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Cylinder head studs replacement questions

On my 3.2 hunt, I came across an 85 targa that the owner says needs cylinder head studs eventually. Itís not the first one on my list but other than that appears to be in great shape. Have to travel to see it.

Iím venturing into this as a hobby wrencher and a DIY guy where I can with proper practices and standards. .

In your folks assessments, how insane is this to tackle at home over a winter? How long can you drive it in itís current state, and what would the issues be leaving it for say a season?

Iím in Canada and was wondering how much to budget or work into price.

Thx.
Old 10-03-2019, 10:35 AM
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i didnt realize 3.2s had stud issues too . but you can do it at home .. but i would not tackle it unless i was a pretty good DIY guy to begin with.
I did mine no problem but the most of the time was in the research up front and collecting the books and tools . If a PPI reveals they are all intact you are fine .. if it reveals they are already broken then you will have to rethink.

cost me about 4k CAD i think at the time in parts. my machine shop work was very minimal at 1K in that figure. i also did not split the case.

i could work indoors where it was warm so you have to consider that also.
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Old 10-03-2019, 10:39 AM
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I would find out if it already has broken head stud or two, or if the seller is just mentioning it as a possible future maintenance job. Unlike the SC, the 3.2 doesn't use head gaskets, so if it were driven very long with a broken stud or two, the sealing surfaces could get eroded and require machining and increasing the scope of the repair.
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Old 10-03-2019, 10:55 AM
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On the DIY side of replacing head studs, would you drop the engine and replace all of them or leave it in the car and just replace the broken ones? The exhaust studs are the ones that break, as the intake studs are still regular steel studs, so they would be somewhat accessible with the engine still in. If you have the engine on a stand, a simple socket wrench and propane torch was all it took for me and every single stud came right out. With it still in the car, you'll have very restricted access to the stud.
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Old 10-03-2019, 01:50 PM
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3.2's don't use head gaskets??
Old 10-03-2019, 02:14 PM
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Thx guys, ya it’s not my top car on the list but it’s in the price range. Machine work scares me and you guys bring up a great point. Good this to look for indeed. As for a PPI, I’d have to get one far from home in this case.
Old 10-03-2019, 07:31 PM
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There are only a couple of lower studs that are even possible to do without teardown.

No head gaskets on 3.2's. And like RedCoupe said, if it's been driven much with broken stud(s), it's gonna need the heads cleaned up and the cylinder(s) replaced/repaired.
Old 10-04-2019, 05:25 AM
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Sealing surfaces between heads and cylinders get "worn" regardless of whether the cylinders have the CE ring seal or not. It's the studs allowing the joint to shuffle that causes the wear and the CE ring seal does nothing to prevent it.

3.2 Carrera cylinders do indeed NOT have the CE ring and that's not necessarily a bad thing. They seem to seal better and are also more desirable. Typically the desire is on the used parts side of things, because without the seal ring groove, they are the better choice to have bored and re-plated for the 98mm bore (3.0 to 3.2 or 3.2 to 3.4) many people desire.

The lack of the CE ring groove provides a thicker area at the very top of the cylinder when the cylinder is bored larger. The belief is, the remaining thickness after a CE-ringed cylinder is bored larger is too thin, which can compromise the cylinder strength. I've seen these CE ring cylinders bored larger and it is quite thin there, and the plating chipped off which required me to have one of the cylinders re-re-replated during a rebuild

My set of cylinders are pictured here and sorry there's not a good picture in the group showing how thin the cylinder wall is Core Mahle Nikasil Cyls- 98mm SC style

I'd be curious to know what the seller's basis is for needing head studs soon. I'd have to assume signs of oil leakage at the head-cylinder location? Because broken head studs are easy to detect just by looking in the valve covers. Either a piece of broken stud (with the nut & washer still on) it is sitting in there, or there's no nut at all because someone took it out and figured, ah no big deal three studs are still holding it together Otherwise you can't see the lower studs anywhere else on the engine to assess their condition.

A 3.2's lower studs are black epoxy coated and all it takes is some compromised coating to allow rust to start, which will eventually lead to a broken stud. Here's how one of my studs greeted me when I was disassembling it for bad valve guides

your opinion on head studs

It's not practical to replace the stud in-place without some teardown because you can't get at the end of the stud with a tool to extract it. Nor do the studs want to release from the engine case due to the original installation which used thread locking compound. You also can't reset the new stud to the desired depth all that easily. Stud depth is important because of the goofy barrel nuts Porsche chose to use. Incidentally that stud depth issue can be avoided by using a different type of nut (flanged hex nut) but that's another discussion for another time. Basically you want to take off the heads so you know what you're dealing with. Like the guys said, you want to get a look at the head surface and the cylinder surface to see what amount of shuffling damage they do/don't have.

