he used when he was in the WPA. As he said " you gotta have the feel for it".
Of course there is the old trick to bolt the head on and use the bolt hole as a guide.

JAG43 said:

I finally got the broken stud out but there wasn’t enough material left in the case to chase up the old threads. I noticed that the headbolts actually terminates outside of the cylinder finns so I drilled the threads out and used a long grade 8 bolt and nut on it. So far, so good. A much better alternative than scrapping the engine. John

Click to expand...

This would be a good one for this thread. "Happiness is."