Dilivar Disappointment Inside - shopping parts list?
 

Found this yesterday on my 2.7L after it knocked the plug wire off in 2nd gear:

http://i458.photobucket.com/albums/q...-05-08_656.jpg

I've done a few engine assemblies/disassemblies/engine conversions etc in my watercooled VW life but I'm new to these cars and engines. By new I mean I'm within the first week of ownership...so this is my baptism by fire if you will. The engine has already been through the major overhaul including case split, full work-up within the last 50k miles and the pedigree was communicated as RS pistons/heads with dilivar studs. I'm ready to jump into this job tonight and to see it through to completion. I have a plethora of tools and a well lit modern garage to clutter up with engine removal.

My question to you, the seasoned head stud replacers, are the basic requirements to complete the job. I have these parts in my cart here and I'm staring cross eyed at my credit card:

1) 1974-77 Complete engine gasket kit: 10-0904-106-M17
2) Supertec Headstud kit: SPTC-HSK-1
3) 90MM Piston ring set, quantity 6: 911-103-939-00-M42
4) Piston Ring Compressor Set (TOL-KD850)... narrow enough to install piston through bottom of the jug so no rod removal required.

Am I missing anything else? The engine job is fresh enough in the car (chain tensionsers, alternator done 500 miles back for example) that the majority of the fasteners are fresh. I would prefer to limit time waiting for parts to come by mail if possible.

Thanks for the click and responses.

http://i458.photobucket.com/albums/q...-19-30_507.jpg

Someone else posted this list when my engine broke a stud:

Head studs X 12 $144
crankcase gasket Kit $57.75
Cylinder Head Gasket Kit $215
Cylinder to case gasket (.25mm) $36
574 Locktite case sealant $22.75
chain ramp brown $6.5
chain ramp black X5 $32.5
solid oil tube lines X 6 $53
Piston ring set $142.5

You may not need new oil return tubes or chain ramps since the engine was done 50k ago, but I'd replace them while I'm in there. They're cheap enough and you might as well.

Thanks for the post and suggestions.
I believe the list you provided matches mine with the exception of the tubes and chain ramps. The chains/tensioners were just done about 800 miles ago (I forgot about the miles I drove since purchase). The tubes were replaced during the last overhaul and look perfect from the bottom. I will proceed cautiously with my dis-assembly in order to determine if any of these basicaly new parts need replacement. I will hold my parts order until I determine the extent of repairs as I understand the magnesium case is prone to studs pulling out requiring more extensive repair.

Supertec head studs.
Anything else is just silly...............

After reading through the search results I was hoping you would weigh in here Henry. I do plan Supertec when the time comes to place the order. As stated originally - I'm not new to engine work but I am new to Porsche/air cooled.

This may seem like a silly question... what engines came with nikasil coating? Is there any coating on a 74 or should I be okay to ball hone this when the new rings go in?

Thanks again for the input,

You mention a 2.7. First thing to do is pull the valve cover and see if the stud is broken or has pulled from the mag case. I doubt it has unscrewed itself.

If the stud is broken (yes a possibility with dilivar) then you can replace studs. However, the epoxy coating on those studs looks like it is in decent shape and one does not usually expect dilivar on the top row unless they have all been replaced. It is common to use dilivar on all 24 studs with a mag case due to expansion rates of the two metals.

If the stud is intact, it is possible that it has pulled the threads from the Magnesium case. If this is what has happened then you will need to tear it completely down to machine inserts and possibly linebore.

What is the history on the engine? You mention it is new to you, do you have records?

I do have records that I left at a relatives home last week after I picked the car up. I should have them in my mitts again this weekend. The engine work is thoroughly documented in the records including photos of the work... by my measure of opinion it was properly done. The statement of purpose for the previous overhaul was for replacing the valve guides as well as performance enhancements of fitting the Porsche Mail Order 40mm Webers, RS Pistons, Heads, turbo valve covers, remote oil cooler, centrifugal advance distributor and etc.

