Engine rebuild manual / broken head studs

Ove · 10-09-2002, 06:55 AM

Just found out that two of the head studs on my '83 3.0 engine are broken. It only has around 70.000miles on the clock (115.000km). Is this a common problem at this milage? My guess is that they may have been torqued to the wrong spec. by a previous owner.

At the price I was quoted to fix it I could probably buy a used 3.2 engine.
The "good" news is that the winter is here in a few weeks, and I was not going to use the 911 during the winter anyway. Which means I've got 6 months to do this job. I have a lot of mechanical experience, but have never worked on a 911 engine.
Guess it's time to start now.

Please help me find a good engine rebuild manual and give me some advise on other work I should do while I'm "in there" anyway. What do I need to replace? Probably cylinder rings, rod bolts, rod bearings, I know the heads will need to be resurfaced need cylinder rings and I am also upgrading to hydraulic chain tensioners. Other upgrades to get more HP? And can anyone recommend some good quality head studs? Woudn't want to do this job more than once!
I know there are other threads on the subject, but I still have these questions.

Thanks

Jadams1 · Jadams1's Garage

The failure of the studs is more of a corrosion problem, not miles.

Here's an option. I had two broken head studs on my 80 SC too. My engine had 107,000 miles on it and ran strong with no symptoms at all. I replaced all 12 lower dilivar studs with steel ones, replaced all the gaskets and put it all back together. The car runs great and I don't have to worry about driving and damaging my heads from beating against the cylinder.

I did the chain tensioner upgrade at the same time too. Our host provides all the parts you need. The parts came to around $750. You'll also need some special tools to tighten the camshaft nuts, that's another $100. Wayne's book will be out soon too. I did mine using the Bently manual,Pelican tech tips and the expertise of people on this board.

Superman · 10-09-2002, 07:36 AM

Virtually no one has ever been able to take heads off, replace studs and just bolt it back together. Doug Z will remove his engine on Saturday (I'll be there as a safety monitor), but he's thinking about 3.2 P&Cs.

Anyway, yes you can remove and disassemble your engine, and we will help with all the advice you will need. Or, you can find a replacement engine, but you never know what problems that engine may have or develop. If I were going to install a replacement engine, it would not be a wimpy 3.2 It would be a ferocious 3.6.

Early_S_Man · 10-09-2002, 07:36 AM

Ove,

I don't think it is mileage that is the primary factor for the Dilivar studs breaking ... years and exposure to moisture seems to be the determining factors. It has been going on in the USA since about 1996 ... in selected parts of the country ... seacoasts, rainy regions, snowbelt, etc. I have heard of others encountering the prolem in as little as 60K - 70K miles.

We 'hear' that there is an engine rebuild book lurking about the premises, here ... any day, now!

Doug Zielke · 10-09-2002, 01:43 PM

Quote:

Originally posted by Early_S_Man
We 'hear' that there is an engine rebuild book lurking about the premises, here ... any day, now!

Yasss...harumphhh......just *where* is that danged book, anyway?

Ove · 10-09-2002, 03:04 PM

John, Superman and Warren,

Thanks for your replies.
I will buy the Bently manual for now to get started, and of course Wayne's book later. In fact I think I'll wait for Wayne's book to come out before I start working.

I agree that a replacement engine could have problems too. The one I have runs great, so I will keep it and carry out the work needed. I also think I would be afraid to reassemble the parts without resurfacing the heads and without doing the other stuff "by the book". Good to know that there are people like you on this board to turn to when I need help.

I'd love to have a 3.6, but was going to improve other things first (suspension, brakes, interior) before I did an angine upgrade. It is tempting, and I could probably raise the money to buy one during the winter, but I belive this swap involves more work than just removing the old engine and putting the new one in. Besides, I would have less money to improve the handling of the car...

Regarding the studs, I guess I should buy a set of high quality steel ones. Which brand do you recommend?

Any advise is welcome, let me know what you think.

911pcars · 10-09-2002, 04:45 PM

Ove and John,
Off hand, do you remember the color of the broken head studs?

Silver, Gold or Black?

Thanks,
Sherwood Lee
http://members.rennlist.org/911pcars

Ove · 10-09-2002, 06:03 PM

Serwood,
Silver, I think, definetively not gold. I have them in my car, will check tomorrow to be sure. What can you tell from the color?

