The xzn heads are pretty undeep and if you don't get the bit in all the way and true, they strip easily. Itnis wise to insert the bit, then tap on it a bit to make sure it sits really well, then put the wrench on it. Or put it on the wrench first, insert it and tap on the wrench a bot, whatever is more comfortable. Btw bit quality also matters. For this tricky and sensitive job I only use a Gedore bit.

 

The best way to get the xzn bolts undone is to use a manual impact driver (the type you hit with a hammer to rotate). That ensures good purchase into the head of the bolt, and greatly reduces the chance of stripping.

There isn't quite space to get one into all the cam cap bolts however - so for the other few, a nerve-wracking time with a breaker bar, a quality undamaged bit, and a few taps with a brass hammer on the bolt before trying is the way to go.

Or, just pull the engine - seriously, its not that big a job and makes access to all the other bits like the end caps much easier/faster, and then you can get at all the fasteners easily, as well as MM's etc.

 

Just curious but what is the name of the part that is held by the stripped bolt I was talking about? Just curious what a used is worth? I could not locate the part on 928 international

 

Cam bearing cap IIRC. Basically, it's worth the price of the whole head. It's machined to match the opposite bearing surface on the head. Every cap is different and goes exactly back in the same spot and same orientation.

I have had to grind off these before. I recommend the flexible snake extension for the Dremel with the smallest grinder bit. Be very patient. Go slowly. The bearing cap can tolerate cosmetic damage but you don't want to take a hunk of 'meat' out of it with a gorilla-size tool.

 

[Edit: What Dave said ^^^ ]

I think it is called a cam cap, and you DO NOT want to screw it up. They are matched to each position and line-bored with the head, with no separate part#.

I had to drill three of those silly bolts (out of four cams), in spite of good toolbit, lined up true, tapping in place, etc. etc. So your one-for-four is no worse than I did. Sometimes they just don't want to let go.

I degreased the area around the bolt-head, draped everything with rags, then covered the engine (whole front of the car actually) with thin painter's plastic sheeting. I cut a 1-2" hole where the bolt was and then used tape to seal the plastic to the cam-cap, leaving only the bolt-head exposed. Sort of like surgical drapes, everything covered and sealed except the tiny bit that you are going to perform mayhem upon.

Then I drilled into the bolt-head with a 8mm bit (the diameter of the bolt shank), using a close-quarter drill (older version) and a short 8mm bit. You can't hurt the cam cap (if you drill straight) because the drill is smaller than the thru-hole. When you get close to drilling-thru it may loosen with vice-grips as the pressure gets relieved.

Be sure that you have the oil drains blocked with rags (five I think), you do not want to chase anything down there.

 

I might first try to use one of the easy out drill bits. I can't tell you how many times i had wished for a drill like you proposed. Has anyone used this drill? Harbor has a 25 percent off one item today.

http://www.harborfreight.com/3-8-eig...uck-95877.html

I like the surgical idea, with the plastic sheet. Where is the drain blocks, i know its been brought up a few times.

Cam cap, i figured the part number of the covers would allow for replacement. I am replacing the camshaft from another car.

Great the added stress of a $5 bolt to possibly $500 plus....wow wee

In regards the snake for the dremel. What benefit does the snake provide you? My dremel is pretty darn old and looks nothing like the new units of today. Its red in color and a lot smaller. Its possibly mine is a hobbyist dremel

 

Phil, the oil drains are under the exhaust cam, literally at the lowest point of the head. Their job is to return oil (and any dropped small parts) to the sump. They are rectangular openings about 1/2" wide-- peek around under the lower cam with a flashlight and you will find them.

If you have a Dremel then that will work, it will just take longer. The problem with flying debris is the same or worse, so cover and tape everything carefully. The flexi shaft (snake) just makes it easier to do delicate work, because you are not supporting the weight of the motor while maneuvering the tool. With a small Dremel I personally would not bother. And the nice thing about Dremels is that they don't cut that fast, which means they can't create mayhem very fast either. As mentioned, the important parts of the caps-- the mating surface to the head and the bearing surface-- are all protected until you get it loose. The biggest concern is keeping things clean.

Cheers, Jim

 

Let me know if you need help... I can slide by tonight or possibly tomorrow around lunch time. I have a 90 degree elbow for a dremel you can borrow if needed.

Once you drill, grind, cut the bold head off... the remaining threads will be easy with vise-grips with the cap is out of the way. Like Jim said, the most important thing to do is prepare a 'shield' to keep any debris out of the engine.

Essentially you'll be doing something like this:


Obviously, a drill would be a better (less time consuming) choice. If you can't get a straight shot at it, you'll need a close quarter drill.

 

I am working tonight Kurt but thanks for the offer. I hope to start the surgery on thursday or friday. I don't own a special drill as of yet but this might be a good time to buy one. I'm afraid once the bolt head is cut off the other portion of the screw won't unscrew out. It was mentioned the tension would be gone and the remaning part will come out. I guess I am just a worry wart. I am the least experienced with striped screws.

 

Phil,

I assume you saw Don's post on the oil drains? Good pic's. Of course if you plug the drains you don't need the camera

Here: https://rennlist.com/forums/928-foru...s-the-day.html

and here: https://rennlist.com/forums/928-foru...ml#post9759787

 

What kind of tool and wrench are you using to undo the star head bolts?

 

The picture below shows the point and which the cam bearing cap is about to 'pop' loose.

As you can see there's two layers of 'protection' around the work area. And as I previously mentioned, I use the Dremel and the flexible snake attachment with two sizes of bit. I use a medium-sized grinding bit to get the 'meat' off and then the smallest bit for the detail work.

I use the snake attachment because it allows me to get at the bolt head from a lot of different angles and it allows me to use the grinder bit with the (near-)precision of a dentist. You can hold it close to the tip and get a lot of control. It will be harder to be precise with the mass of the Dremel fighting your fingers.

While I'm grinding the bolt head with two fingers of one hand, I use the other hand to hold the business end of my shop vac to suck up the debris. That's why the work area shown is almost spotless.

 

Root canal!!!! nice work.

 

I had the same problem when I was disassembling my engine. I used the bolt extractors to break the stripped bolts loose:

http://shop.advanceautoparts.com/buy...ing-tools.html

 

I need to get me a set of those just in case. Too cool!