I will remove the valve cover over the lunch hour (at home office) to gain access to the stud and report back.

In that case, you're probably fine with the ramps and return tubes unless one breaks on disassembly.

Have you been able to get the offending stud out of the engine? You should be able to see if it pulled or broke at that point. If it pulled, your costs are obviously going to go up significantly. Line bores are pretty much standard on a 2.7 when you open the case.

On a 2.7 in the picture, thats a loose dilivar so the inserts have probably been done but someone failed to loctite the stud.
Bruce

I was holding my breath while fishing this out as I had pushed it back down the hole to get the plug wire back on. I guess I got lucky.

http://i458.photobucket.com/albums/q...-03-54_757.jpg

I have a good picture to upload from my slr later tonight of this stud. You can see in the cell phone picture above what I'm going to point out in the SLR picture that shows it much more clearly. The body of the stud has striations in the same manner as the cardboard core of a roll of paper towels or tp...to me this is an obvious indicator of a tooling flaw during the manufacturing process as they roll out the stock. These striations are the same angle as the break. The tool must have had a bur that was imprinted on the body of the stud top to bottom circling around about 1cm at about 30 degrees... definitely a sign of piss-poor quality control.

Keep in mind when ordering a gasket set that the Victor Reinz gasket sets are far inferior to the products offers by Wrightwood Racing.
The quality of the Victor Reinz have been deteriorating over the last few years to a point where we won't use any of their products.

Yup, a stress riser will do that. They'll all break eventually.

Good news though. When you get the engine apart, be sure to check all the studs for signs of them pulling out of the case. There's never any guarantee that they weren't in the process of pulling when the stud broke.

It seems you could save some money and use a generic piston ring compressor you probably already have like you would use to install pistons from the top of a water cooled engine block.

With the 911 cylinder on a bench install the piston from the top with one of those and push it down to the bottom so the piston skirt and wristpin hole is sticking out. Then slide it on the studs part way and install the wristpin and rod into the piston.

I havn't tried it but it seems that would work starting with #3 and #6 cylinders first on each side. Install the wristpin circlip closest to the flywheel end of the motor before installing the pistons or it may be difficult to get at them on the other cylinders after 3 and 6 are installed in place.

the absolute cheapest way to go is just replacing that broken stud, $25.50 parts from our host, free labor. the other end has no fixed price. looks like enough of the stud is left to get a grip on it with just removing the intake. Should you just do that? up to you. I would replace all studs and have piece of mind. If you do one at a time, no need to remove cylinders as the engine was just rebuilt. r&r engine is required. Great looking car BTW

Thanks James - I'm in for replacing all studs as a one-timer r&r to get them all out with the belief that it will save sanity, time and probably cash in the long run. I will probably purchase rings from the host but I think I may steer from the Victor Reinz gasket kits. The valve cover gaskets in the images of the kit appear to be fiber which isn't acceptable.

Looking at the failure it looks as if the angle of the brittle fracture is about 58 degrees to the tensile axis of the stud.

Coincidentally this is about the correct angle for the Critical Resolved Shear Stress of a Face Centred Cubic material - (Austenitic steels such as Dilavar).

That's not to say that a surface defect didn't initiate the failure but the crack would then be likely to propogate at this angle.

When Dilavar studs fail with a flat fracture perpendicular the the tensile axis of the stud the failure is likely to be caused by a different mechanism.

Go with the Wrightwood gaskets. I got mine from Henry at Supertec along with his sealant kit. Aside from a minor issue of getting the wrong head gaskets in the set, it worked great.

And hey, misery loves company. Here was mine:
https://lh6.googleusercontent.com/-D...6/P1090055.jpg

The similarities are uncanny... if this were occuring on a modern car there would be a class action suit.

Started tearing down... figure I'll post the pics as I go here. Any help identifying the mods/parts here would be appreciated as I acknowledge my newb status.

Pics from this afternoon... plan is to drop engine on an evening after work this week, order parts for delivery before Friday and and to attack for re-assembly 1 week from today. Fairly aggressive timeline so probably more like 3 weeks to restart realistically.

