Do 3.2 Dilivar exhaust head studs snap like the 3.0?

[GaryR]

Uhhh, yes they do!

From an 87 3.2 I am rebuilding.. these fell out, never touched them with a wrench. Kroiling the heck out of the remaining ones but I bet they snap too..



I believe the 4th from the left is a replacement Dilivar stud, looks newer and has more thread length, and THAT snapped too! 5 of those were on one side, 3 on the other, all exhaust.

[GH85Carrera]

I just rebuilt my engine. Not one head stud was broken. Two studs were loose. They just backed out with no effort. New ARP head studs match the pretty new ARP rod bolts.

Th reason for the rebuild was the loose head studs. They allowed a slight head leak. It needed to be surfaced and if ya do one ya gotta do em all.

[Bob Kontak]

Believe all Dilivar studs are prone to breakage - based on reading - not experience. 3.0 more so. Maybe has to do with a different protective coating

They shear.

You need heat to melt the thread locker. Kroil won't do the trick- although, it can't hurt. How much heat I don't know as I chickened out and took my case to a machine shop and paid them to remove. I did not have the collet type remover and was not sure propane was hot enough.

[Bob Kontak]

Originally Posted by GH85Carrera

New ARP head studs match the pretty new ARP rod bolts.

Those are sweet. I remember the Raceware ones I put in in 97. They were intoxicating to look at. Maybe that's why it took me so long to get finished. :-)

Question - are the ARP rod bolts stretch bolts?

[GaryR]

Bob - i'm Kroiling the nuts on the remaining studs, not the case end. I don't have high hopes of the last 4 exhaust studs not snapping when I go to remove the nuts but at this point it doesn't matter, just hope they snap with a couple inches left for the stud remover to work. The longer broken studs in my picture, they most likely will be drilled out by the machine shop my heads are going to. Since I have over 10 4mm bolts to be drilled out/tapped by the same shop (shroud) in the heads and other places whats a couple more!

Originally Posted by Bob Kontak

Believe all Dilivar studs are prone to breakage - based on reading - not experience. 3.0 more so. Maybe has to do with a different protective coating

They shear.

You need heat to melt the thread locker. Kroil won't do the trick- although, it can't hurt. How much heat I don't know as I chickened out and took my case to a machine shop and paid them to remove. I did not have the collet type remover and was not sure propane was hot enough.

[slow car]

Hi i have just pulled my ROW 3lt down (Yesterday ) and no studs broken BUT 4 head nuts were loose? and the head gasket was blown.
All my studs are steel. I put a straight edge along the top of all the studs to see if any had pulled and they were all with in 1mm.
Any light on this ? Maybe they were just left loose?maybe they are stretched? Do the steel stretch? can you re use the steel studs ?
John

[r-mm]

One mans experience pulling dilvar 3.2 studs: no heat required and double nutting provided plenty of torque to back them out. However even after lots of cleaning, chasing and compressed air blasting, the new steel studs were a bit sticky on the install.

[Reiver]

Was the car/engine a garage queen? Driven sparingly and short tripped?
I've had more P Mechanics tell me they see the head stud issue mostly on cars not driven to temp that sit around allowing rust to do it's job on the studs.
I traded my '83 SC lump out at 230k miles with all studs intact and never opened...ran very well (but did burn some oil).

[GH85Carrera]

Originally Posted by Bob Kontak

Those are sweet. I remember the Raceware ones I put in in 97. They were intoxicating to look at. Maybe that's why it took me so long to get finished. :-)

Question - are the ARP rod bolts stretch bolts?

Yes, they are stretch bolts.

[Tippy]

Put in 993TT head studs and never look back. I believe they are dilavar.

[nicfranc]

It seems very strange how some of these engines will have broken head studs and then there will be engines like my 1980sc with 300,000 miles and no broken head studs and still running very strong with no burning of oil. My engine has never been opened or had the top end done.
This can't just be the luck of the draw.
Perhaps something happened when the engines were assembled in the factory.

The previous owner of my car put most of the miles on it and ran the hell out of the car
commuting to work as a daily driver. He did not baby it but he did maintain it properly.
The car was garaged most of the time but also spent a few years outdoors.

