broken head stud

[jsmithcds]

A little history for you. Three months ago I purchased a 1979 911sc from a fellow pelicanite. I asked a ton of questions and negotiated a fair price for the car he said he had. The car is 95% of what he described. A few minor things were left out. Not a big deal. That can be expected and you deal with it. Before the purchase I asked if he had done a ppi and a leakdown test.

Here is the response, "Hi there & thanks. Yes there was a ppi done. Compression was 135-140 in all cylinders with ZERO leakdown (test was done with 100psi in cylinders). It has the pop off valve, but not the chain tensioners. Has ssi's and new exhaust. I think it has the green bilsteins??? It's at my mechanic's shop in storage. Brakes are stock I think. Car is nice and drives beautifully. No one has looked at it yet. I have an interested party in Michigan. I misplaced the title so I'm waiting on it to come back from the state. Comes with the a/c stuff that was taken off. Let me know if I can answer any more questions. Thanks, Dan"

I brought the car home and drove it less than 75 miles and everything seemed good. I was happy with my purchase. It snowed 6 inches that night so it went into storage in my heated garage were I have spent the last three months tinkering and getting it ready for my first track day.

Monday night I went out to put the valve covers back on the car because i wanted replace the seals because of a small leak. To my dismay I found a barrel nut sitting before me. Upon further investigation I saw the pulled stud.

I have been asking for the results in writing for quite some time. The test was done by a certified Porsche Ferrari and Bentley mechanic in Pittsburgh. It was done in his private shop where he does work on the side. I visited his shop and talked to him about the car. I was told as recent as last Friday that the testing was done right before I made the buy.

The question is can you get these kind of results with a broken head stud? Compression was 135-140 in all cylinders with ZERO leakdown (test was done with 100psi in cylinders). Is this the correct procedure for testing by a certified Porsche mechanic? When i pulled the plugs they were extremely rusty Autolite plugs. I needed to switch to my big half inch wrench to get them out they were rusted in so tight.

Here are some pics of the stud. Does this look like a stud that was broken within the 75 miles? Would the car pass the tests with this stud pulled?

Before I let loose on these two I would like some opinions form my fellow Pelicanites. I feel that I may have been lied to but wanted your opinions first.






Thanks for your opinions....

Justin

[Tippy]

Im still trying to wrap my head around the Mechanic saying 0 leakdown, that is impossible.

[carrera turbo]

can you get good compression and leak down with one broken stud"YES"

was this stud broken when the ppi was done most likely as its very rusty and may have been lodged in the head.

not sure about the ppi but i always when im inspecting a motor put a light torque on the head studs. some simply look to see if they are all there.

my concern would be that all the other bolts are rusty as well

good luck ed

[Steve@Rennsport]

Looks to me that its been broken for awhile.

A proper PPI on these cars should include a check of the head studs as those have been problematic since 1978. That said, I don't see very many good PPI's being performed as I suspect few folks are willing to pay the shop time to thoroughly go over each and every item that should be covered.

Its pretty difficult to challenge an owner that simply may not have heard or noticed anything awry and as Ed wrote above, these don't always show up on compression or leakdown tests. One really must put a wrench on each head nut during the inspection to ensure integrity.

Without question, one should replace all of them for reliability. I would offer that anyone considering the purchase of these excellent automobiles factor the cost of replacement if there are no written records of this being done.

[john walker's workshop]

makes you wonder if any tests were done with the plugs almost seized as you noted.

[rluciano]

I had a PPI done on an SC that had 140-150 compression and 2-5% leakdown. Then valve covers were pulled for a valve adjustment and broken head stud, just like yours. I backed out of the deal. I've yet to see my deposit back, but ...

Good compression and leakdown are certainly possible with a broken head stud. But how long will it last is anyone's guess.

[911pcars]

I too would suspect 0% leakdown on all cylinders. It just might be possible on a just broken in engine, but not probable. Highly unlikely on an engine with several thousand miles behind it.

The rust on the stud, as noted, shows this has been broken for awhile. Unless the PPI specifically included removal and inspection of the lower valve covers, it's difficult for the inspector to have caught this.

