broken cyl. head screw

[imported_ricardo]

i opened the port side cyl head with no problem but the starboard cyl head haded 2 screws that wouldnt come out, i tried very carefully to take them out but one of them broke ( starboard cyl head ,) the screw at the lower corner starboard, will i have to take it to a machine shop? or can i get it out with an estraction drill eaven that the screw is like frozen there? give it some heat ,wd40, or give it some carefull blows with a hamer so that the sediment that the screw has may loosen?:%

 

[Silvertip]

Re: broken cyl. head screw

If the end of the bolt is above the surface of the block, carefully grind it flat. Then center punch it. Using a small drill bit, drill into the bolt. Gradually increase the size of the bit until you can get an easy out (bolt extractor) into it. Don't even try a smaller size easy out as it will likely break. Increase the hole size until you are almost into the threads. Then use an easy out. It may help to insert some Tri-Flo other penetrating fluid and let it soak for a few days. Then try to extract the bolt.

 

[ezeke]

Re: broken cyl. head screw

If you have been able to remove the cylinder head and stubs remain, heat will probably loosen the bolts enough to remove them with vise-grips.

I've found most of the binding corrosion that caused the break was in the shank passing through the head, rather than the threaded part within the block.

The trick is to get the cylinder head off with the stubs in place.

 

[imported_ricardo]

Re: broken cyl. head screw

thank you guys!!!d

 

[F_R]

Re: broken cyl. head screw

Personally, I hate easy-outs. In the first place there is no such thing. They aren't easy and they don't get it out. If the bolt is so correoded in that it didn't have enough strength to get itself out, why would anyone think that a skinny easy-out would not break also? In addition, Easy-outs expand the shell of the broken screw and make it tighter than ever. And once you break the easy-out, you are dead. They are too hard to drill out.

The real cure is to drill out the screw and install a Heli-coil. Drilling out screws is a learned skill. You can really mess up if you haven't learned that skill. One thing to be especially aware of is ALL the old screw has to be out before you go running a tap into the hole, or you will break the tap and be dead again because they are too hard to drill also.

 

[DJ]

Re: broken cyl. head screw

One of my engines is a 30 year old Johnson 50 used exclusively in salt.

I broke many bolts :| removing the lower unit and cylinder head.

Fortunately, all of them broke off just under the head of the bolt. In each case, I heated the bolt (not the housing/block) and could twist them out, with good vice grips.

When you try to twist them out, DO NOT try to take them directly out. Go back and forth (tighten/loosen) and ease them out. You'll see all kinds of corrosion fall out of the threads.:^

 

[iwombat]

Re: broken cyl. head screw

DWJ, you beat me to it. Hopefully the fasteners in question broke off enough above the threads to get some vice grips on 'em.

Time for the blue wrench.

 

[imported_ricardo]

Re: broken cyl. head screw

my engine is a evin, 235 from the 79 almost thirty years and as long as i know that engine has never been opened aparently the owner before me did'nt used much

 

[imported_ricardo]

Re: broken cyl. head screw

fortunately broke under the head

 

[Scaaty]

Re: broken cyl. head screw

I'm with FR...EZ-outs have a place in certain applications (Machinist by trade here), and this AINT one of them.. You break one off, the block is coming off, its going to a machine shop the has an EDM machine, and it will have to get burnt out, and you had better have a full wallet. Heat and hope, or drill it out and stick a steel insert in

 

[ezeke]

Re: broken cyl. head screw

Just in case you ever do need to drill a broken bolt out, here is a link you may want to add to your favorites:

"http://www.mytoolstore.com/hanson/hanson.html"

Copy to your browser without the quotation marks.

 

[mikesea]

Re: broken cyl. head screw

You say fortunatly broke under head.So I ASSume you can get vicegrips on the bolt.You can use heat ,I like to spend the xtra money and buy mapp gas using a tip that can be ignited by pressing the trigger.When bolts are broke below the surface,I find it siccessful to make the last hole drilled like others mentioned,but use a left hand drill bit.Of course you need a drill that runs reverse too. This bit will usually remove the old bolt fragments by kinda snapping them away from the threads.Using heat and a lubricant increases the chances/.I have never had a problem removing bolts that vicegrips will cleanly snap onto using heat,patience. Start by lightly moveni the bolt back and forth grabbing a bit more each time. Patience is a virtue.

 

[R.Johnson]

Re: broken cyl. head screw

One method I have used with good success is to install the head just using two, or three bolt's to get it in alignment, then making up a drill bushing that is a push fit in the cylinder head bolt hole, though I have a lathe which makes this possible. That makes the drilled hole right down the center of the broken bolt. Another tip when drilling these stainless steel bolt's, use a good quality sharp drill. If the drill stop's cutting, and spin's in the drilled hole, it will spot, or work harden the bolt, making it very difficult to start drilling again. Using a cutting fluid with the drill is also a good idea. With a lathe, these bushing's are very easy, and quick to make. You can make them out of anything, as they need not be hardened for just one time use. As FR said, don't even think about an easy-out, you snap one of those off, and you have really slamed the door.

 

[kenmyfam]

Re: broken cyl. head screw

Left hand drill will often help to loosen things up just by drilling. The drill bushing suggestion is a very good one. Easy outs do have a place in the bolt and stud removal environment with limited access. The best easy outs are the ones you can get a socket on and not just a wrench.
My favorite is to use the drill bushing as a guide with a left hand drill, then tap a left hand thread into it, then use a left hand thread bolt into it. Make sure the bolt you use is of premium quality and most times as you tighten the left hand thread into the broken stud or bolt it will bring out the broken stud with it. Having said that, when it does start to move go gently both ways with it and gradually increase how much you rotate it till it is loose enough to draw all the way out. You can put a lock nut on the bolt as well if you need to.
Good Luck.