[Geronimo '74]

Originally Posted by GH85Carrera

I just rebuilt my engine. Not one head stud was broken. Two studs were loose. They just backed out with no effort. New ARP head studs match the pretty new ARP rod bolts.

Th reason for the rebuild was the loose head studs. They allowed a slight head leak. It needed to be surfaced and if ya do one ya gotta do em all.

Rebuild, Glenn?
Good luck.
Did you have any issues with it?

[GH85Carrera]

Yea, G-man. Full rebuild. It was a lot of "while you are in there" decisions.

Last year after I drove home from Michigan I was checking out the car and noticed one head was wet. The only way it could be wet was a head leak. Yank the engine and inspect and the only way to KNOW what the problem is is to take the head off.

The only cure for the leak was a little machine work on the head. If one gets cut they all have to get cut. If the heads are off it would be stupid to not do a top end. Since the cylinders just slide off it is a good time to check the rings. They are worn and need to be replaced. At that point just a few more nuts to remove and the case can be opened to check it out.

It was a smart decision. One rod had a slight hot spot and of course the intermediate shaft bearings were worn.

All the tolerances were perfect so "while I am in there" new ARP rod bolts. And "while I am in there" a few more times and now the engine is all fresh and new.

The engine had 150,000 miles and over 100 autocrosses over a dozen DE track days and will be going to California in the summer. It was time.

[Ronnie's.930]

Originally Posted by nicfranc

It seems very strange how some of these engines will have broken head studs and then there will be engines like my 1980sc with 300,000 miles and no broken head studs and still running very strong with no burning of oil. My engine has never been opened or had the top end done.
This can't just be the luck of the draw.
Perhaps something happened when the engines were assembled in the factory.

The previous owner of my car put most of the miles on it and ran the hell out of the car
commuting to work as a daily driver. He did not baby it but he did maintain it properly.
The car was garaged most of the time but also spent a few years outdoors.

Another interesting element regarding the hit-or-miss dilivar stud situation is that there have been many reports over the years of new studs breaking while the engine was still on the stand.

[nicfranc]

Originally Posted by Ronnie's.930

Another interesting element regarding the hit-or-miss dilivar stud situation is that there have been many reports over the years of new studs breaking while the engine was still on the stand.

Makes you wonder if it could have been a manufacturing defect or improper installation
of the Studs. Weren't these installed by hand in the factory ?

[Dixie]

No broken head studs on my '88. I replaced the lowers just for insurance. I simply double nutted the originals and used the expected 'omph' to get them out. No heat was required.

Perhaps road salt and frigid temperatures have a role in stud durability.

[911pcars]

Originally Posted by GH85Carrera

Yes, they are stretch bolts.

Regarding your answer that ARP rod bolts are "stretch" bolts. Can you confirm with ARP info?

If so, then why would ARP recommend torquing to spec through several cycles? This would be equivalent to reusing factory bolts which are torque-to-yield (stretch) bolts.

So as not to confuse those who have an option to use alternative rod bolt fasteners.

Thanks,
Sherwood

[Bob Kontak]

Originally Posted by 911pcars

So as not to confuse those who have an option to use alternative rod bolt fasteners.

The reason I asked the question is that Raceware state their rod bolts do not have to be stretch bolts as they have 50 squillion pounds of tensile strength.

I checked two journals on my crank and replaced with new factory bolts back in the late 1990's

I have no skin in the game and am not a metallurgist, but I have always raised an eyebrow to the thoughts of not having stretch bolts on rods. This is only because this is what I see on all factory applications I come across.

[Jcslocum]

The ARP bolts are either or. They can be torqued, which elongates the bolt via the screw jack method of the thread. The torque is an easily measurable level of force but does have considerably more error in the actual residual load versus other methods, probably in the area of 10-15% scatter (difference between bolts) for this application. Measuring the stretch of the bolt with a rod bolt measuring tool is much more accurate than torque maybe 10x more with an accuracy of residual load of 1-2% scatter.



ARP Instructions

In critical applications, torque just isn't accurate enough and we use tensioners. When it's mission critical, we use tensioners and then measure the elongation of the stud/bolt with a calibrated dial indicator or ultrasonic device. This gives us the load verification that we need to guarantee bolt load/clamping force.

[boissymeis]

Maybe has to do with a different protective coating