Head studs - tear down question

[tripm]

I know this topic is beat to death on here, but I couldn't find the answer to my specific question.

1980 911sc

If I am ONLY replacing the bottom studs on both sides, what HAS to come apart? I have Waynes book and the manual, and I had advice from the shop I sent the car to for a 'tune up', but I can't find the answer.

The book has a complete tear down for engine rebuilding, the shop said 'everything but splitting the case' has to come apart to do the studs. Why can't I just drop the motor, pull the jugs and pull the studs? Do the pistons really need to be removed?

That's my question, but if you need more details, here is why I ask.

This car has been sitting for 10 years. It was rebuilt just before it sat. It has all common upgrades and was rebuilt by a reputable shop. I have spent spare time over the past two years replacing the fuel system, tires etc. to get it on the road. Everything was all set, but it sputtered. I brought it to a shop for tuning the cis, but they suspected something else and they were correct - broken head studs. Their estimate, and I'm sure it was to do more than just the head studs, was 8999.00.

I want to do the absolute minimum amount of work to replace those bottom head studs. If it blows up two days after I fix them, I can deal with that, but since it was rebuilt, I'm not expecting it.

Thanks for the help!

Mark

[euro911sc]

I'm not the expert, but you should be able to get the studs off after removing the heads, provided that the broken ones can still be gripped above the cylinders. If not then you can remove piston & Cyl together and not split the case. Though, most of the work will already be done... so splitting the case would be pretty much the last step of disassembly. I think you can also remove the heads all at once by bank by leaving the cam towers on them... Others may know more on this.

The above is useless if you pulled it out of the case... then the case needs to go to the shop etc etc etc

Best regards,

Michael

[briankeithsmith]

I guess my question would be, if the engine has theoretically just been rebuilt, why are the studs broken????

Seems to me that if they weren't broken at the point of rebuild, then something significant has occured since that time...

Either wayym as Euro911SC said, pull the heads, and you've got your studs there....

[tripm]

So do I need to take the timing change etc off in order to get the heads off? I guess I need to just dig in and do it.

<>

The rebuild was 15 or so years ago, but then the car wasn't driven much, then sat for 10 years. My guess is that they were corroded and snapped when the car was coming back to life over the past year. Starting, testing, stopping etc.

[briankeithsmith]

OK. I'll buy that. I guess corrosion could set in. I hadn't thought of that...

[cstreit]

If the studs are broken you will probably have to remove the cylinders... ...and it's much easier to put the pistons in the cylinders on the bench vs. while attached the rods. However if you can remove the studs without removing the pistons and cyl's I'd do it that way. No worries about replacing rings/seating then.

You'll have to remove the induction, shroud, heads and cam towers (togther) and take the timing chain sprockets off. You won't be removing the timing chains entirely.

[Groesbeck Hurricane]

I would add that if the bottom ones broke, I'd also replace the top ones. Cheap while your in there insurance.

If this is a street car, please read about which studs to use. I went back with all steel, but that was me.

[mede8er]

Originally posted by Groesbeck Hurricane
I would add that if the bottom ones broke, I'd also replace the top ones. Cheap while your in there insurance.

If this is a street car, please read about which studs to use. I went back with all steel, but that was me.

+1

[rlane]

No expert here but I think you can do this (based on my recent rebuild)
Once the engine is dropped, pull the CIS system as a unit (not too hard)
CAREFULLY remove the heat exchangers/exhaust-Search and read threads on ways to try and avoid breaking exhaust studs.
You can remove the cylinder banks/heads/cam carriers as a unit (left and right side) after undoing barrel nuts on the head studs and cam timing sprockets etc but you can't (I don't believe )remove them this way if you want to keep the pistons in the cylinders (which if you have Alusil you may well want to do).
I think some of our real pro's will weigh in on this but my gestalt is you should , for just a little more effort do a proper top end rebuild, get new studs in there with good technique. I would look closely at the pieces of broken studs that came out...there is 135 mm of stud above the case surface so you caqn easily estimate how much stud is available to grip.
Also several have alluded to the oddity of having head studs go bad with so few heat cycles after a rebuild. The well known Dilavar issues probably should have been addressed then...makes one wonder what else was not done...and if it was my engine a good tear down and inspection would be my cjhoice

[Eagledriver]

You are correct in only needing to replace the lower studs. The upper studs are already steel and almost never break. You can keep the pistons in the cylinders by only pulling them enough to get at the wrist pins. That is how I normally pull them and re-install them anyway. As far a chain housings and stuff I'd start with the cam sprokets and see if I could wiggle the heads and cam towers out with the rockers and cams still installed. Don't know if this is possible but give it a try. You can always stop and remove some more stuff.

-Andy

[Groesbeck Hurricane]

Were the lower studs steel or dilaver after the first re-build that sat? I still say, it is cheap insurance to replace the uppers, but I'm not an expert and this is not my car. Oh, by the way, one of my upper steel studs was broken not just the dilavers when my engine came apart.

[tripm]

I know the two that broke were dilavar, but the motor is still together so I'm not sure what else is there for studs.

And thanks for the note on your upper being broken - that's the first one I've heard of. Now that's all I'm going to think about. Errrg.

This car is going to drive me crazy. I keep going back and forth between stuffing it back in my garage for another few years and running down to the garage and not coming out until it's fixed.

[914efi]

I am just finishing this job. My approach was the same as rlane, do as little as possible, just fix the problem. One thing that makes this approach tough is that it is hard to keep everything clean since you can't easily wash off grime without getting it where you don't want it. It just adds a bit of extra time being careful. Clean as much as possible before cracking open.

I took the cam housing off without removing the cams, rockers, etc but the chain cases have to come off first. All of my rocker shaft hex bolts were very rusty, so it was not practical to take them out anyway. Heat the pistons with a heat gun to get the pins to slide (tap) out and remove the cylinders without taking them off the pistons.

Studs can (will) be a bear to get out. Some of mine were broken very close to the case, I welded nuts on them to remove the short ones. The heat from welding is needed to break the threadlock anyway. Some of them required ~10 tries with the nuts breaking off if not welded just right. Very tedious.

You probably have the advantage of the engine not having run after stud breakage, so hopefully no damage due to looseness of heads. I understand it was not unusual for the dilivar studs to break spuriously, assuming that is what was put in.

Re-assembly is the reverse of taking it apart. I'm starting mine this weekend, so hopefully this is all good advice!

[Groesbeck Hurricane]

FWIW as a data point, the chances of the steel studs being broken is VERY slim. I'm just a bit anal about these things...