Engine rebuild - look at my bearings

[mmasse]

I just finished splitting the case and cleaning the parts.

I would need some guidance to assess the damage.

The crank bearings don't look to be in good condition. I guess I would have to replace all the crank bearings, right?

Do I have to replace all the other bearings, as well? The intermediate shaft bearing look also a bit worn.

Please, also take a look at the 3rd picture. The section central section of the case looks to have some damage. What's the possible cause of this, and what should I do? I already cleaned it but it there is clearly some material damage there.

[gsholz]

re 3rd picture, looks like some minor fretting damage, i.e. the two parts moved against each other. I have seen this in aircraft engines (also horizontally opposed 6 cylinder piston engines). Maybe due to inadequate torque at last reassembly or surfaces were not machined true.

[mmasse]

Gsholz,

Will this require the case to be machined?

[lindy 911]

Bearing wear looks about par. The fretting doesn't look all that bad. I think I would knock down any raised spots with emory cloth and put it back together with new bearings. This is where the Locktite 574 comes into the equation as it will glue the tow halves together providing an extra bond to help prevent this in the future. Aren't you glad you split the case?

Make sure you test all the piston squirters too.

[mmasse]

Yes, I am!! How do you test the sqirters ? What holes do I need to plug to test them?

I had one issue which I will have to solve. One of the studs on the edge of thhe case broke and I will have to take it out somehow. I will post a pic later to seeof you have any recommendations. I hope I will be able to do it myself!!

[lindy 911]

Look on the piston side of the case and you will see the squirters. Make a block-off from a piece of 3/8" fuel line with a 6mm screw in the end to stiffen it up. Look down the through-bolt hole and locate the oil passage and block it with the fuel line. Apply air pressure to main bearing outlet in the same web until the squirter blows air. It might take a little coaxing. I used Seafoam in the ones that were stuck and it worked great. Once the are open and working put some motor oil in the hole where you apply compressed air. Blow oil through the squirter until it makes a uniform spray pattern.

[mmasse]

Thanks lindy911

now, what do I do about this broken stud. is there any way to take it out without damaging the case?

[lindy 911]

Yes, it can be drilled in the center and an extraction tool can be inserted and the stud screwed out. You may / should use heat.

[Walt Fricke]

It is hard to get a drill started right in the center of a broken stud. When the stud protrudes, you can grind the end flat, center punch it, and have a good chance of success. But this one is broken below the surface, so I was going to suggest taking it to a machine shop.

Then I looked at a case to be sure my memory was right, and you are in luck (of the it-could-be-worse sort). This stud's other end is flush with the other side of the case half, and has a nice flat end. Not like the cylinder head studs, which go into blind holes. So you should be able to center punch it and get a hole started pretty much right down the axis of the stud.

I'd start with a relatively small drill, and work up until you have removed quite a bit of the stud from the inside out. Then soak with PB Blaster or the like, and give it several heat cycles to try to break the corrosion which has locked the threads in place. Then try the screw remover.

Drilling from the backside may have another advantage. The rotation of regular drill bits is going to try to screw the broken stud bit out the other side. No need to get the reverse twist bits we use when trying to get studs out of blind holes. Though if you have access to those you could try it both ways.

[mmasse]

Thanks Walt,
I was actualy thinking about that possibility, but i was scare to no align the drill straight and end up screwingbthe case . I will give it a try with the smallest possible bit and see where I end on the other side of the bolt. It would be much easier if I had a bench drill, but I dont have one.

I will report back when done

Thanks

[boyt911sc]

Originally Posted by mmasse

Thanks Walt,
I was actualy thinking about that possibility, but i was scare to no align the drill straight and end up screwingbthe case . I will give it a try with the smallest possible bit and see where I end on the other side of the bolt. It would be much easier if I had a bench drill, but I dont have one.

I will report back when done

Thanks

Mario,

If you don't have a bench drill press to use, I would not recommend you doing it. Unless you are willing to take unnecessary risk. You could easily break a drill bit and make a bad situation worst but it is your call. Find some one (shop/individual) who could help you removed the broken stud. However, if you think you could do it and follow prudent course of action, go ahead and tackle it. Just my two-cents.

Tony

[docrodg]

FInd a local machine shop, offer them 20 bucks and a six-pack, and get it drilled out by them. The six-pack is so you can take a couple things there later for a quick "eyeball" or a good dunking in the cleaning tank

[bullethole]

Bearings are relatively cheap. while you have it apart, replace all of them.

[KTL]

That picture of bearing #1 is a good reason to split the case. Anybody who tracks their 911 car regularly, is likely to do some aggressive clutch operation. The reason the #1 bearing is different that the others is because it needs thrust support at that end. The shock loading of the clutch puts a lot of thrust load on the crank and in turn puts a hurtin' on that bearing.

The rest of the mains are indeed well worn. I suspect that engine has seen its fair share of high rpm usage. Agreed with Lindy; aren't you glad you split the case? Main bearing set isn't cheap, but it's better than failure down the road......

[Walt Fricke]

I wouldn't worry over much about trying to remove the broken stud. If you end up buggering up the threaded part, not to worry. After getting the broken part out you can bore the remaining hole out to 8mm, and just use a bolt. As Porsche does in the hole right next to this one. Or you can install a Helicoil - the tool and a handful of 8mm thread inserts are not expensive at your local high quality hardware store (or by remote purchase elsewhere - and the threads will be as good as new for their function.

I'd not want to use a really small diameter drill - too likely to break. Just use what looks about right. You may be surprised at how close you can get to a right angle with a hand held electric drill. And don't try cheap hardware store screw extractors - you will need a fairly small one, and those can break off. When that happens you have to go find a shop with EDM - electric discharge machining. This exotic gizmo literally burns out what is in the hole, and is so precise that when done all you have to do is pick the thread remnants out of the intact case threads. About the only thing which will deal with broken drill or other hard but brittle tool steels. Though this process of going from bad to worse usually happens when a guy is changing exhausts with engine in car. You have the case in hand, and it is easy enough to take elsewhere for work.

If no machine shop is convenient. Were this mine I'd try with the drill. I have a reasonably large drill press, but I'm not sure the table is large enough to deal with something as large as a case half, or with the porcupine effect of all those other studs.