Pic of the stud from cyl5
http://i458.photobucket.com/albums/q...1/IMG_3000.jpg

SSI Exchangers removed, needing a clean up from the oil leaker above
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Wiring for carb swap
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View from the bottom after an hour or so of cleaning/wiping
http://i458.photobucket.com/albums/q...1/IMG_3004.jpg

Exhaust ports measure about 34-35mm
http://i458.photobucket.com/albums/q...1/IMG_3005.jpg

Turbo valve covers?
http://i458.photobucket.com/albums/q...1/IMG_3007.jpg

The SSI exchangers weren't described in the sale. Seller stated simply "This car has everything that Bruce Anderson describes in his book for modifications"... :)

Funny enough, the stud that broke on mine was also on cylinder 5. 82 SC though, not a 2.7.

My guess: The middle cylinders will be hottest sandwiched between the other two... more heat=more thermal expansion and stress on the fastener. The cams on these engines must have bearing wear like crazy with this design.

If it were just a matter of heat, I'd expect cyl 2 to be the one that cracks the most as it's also near the cat. Although, perhaps the passenger side bank cools down faster and thus gets heat cycled more quickly. Who knows. Either way, at least one of the lower studs will eventually break.

If the studs are Dilavar then the increase in stress caused by expansion will be small and unlikley to be the cause of failure.

The stress in a Dilavar stud is about 45ksi even when peak cylinder pressure is taken into account.

The standard steel studs and the Martensitic Stainless Steel studs will develop higher stresses - which is due to differences in expansion- but only to around 75ksi.

None of these stresses are likely to cause stud failure unless macroscopic defects are present and the failures don't indicate this type of problem.

It is much more likely that failure is due to Stress Corrosion Cracking and precipitation hardening Austenitic Stainless Steels such as Dilavar can be prone to this mechanism, particulalry in the presence of Chlorides, when strengthened to levels greater than 160ksi.

The addition of high levels of Molybdenum used in Dilavar should be helpful in eliminating this problem but avoiding certain temperature ranges in the heat treatment schedule is likely to be more important, and perhaps not well controlled.

I am aware that this expanation is not widely accepted but the levels of stress developed in head studs is just too low without an additional failure mechanism being present. :)

It's likely a combination of things like you say... you do have to wonder on a stud such as mine that has the epoxy coating intact how large the role of corrosion played. All available literature describes the primary purpose of the epoxy to be for thermal insulation yet it also creates a seal that would prevent contaminants or corrosives from being introduced to the surface of the stud unless physically compromised such as a sloppy assembly ... which even then would be unlikely as the coating is quite durable. The embrittlement and/or risers must have occurred during the manufacturing... I do think the flat 6 air cooled design is partially at cause here due to the incredibly high, relative frequency of fastener failure. Either that or a manufacturer pumped out a huge run of compromised fasteners and a few different labelers continued to push them out after knowing (or not) the goods were tainted. I'd like to believe retailers would pull such product from the market place but who's to say inventory is thoroughly managed after it has been through a few wholesalers... they might not even know their stock delivered last week is 20yrs old.

I would agree that if the coating is intact then SCC does seem unlikely but to create tensile failures of the type being shown would need stress concentration factors in the region of 3-4 and the small surface defects that seem to present under the coating wouldn't generate this level of stress concentration.

Alloys that are similar to Dilavar seem to have a tensile elongation that is typically between 15and 20%. This would indicate that the material is relatively tough and reasonably notch insensitive.

Looking at the failures this doesn't seem to be the case and it is clear that the material is quite notch sensitive. This seems to hint that the material may have been poorly heat treated and that it is more brittle than it should be for this application.

The operating temperatures involved in the 911 engine is unlikley to affect the material properties of the stud and it is unlikely that the ductility has changed with time and the next time I have a spare stud I will carry out a simple tensile test and see what happens.