I would have chosen my own independent repair shop to conduct a more objective PPI. A Porsche specialist might have suggested removing the valve covers given the history of head stud failure on 3 liter engines.

A repeat compression test might reveal whether it indeed had been tested at the compression pressures quoted previously.

Sherwood

[diverdan]

Only one broken stud? Probably wouldn't affect leakdown. Plugs tight due to the fact that they weren't taken out? Hmmmm. I'd be inclined to see if there is any evidence that the cam covers weren't off recently. Yes, that stud has been broken for some time and rust is evidence that it wasn't leaking. Good luck and I hope you are a DIY kind of guy, otherwise it is gonna cost.

Dan

[sc_rufctr]

All great information but what should this guy do now to get his car back on the road as quickly as possible?

[carrera turbo]

he can tear down replace all head studs.

put a torque wrench on all other studs drop torque vales a few pounds see how many if any other break. if no others break he could drive easy at a risk .

not recommended, but i have a high mileage 3.0 that is on its second season of two broken head studs, and i have been watching it close and driving quite a bit as a test. this is not recommended but i have a fresh 3.0 sitting aside for the day i hear the psst pssst pssst.

the rust is a real concern i would be hesitant to drive much longer.

cheers ed

[Nine9six]

I dont believe thers is such a thing as 0% leakdown!!! The simple physical configuration of an internal combustion engine would lend credence to this since the rings are not a complete seal. With that in mind, how could you pressurize an internal combustion engine cylinder and expect zero pressure leakage?
Compression and Leakdown are two separate and distinct tests, with 0% leakdown being a physical impossibility predicated upon piston & ring configuration.

[john walker's workshop]

leakdown on a fresh or very good engine is around 4%. i've seen 2% occasionally but that's unusual. compression on a 3.0 should be around 150#.

[burgermeister]

Sounds like the seller paid for the PPI?

I think it was a sloppy PPI (and I too have suffered from the aftereffects of one), but it's hard to say if any malice was involved. The first time you're likely to notice a broken stud is at the next valve adjustment.

It's life when buying a used car. I'd get over it, pull the motor, and replace the studs, yucky as it sounds. You've got a fair shot at getting it back together before driving weather arrives ....

[carrera turbo]

Originally Posted by john walker's workshop

leak down on a fresh or very good engine is around 4%. i've seen 2% occasionally but that's unusual. compression on a 3.0 should be around 150#.

same numbers i was thinking as far as 0% leak down if the guy doing the leak down cant read a Gage maybe he thinks its 0%

ed

[JFairman]

Most mechanics will put the car on the lift when looking things over on the bottom.
If he takes the lower valve covers off, there goes most of the engine oil so a complete ppi is going to cost you an oil change and valve cover gaskets, nylocks and sealing washers too.
How often is that really done for a ppi?

I know you could leave the car on the ground and jack one side up high so the oil goes over to one side and then you can take the opposite side lower cover off without oil going all over the place, and repeat for the other side...
I don't think most places are going to go to that much trouble and risk getting under the car like that for a ppi.

I know that doesn't help the situation... it's usually a ri$k buying an expensive to fix old car.

[jsmithcds]

Thanks for all the input fellas.
I am over it now and ready to move on except for the little bastard sitting on my shoulder. He may sit there for a bit yet.
Here is what I am thinking.......

How's this sound?


New rings
Valve job
valve springs
valve guides
race wear head studs all around
rebuild/repair intake manifolds
964 cams
J&E pistons
new seals all around
check the clutch and replace disc at a minimum
overall inspection to take care of hoses and the like

Loading the truck to send the car this week end.

anything else while in the shop?

[john walker's workshop]

steel lower studs. arp are overkill for a streeter. shouldn't need pistons unless the mileage is way up there. stock mahle P&Cs last a lot longer than J&Es. webcam 20/21 cams are nice in a 3.0.

[diverdan]

John:

Thanks for your input on steel verses ARP. Are you advising Dilivar on the top row instead of steel? Thank you.

Dan

[john walker's workshop]

24 steel studs with aluminum cases.