Engine rebuild : head studs question

[kamaro]

Hi guys, I'm now rebuilding my '87 3.2 engine (180k miles, first engine drop), I got one broken lower head stud so I need to replace them all for a good measure. So I have a couple of questions:

1- how do you feel about using a set of 12 used upper studs that I removed from my other 3.2 case which I used ARP instead (was a boosted setup)? I heard that the 3.2 doesnt have any issues with the upper studs, just the lower dilavar ones. doing so would save quite a bit of the rebuilding cost.

2- Do I have to use new barrel nuts and washers for the head studs?

Thanks!

[brighton911]

I used a set of steel uppers in place of the Dilivars on my 3.4 with no issues at all. And no issue in re-using the barrel nuts and washer too.

[Turbo_pro]

Supertec head stud kits are the best option for all air-cooled 911 engines.
There are other options that work but none of them offer the benefits of the Supertec head stud including ease of assembly and life time warranty.
They are available from our host.



https://www.pelicanparts.com/More_Info/SPTCHSK1.htm?pn=SPTC-HSK-1&bc=c

[kamaro]

Supertec are awesome but at $1300 they are beyond my budget, after all its a stock 3.2. I believe the uppers are steel and have no issues, so I think I will buy a set of 12 steel studs from the host to replace the lowers only.

[Turbo_pro]

Originally Posted by kamaro

Supertec are awesome but at $1300 they are beyond my budget, after all its a stock 3.2. I believe the uppers are steel and have no issues, so I think I will buy a set of 12 steel studs from the host to replace the lowers only.

I assume your issue is shipping because the Pelican retail is only $ 830.
You might try contacting Henry @ Supertec for better pricing.
Do you guys have a tariff on US made parts?

What's that old saying? Not enough money to do it right but plenty of money to do it over?

[kamaro]

Originally Posted by Turbo_pro

I assume your issue is shipping because the Pelican retail is only $ 830.
You might try contacting Henry @ Supertec for better pricing.
Do you guys have a tariff on US made parts?

What's that old saying? Not enough money to do it right but plenty of money to do it over?

of course shipping will not be cheap, but I mean it will cost $1300 by the time you buy the nuts and washers with the stud set. Also add a %10 tariff. What I meant in my last post is do I need something like supertec studs for a stock 3.2?, I hear very good things about the Canyon brand steel studs and they are 1/4 the price.

[Turbo_pro]

Originally Posted by kamaro

of course shipping will not be cheap, but I mean it will cost $1300 by the time you buy the nuts and washers with the stud set. Also add a %10 tariff. What I meant in my last post is do I need something like supertec studs for a stock 3.2?, I hear very good things about the Canyon brand steel studs and they are 1/4 the price.

Supertec head stud kits include 24 studs, the nuts, washers assembly lube, loctite and jam nuts for ease of installation. Tariffs are just a cost of government.

Canyon studs are good quality but a different material than stock studs. That means you need to replace all 24 studs. Pelican price is $28.25/ea. x 24= $ 678 and it doesn't include nuts and washers.

I just checked with Henry and his direct price is $100 lower than the Pelican retail.

[Magyar Kiwi]

Hi
For a stock engine I would be happy to reuse 12 factory upper head studs, and all nuts and washers following a close visual inspection for corrosion and damage.
They are a quality items with a proven track record.
Hope this helps.
Cheers

[mikedsilva]

Originally Posted by kamaro

of course shipping will not be cheap, but I mean it will cost $1300 by the time you buy the nuts and washers with the stud set. Also add a %10 tariff. What I meant in my last post is do I need something like supertec studs for a stock 3.2?, I hear very good things about the Canyon brand steel studs and they are 1/4 the price.

I think Henry himself mentioned that the Canyon brand are good to use since he knows who makes them and what composition they are.
For a stock 3.2, I'd happily use those or generic steel studs but I would replace all 24 for piece of mind.

I have taken apart 3.0 and 3.2 that have had broken top studs too.

[PeteKz]

Mike has more experience with 911 engines than I do, but I have not yet seen upper broken studs on the dozens of 911 engines I've looked at with valve covers off. Thus I would want to know more about those that had broken upper studs. Were the lower studs broken too? I would expect so, and I suspect that continuing to run the engine for a long time with the broken lower studs thereby put more stress on the upper studs, leading to their failure. Was there also leakage at the head/cylinder surface? Corrosion of the studs also would have contributed to their failure.

I agree with Magyar. No need for expensive race studs for your engine. Remember, the upper steel studs in your engine are "used" too. If you already have a set, I would put them in the bottom row. Used nuts and washers are fine too. One caveat: If any of the studs have corrosion pitting, then don't reuse those. And to prevent future corrosion and possible cracking, paint them before installing.

[Turbo_pro]

Race hardware? Replacing the Dilavar is necessary. Replacing them with quality hardware is hardly a "racing" upgrade.

[PeteKz]

The Porsche studs are completely satisfactory. After all, they last 100's of thousands of miles in stock engines. And they cost a hell of a lot less. Not knocking Henry's studs, but they are overkill for kamaro's purposes.

[Turbo_pro]

Without trying to argue or create a head stud advertisement, I would suggest that the engineers at Porsche decided that the head studs they designed in 1963 were not "completely satisfactory" to handle the additional stresses of higher horsepower developments.

Quick question: How would you feel if your wife described your marriage as "completely satisfactory"?

As far as I can tell, depending on where you buy your studs, the Supertec studs are only a couple of hundred more than Canyon or even stock steel studs. They are 100s less than ARP and Raceware and half the price of Dilavar.