Gee that list looks familiar... :)

Taking my time breaking this thing down in the evenings after work... nice break from the desk after a more than full day. Popped the carbs off tonight as well as the alternator and some of the vents to make it a bit easier to slide from beneath later. Fresh alternator:


http://i458.photobucket.com/albums/q...ps85a148ba.jpg

Removing the alternator/fan allowed me to take a look at the top of the engine where I could see some of the cylinder gaskets pooped out between the jug and the case on 2 of the cyls:

http://i458.photobucket.com/albums/q...ps5d5ac2f2.jpg

http://i458.photobucket.com/albums/q...psefcde0de.jpg

Appears the case was outfitted with Time-serts (timecerts?) already.

http://i458.photobucket.com/albums/q...pseb79db81.jpg

Popped the starter out as well and then called it a night. I need to read up on the clutch release bearing activity that awaits me before I can drop the engine.

Yeah, I wonder where I got it from :)

The leaks at the head cylinder gaskets to the case are not a good sign of a quality rebuild. I hope you've caught it just in time.
You could damage the machining and never get a good seal again if left too long bouncing around on loose or broken head studs.
Hopefully the last rebuilder didn't ignore old damage. It can be machined again if it's not extreme. Just a light trimming using up some more $ for your credit card! :)

Do some serious cleaning and measuring. Find any other broken studs?

I did not see any more broken yet but I imagine they're in there. I can't view the bottom studs with the oil return tubes and air deflectors in the way. I do have an accomplished engine building machine shop close to the family so probably won't have to call visa for a limit increase. ;-)

In regard to the base gaskets failing - what is usually the cause here? Crankcase pressure or vibration? It seems odd they would come out like that as they aren't under cylinder pressure like the cylinder head gasket up top is. I wonder if they were damaged during installation or re-used during the previous build. Any insight on common causes here?

Lunch-hour progress today... removed the lower intake manifold/carb bases and then the main shroud so I could take a good look at the remaining top studs. All look fine. May drop tonight or tomorrow.


http://i458.photobucket.com/albums/q...ps0c9856a2.jpg

http://i458.photobucket.com/albums/q...ps3932954d.jpg

All free... just need to coordinate some higher altitude jack stands to get it out the back without messing with the bumper/rear pan. S

http://i458.photobucket.com/albums/q...ps025bd0c0.jpg

http://i458.photobucket.com/albums/q...pse0093fc6.jpg

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http://i458.photobucket.com/albums/q...ps58468d6f.jpg

Popped the rear bumper off and wheeled the engine out. Started cleaning up the grime/debris so it's cleaner once I do have it opened up.

Boxes of parts for the gaskets kit, 930 engine mounts/hardware etc arrived from our host very well packaged. I shared the Jellie Bellie treats which helped smooth things over with the lady that I was buying yet more car parts.

The studs run through inside the cylinders so you couldnt see a broken stud except removing the lower valve cover.
Bruce

I searched for awhile to try to find instructions on how to do this and the manual I have doesn't specify exactly how to.

How to remove the rear bumper on a 1974 Porsche 911:

1) Unplug license plate lights so wires are loose... this takes about 2mins with a flathead screw driver.
2) 2x8MM bolts on the accordion bumper trims on each side are accessible from underneath/behind. Take the two on each side that are furthest to the back so the accordions stay on the car and not on the bumper. After you get the nuts off the back you must push the accordion away from the bumper so the studs release.
3) Remove small caps on the thin rubber trim on the back bumper... one on each side. Don't take the big one off... leave it alone. They will be about 6MM wide and blend in... there are phillips head screws underneath that have to be removed as well. Once the screws are backed out, peel the rubber strips carefully away from the bumper only until you see two nuts on each side... these do not come off entirely in this step. Clean up before reinstalling so you don't have damage to the paint from sand etc.
4) 2x13MM bolts on each side are the last step for the bumper to come free. Be careful to support the weight of the bumper as you get to the last so you don't drop it and wreck the paint.

Installation is the reverse of removal.