Doug Zielke · 10-09-2002, 06:29 PM

Quote:

Originally posted by 911777

Silver, I think, definetively not gold. I have them in my car, will check tomorrow to be sure. What can you tell from the color?

There were several versions of the infamous Dilavar studs. Some were silver in color, some golden, and some had a (black?) epoxy coating on them. All of these platings/coatings were attempts to prevent the corrosion problems that cause premature failure of the stud.

Which one is "best"? Who knows? Bruce Anderson has reported failures in all types of Dilavar studs.

911pcars · 10-09-2002, 07:11 PM

Just conducting a seat-of-the-pants survey of which Dilavar head studs have a higher frequency of breakage. Trying to determine whether its a combination of corrosion and/or its combination of steel studs on the upper half (different coefficient of expansion). All Turbo head studs (24) are Dilavar but I don't have any feeling for how frequently they break in these engines.

Silver, gold and black were the progression of Dilavar studs. Yes, the black ones are epoxy-coated.

Sherwood Lee
http://members.rennlist.org/911pcars

Ove · 10-09-2002, 07:58 PM

What do you think of the raceware studs? Expensive for sure, are they worth the money? Other options?
What would you guys use if you were to rebuild my engine?

http://www.raceware-fasteners.com/prod01.htm

http://www.pelicanparts.com/catalog/shopcart/911M/por_911M_enginB_main.htm

scarebus · 10-09-2002, 11:17 PM

Ove,
I finished rebuilding my 3.0 euro engine 2 months ago. I used ARP head bolts/nuts and rod bolts/nuts, plus racing valve springs. Did a little filings on case and cylinders. The pull after 5000 rpm is
great. 'Performance Handbook' by Bruce Anderson gives you lot
of options and ideas.

Bobboloo · Bobboloo's Garage

For what it's worth. The 3.2 motors also came with the dilivar lower studs also.

If it were me I would just replace with the factory steel studs resurface the heads and button it up. Your mileage is so low. You can pull the cylinders and pistons off together once you pull the wrist pin so your rings will remain seated. Why rebuild an otherwise healthy motor?

If your into modifying then why not start with a buildable core. You could sell your motor to recoup some of the money spent on mods.

Possible mods:

98mm P+C 9.8:1 CR
964 cam grinds
SSI exhaust.

Or the shortcut, put in a 3.2 as you previously suggested.

Bobby

Wayne 962 · Wayne 962's Garage

They are FedEx'ing me part of the layout tomorrow - seems to be coming along faster than expected.

If you buy a 3.2, you will be out $6500, and then will probably have to rebuild that engine soon, for a total of about $15K...

-Wayne

Jadams1 · Jadams1's Garage

If your going to keep your 3.0 stock, just replace the bottom twelve dilivar studs with the steel studs that are used on the upper row. They cost around $11 each.

Cylinder Head Stud-Upper
C-101-172-00

Ove · 06:57 PM

Thanks for the tips,

Seems like I will be allright by replacing the studs with steel ones and resurfacing the tops as Bobboloo suggests.
It would be less expensive for me to get a new engine here than it would be for you guys in the states. 12 hours and I could be in Germany to pick one up. But if it needs a rebuild it will not be worth it. Parts are expensive here, and for all I know it could be in worse condition than the one I have.

When I was talking about rebuilding I was not thinking about doing the whole engine, just doing the work related to installing new studs. Sorry for the confusion. Chris - thanks for the tip, I have the 'Performance Handbook' and will read it before I start working.

The previous owner told me that the engine might have the "S" cams, but he had not been able to verify this. This is why I suspected the reason for the stud failure to be that someone had worked on the engine and torqued the studs to the wrong specs. Never occured to me that corrotion could do this.
Compared to a friend's 911, also with a 3.0, it pulls stronger at high revs. He would say it's because my car is weaker at low rpms of course...

There is a noticable change in power once it gets above 3500 RPM. My friend's car pulls more evenly as the revs rise. To me this (and what the p.o. said) indicates that the S cams are there. Is there a part no. I could look for or another way to tell what cams I have while I'm working on it?

Ove · 10-17-2002, 03:14 AM

Here they are.
The studs are silver, one of them may look golden, but that's just surface rust...

Jadams1 · Jadams1's Garage

The dilivar studs on my 80SC were gold. They broke at the camtower/head area. The two that boke were at cylinder #1, lower right and #6, lower right.