[85RedCarrera]

+1 on Supertec head studs. They also are guaranteed not to break.

[PeteKz]

Hey, it's your money, so spend it however you want. The OP asked about reusing the used OE Porsche studs he already has. I see no good reason not to, subject to the caveat about corrosion.

As for marriage being completely satisfactory, after 30+ years, I won't ask that question...

[Henry Schmidt]

Head studs on air-cooled 911 engine builds is always contentious.
Of course I like Supertec studs and we use them in every build.
Everyone should get to make an informed choice, so my only advise is to use all 24 stud from the same manufacturer. In the case of SCs and Carreras where the top studs are steel, I recommend you replace those as well as the Dilavar lowers. The top studs have unknown mileage and unknown heat cycles so their physical properties will be different from any new stud you install. I've been a champion of the importance of equal champing forces to create the most stable head to cylinder configuration possible.
24 matching studs is your best chance at successes. .

[PeteKz]

The material properties of the steel head studs in a Porsche air-cooled engine do not change due to time, mileage, stress cycles, or heat cycles. The temperature that a steel stud would have to reach to change its material properties is far higher than it could experience in use.

IIRC, SAE Grade 8 steel bolts are heat treated around 800F. I expect the steel head studs are made to similar specs. To change the material properties of the heat treatment would require the stud to get close to that temperature, so let's be conservative and say 500F. Remember that the studs are in the airflow under the shroud. So they don't get as hot as the exhaust side of the head. Either the heads, valves, cylinders or pistons would fail and the oil would be cooked long before the studs could get to that temperature range.

If there is mechanical damage to any of the studs, including corrosion pitting, then absolutely change them. Otherwise, there is no mechanical reason not to reuse them. Follow Henry's recommendation to use the same studs all around (even though Porsche originally used Dilivar on the bottom row and steel on the top row from 78-on).

[Henry Schmidt]

Originally Posted by PeteKz

The material properties of the steel head studs in a Porsche air-cooled engine do not change due to time, mileage, stress cycles, or heat cycles. The temperature that a steel stud would have to reach to change its material properties is far higher than it could experience in use.

IIRC, SAE Grade 8 steel bolts are heat treated around 800F. I expect the steel head studs are made to similar specs. To change the material properties of the heat treatment would require the stud to get close to that temperature, so let's be conservative and say 500F. Remember that the studs are in the airflow under the shroud. So they don't get as hot as the exhaust side of the head. Either the heads, valves, cylinders or pistons would fail and the oil would be cooked long before the studs could get to that temperature range.

If there is mechanical damage to any of the studs, including corrosion pitting, then absolutely change them. Otherwise, there is no mechanical reason not to reuse them. Follow Henry's recommendation to use the same studs all around (even though Porsche originally used Dilivar on the bottom row and steel on the top row from 78-on).

You're missing the point. Not all steel is the same. Not all manufacturer have the same thread processing (some cut some rolled) or the same material spec or heating treating process. Those processes matter when equal clamping force is the goal.
Unless you are willing to have your old/used studs analyzed, why risk it?
The head studs on many 911 engine are enclosed by the cylinder so they are not exposed to the cooling air. Heat cycles on stressed hardware matters.
As for Porsche's choice to stagger the head studs on 78-on, that is an inaccurate statement. All 78 and later 930 Turbos, 964 and 993 engines used the same stud top and bottom.
The use of staggered studs was an attempt to mitigate warranty issues and was never designed as anything else.

[dannobee]

Pete, the problem with Dilavar is intergranular corrosion, baked in during the manufacturing process.

Ask any of us who were around when the Dilavar studs came out. We'd pull apart engines for various reasons and see broken studs, then go to the parts counter and get a new set. Install them, torque them up, then come back in the morning and see that a few had already broken. Brand new factory studs, torqued to factory specs, by factory trained technicians, and now forced to re-do the job before the engine was even started.

After seeing this first hand a few times, it's no wonder why those of us who have been around awhile are gun shy at using Dilavar studs, much less reusing them. Oh, and the steel studs would sometimes break, too, but at least they'd break after the engine had some miles on it.

[PeteKz]

dannobee, yes the Dilivar studs were a bad experiment. I had two broken lower studs on my SC engine (w 64Kmi) when I rebuilt it 30 years ago. No more Dilivar for me after that. Please distinguish that I do NOT advocate reusing Dilivar studs--pitch them directly in the trash bin. I only advocate reusing Porsche steel studs, the same on the top row and bottom row. As Henry corrected me (thank you), Porsche didn't use Dilivar on all the 78-on engines, 930's being an exception, and I should have said '78-'89. And, as I have cautioned several times, only reuse them if they do not have mechanical or corrosion damage. Other brands of studs I'm not sure about.

There's another reason I advocate reusing parts: Those parts have proved their durability in actual service. They have passed the "infant mortality" phase during which manufacturing defects will usually manifest. That doesn't apply to all parts, only those that do not get mechanical wear from their use. E.g., I do not advocate reusing worn synchro rings in the transmission, or oil pumps in the engine, or visibly worn rocker shafts/bushings, or some other parts, unless they measure within service specs. If those measurements are good, then reuse them.

P.S. I'm still looking for the measurement of a new timing chain, between 20 or more pins in the chain. I want to compare that to the 4 used chains I have in my parts collection to determine how much wear timing chains get in service. The four chains I have are the same length, even though they have different miles on them, so at this point, it doesn't look to me like they wear significantly. I've also noted that on my engine the cam timing didn't change measurably in 20,000 miles. If the chain and/or sprockets were wearing/"stretching", the cam timing should change. Maybe it takes a lot more miles for that wear to become noticeable.