Simplest approach here is engine removal and remove the heads and cam housing as a single unit (leave all 3 heads attached to cam housing) which then leaves you with the exposed cylinders. Slide the cylinders up just a bit to leave the piston rings undisturbed so you can get at the wrist pin circlips. Remove a circlip (easier said than done) to allow the pin to come out and then you can leave the pistons in the cylinders and not disturb the rings. The rings are quite fragile and easy to break, so that's why you don't want to bother them. However, this can also be viewed as short-sighted because leaving them in the cylinders does not allow you to get a look at the rings to see if any are already broken. Nor can you check the ring grooves in the pistons for wear beyond spec. This is where the slippery slope can start to rear its ugly head.

Anyhow, once you get the pistons off the connecting rods, then you have the easiest access to the studs for any that need replacing. The reason you need the cylinders out of the way is because often a stud will be broken way down near the engine case. It never breaks at the top where the nut is installed. Obviously with the heads and cylinders installed on the engine, there's no way for you to get allllllll the way down to the broken stud to extract it.
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Old 10-04-2019, 08:49 AM
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I really want to know more about the plan to change head studs in the car....
Bruce
Old 10-04-2019, 08:56 AM
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I am pretty sure it cannot be done in the car. The cam tower has to come off, the heads and cylinders have to come off, cam shafts and rocker arms all have to come off. There is not enough room inside the engine compartment for all of that stuff to be removed. And even if there were room, the aggravation of constantly bumping your elbows against something and the compromises you have to make with the engine in the car will negate any time saving by not removing the engine,

How much time saving you ask? I can remove the 911 engine in 2 hours. Not enough saving to put up with the aggravation.
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Old 10-04-2019, 09:57 AM
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I really want to know more about the plan to change head studs in the car....
Bruce
Someone who wants to make the job as hard as possible/impossible.
Old 10-04-2019, 12:16 PM
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Cylinder head studs replacement questions

Stupid question here... how do you know your car needs head studs replacement?


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Last edited by OneMore; 10-04-2019 at 06:04 PM..
Old 10-04-2019, 12:49 PM
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yes, you can use 3,2 cylinder sealing rings.Here in Europe they do this on racing engines , i have mentioned that on some other post..her it is how it looks like
i did that on my last engine i did....
Ivan

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Old 10-04-2019, 12:52 PM
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One more - like most of us, this statement caught my eye. There is no such thing as knowing when you need to replace head studs other than the obvious - one or more broke. A proper advertisement might say "has two broken head studs, but still runs OK" or something like that. So you know - you roll the dice running that engine before you tear the top end off to replace the broken stud/studs, or all of them for good measure.

That is the question for the prospective buyer to ask the seller - what do you mean by that statement? Does it have a broken stud already?

In the fullness of time, a stud might break. Just as valve guides don't last forever, and need replacement. Some items may have an informal replacement schedule - replace the oil filter every time you change oil. In race cars, a variety of parts get replaced on a schedule - the idea is to catch things before they break, even if they seem good. But some of these engines will live their whole life without ever breaking a stud.
Old 10-05-2019, 08:06 PM
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Stupid question here... how do you know your car needs head studs replacement?


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Either the nut falls with a piece of stud falls out when you remove the valve cover or you put a socket on the bolt and it just spins.

I saw a 3.2 get one new head stud. The rest looked fine. The heads and cam covers were installed and tightened down. The next morning I walked in and two broken studs were lying on the floor. As I was standing there, I heard a "ping" and a piece of stud launched about two feet in the air and fell to the ground. Never reuse Divlar studs. Engine got all new.
Old 10-06-2019, 03:48 PM
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Thanks for your responses guys.


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Old 10-07-2019, 03:21 AM
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You should figure it as a 7 K job at a shop, including a full valve job. Once done, if the rest of the engine is in good shape, you could be good for 100K miles.

Many engines will need a valve job between 80,000 and 130,000 miles. With a higher miles engine, it is always good to know that a valve job has been done, as it kills two birds with one stone. Get a copy of The Used 911 Story by Peter Zimmerman. You need it.
Old 10-07-2019, 03:53 AM
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I really want to know more about the plan to change head studs in the car....
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Yeh right, insanity
Old 10-07-2019, 06:39 AM
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