I haven't made as much progress as I would like to this point but I think it's more important to get everything clean and to be thorough in documenting as you break it all down. I've been through a roll of blue shop towels, 50 nitrile gloves, and 3 cans of cleaner to get to the point you see below. The amount of filth that has come off the engine thus far is incredible and there is a lot more to go. There was grime packed in everywhere...

http://i458.photobucket.com/albums/q...1/IMG_3018.jpg

http://i458.photobucket.com/albums/q...1/IMG_3022.jpg

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http://i458.photobucket.com/albums/q...1/IMG_3026.jpg

My parts order from Pelican is in and the new headstuds are set to arrive on 10/3/2012. I removed the lower valve cover on the left bank and checked all the studs. Surprisingly there are no broken studs on the left side of the engine at all. I have more cleaning to do tomorrow before I may safely open the lower cover on the right bank to get the final count. I'm keeping my fingers crossed...

Somewhere along the line I thought you were doing a 3.0. 3.0 you cant see the studs.
Bruce

No 3.0L planned at this time unless I encounter something really nasty that is unexpected. The engine ran great prior to this exercise. Basically the oil leaks, plugwire popping off that one time from the broken stud and the infrequent cold start farts that I originally thought were carb related or this thing was top notch.


Lunchtime delivery... about 5 times as large as the original box that they sent that was mislabeled. I wasn't expecting these until 10/3 so now I'm feeling the pressure to locate a set of cam tools to get this thing done... I'm half way tempted to purchase the spring compressor tools myself to lap the valve and change the stem seals. If the other half of the engine does not have catastrophic failure evidence then I will probably pop for those.

http://i458.photobucket.com/albums/q...1/IMG_3028.jpg

Finally had a chance to go through my folder of receipts. The engine was built by Stephen Rogers of Leverett, MA with some labor paid to Dutcher Automotive in 1988. Work & Parts at the time (would be nice to get these prices back):

2.7RS Pistons & Cylinders - $1298
Gaskets & Hardware - 150
Rod Bolts & Nuts - $146
SSI Exhaust - $750
Chains - $48
Tensioners - $116
Locks - $16
Oil return Tubes - $80
PMO Webers - $1118
Cams - $350
Rod Bearings - $75
Main Bearings - $60
Oil Radiator - $175
Valve Covers - $75
Paint/Cleaning Supplies - $42
Stress Bar - $110
Clutch Face Plate - $140
Cam tower oil lines - $19
Alternator - $140
Knee Pads - $17.40
Labor - $1190 (Remove & Deliver motor, port cylinder heads, modify sheet metal heat synks, install oil cooler, Clean & Paint sheet metal, assemble & install engine)
Total $6116.30

There's more pictures but I thought these were worth a share mind you they are from 1988:

http://i458.photobucket.com/albums/q...9114103422.jpg

http://i458.photobucket.com/albums/q...1/IMG_0003.jpg

http://i458.photobucket.com/albums/q...1/IMG_0002.jpg

http://i458.photobucket.com/albums/q...1/IMG_0001.jpg

Took the right bank lower valve cover off tonight and no additional loose or broken studs found.

***I am now looking for cam tools if anyone has a set they aren't using ... otherwise I will purchase from the host on Saturday. ***

Finally have a chunk of time off from work - hoping to have the heads all off to the machine shop by the end of this week for valve job and guides.

The studs on the left side of the engine all came off easily; appeared to be blue locktite around the base of the stud rather than red.

The intake studs where the carbs mount are about a half inch short and did not come through the bolt with the carb mounted up and the exhaust studs look whipped... I'm going to have the machine shop swap those all out as they're tooled and experienced for any breaks during extraction.

Ordered new rocker hardware and RS seals to assist with the incredible leaks from the rocker bores... any leak after all this work would be unacceptable. The cam housing rocker bores are all smooth, tight and un-scored. Hoping to start going towards assembly in the next couple weeks.

Sealant thread here for organization when the time comes: http://forums.pelicanparts.com/911-engine-rebuilding-forum/284737-complete-engine-sealant-thread-12.html