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My 1978 3.0 L head stud replacement thread

 
Old 09-08-2011, 10:31 AM
  #61  
whalebird
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Awesome thread Brett. The pictures are worth the price of membership alone. I've been following without the time to chime in...and you have good advice already. For the o-rings, i always apply a thin coat of the Dow 111(or whatever it is) silicone paste for assembly. As for the heads, By all means have them checked out. At bare minimum, hand lap the valves yourself...it's easy and kinda fun. Air cooled motors ask a lot of their valve train in terms of cooling and the guides should certainly be in check if you are "in there". In years past, I have sent several sets of heads to Andial and they always do a great job.
I also recommend a good look at the pistons and rings. If you need to rering...do it. I just did the DIY alusil reconditioning on my 924S motor(944) with the Sunnen AN-30 paste and it was so easy I would have no problem suggesting any novice do this at home. I'll send you my AN-30 paste if you need some...there is plenty left. I went with Goetze (OEM) rings that I fitted to each cylinder and was satisfied with their fitments. I know this is a highly debated subject in the 911 community, but It was a no brainer for me when it was over with. I have 800 miles on my motor now and it is tight; I know it will be fine. Keep it up and the picture are superb.
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Old 09-08-2011, 11:09 AM
  #62  
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Originally Posted by Brett San Diego View Post
...

Same to you Alan, Do you have a broken one? And I thought I read Dilavar doesn't weld well. I'll have to look into that. (Well assuming the studs are Dilavar. Need to get out the magnet.)
No, I don't have any broken studs, but I can't resist the temptation to replace them while doing the rest of the motor. My studs on the bottom (exhaust side) are coated in a black finish and I think those are Dilavar (still need to the do the magnet test myself). The intake side studs look to be bare steel and have light corrosion in places.
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Old 09-08-2011, 02:15 PM
  #63  
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If I may go out on a limb...I do know that Porsche 'upgraded' the head-stud nuts for the 993. As I understood it (in factory training) that the shape was changed for better airflow(?). If you have the studs, I would suggest the associated hardware be used/replaced. This may be worth a little research on your part as I don't know the compatability on older cars. Just a thought.
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Old 09-08-2011, 02:40 PM
  #64  
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Whalebird: I have purchased new head stud barrel nuts and washers. I was not aware of different hardware for the 993 studs. I'll look into that. Thanks for your comments.

Brett
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Old 09-08-2011, 02:52 PM
  #65  
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A quick google seach revealed that yes, the 993 is different; sort of mushroom shaped. If they are usable in a 3.0 remains a question. I would think you are fine with what you have if nothing else, again I'm thinking out loud.
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Old 09-11-2011, 11:14 PM
  #66  
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I've said that I thought that my engine is on its second round of stud replacements based upon the remaining shine on the exhaust side studs versus the general dullness of the finish on the intake side studs. That may not be the case. I have finally realized the intake side studs are steel (magnetic) whereas the exhaust side studs are dilavar (non-magnetic). The difference in appearance may not be due to age but just the materials used. It's possible that the exhaust side studs are still the original dilavar studs. Upon re-reading the literature on head studs, the steel intake side and dilavar exhaust side arrangement was in use during this period of production. Nevertheless, someone has been inside this engine before as noted by the slipshod use of fasteners, the different #5 cylinder head, and the broken valve tappet (elephant foot) that I found a few years ago in the sump.

I have now removed the pistons and cylinders. Nothing to report about the process, just did what Wayne Dempsey says in his 911 engine rebuild book. The cylinders slid out easily. Then pistons were removed from the rods.

Looks like I have nikasil cylinders. "Mahle" is cast into the base of the cylinders, which means it's a good chance these are nikasil. Checking with a magnet confirmed that the cylinder walls are magnetic. Alusil is non-magnetic

Pic of "Mahle."


As far as being able to ID the cylinders without removal... The "Mahle" is cast in the side between the cylinders. You can see well enough between the cylinders once the cooling guide tinware is removed to make out the letters. The two cylinders with oil grime are #s 5 and 6, more fallout from the breather hose oil leak.

All the cylinder walls look pretty similar. Cross hatching pattern still very evident with some visible score marks straight up and down. Most of these score marks cannot be felt with the pointed tip of a pick tool or can just barely, barely be felt. On #5 however, there is one particular score mark that is much deeper and more palpable with the pick. Could be bad news for this cylinder... I don't know. I've never done this before...

The score mark on #5


The pistons were pretty much identical in general appearance.



Most showed a little light wear patch on the skirts just below the rings. At least, I think it's a "light" wear patch.


But, piston #5 had two little flaws on the very edge of the crown. They almost look like casting flaws, but maybe it's some kind of damage. Again, I don't know due to my inexperience, but it may be recommended not to reuse this piston. These flaws do not line up with the score mark pictured above on the wall of the #5 cylinder.



All the wrist pin bushings looked exactly like this one. Some silver colorations on the crank side of the bushing. Again, I don't know what this means. The wrist pins themselves looked flawless. You can also see the broken stud.



Here's a pic into the cylinder spigot showing the piston squirter.



And, here's another view of the broken stud on the exhaust side of #3.



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Last edited by Brett San Diego; 09-12-2011 at 01:46 PM.
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Old 09-12-2011, 02:11 AM
  #67  
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I read that one of the changes to the later cars (3.2 Carreras and maybe later SCs - not sure on that) was that Porsche started coating the Dilavar studs with a black "paint" of some type, which matches what I see on my engine. This may partly explain why broken studs do not seem to be quite as common on Carreras as SCs.

I will soon have my pistons and cylinders out this week too. It will be interesting to see what similarities and differences may exist.

Great pictures as always!
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Old 09-12-2011, 09:11 AM
  #68  
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Outstanding pics . I wil be interested to hear what some of the experienced engine builders have to say about some of the pics. Steve W hasnt been around for a bit but i am sure he would have some great insight.
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Old 09-12-2011, 01:40 PM
  #69  
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Originally Posted by 500_19B View Post
I read that one of the changes to the later cars (3.2 Carreras and maybe later SCs - not sure on that) was that Porsche started coating the Dilavar studs with a black "paint" of some type, which matches what I see on my engine. This may partly explain why broken studs do not seem to be quite as common on Carreras as SCs.
Yeah, in my last picture, you can see the corrosion on the other #3 exhaust side stud. So, anything done to stop the beginning of that corrosion is a good thing. The head studs all the way through the 993 Turbo were still made of dilavar but are coated with a black coating, and there is never an issue with those breaking. The coating must make the difference.

Are your intake side studs steel or dilavar?

Brett
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Old 09-12-2011, 01:44 PM
  #70  
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Originally Posted by theiceman View Post
Outstanding pics . I wil be interested to hear what some of the experienced engine builders have to say about some of the pics.
Me too. I'll probably cross post a few of these pics on the pelicanparts engine building forum to get some more exposure to highly experienced folks.

Brett
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Old 09-12-2011, 03:17 PM
  #71  
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Originally Posted by Brett San Diego View Post
Yeah, in my last picture, you can see the corrosion on the other #3 exhaust side stud. So, anything done to stop the beginning of that corrosion is a good thing. The head studs all the way through the 993 Turbo were still made of dilavar but are coated with a black coating, and there is never an issue with those breaking. The coating must make the difference.

Are your intake side studs steel or dilavar?

Brett
Hi Brett, having done the magnet test, I can confirm that my intake studs are steel, and exhaust studs are Dilavar. I am still debating what to use for the rebuild. All-steel OEM (intake and exhaust) seem to be a well-proven option for normal builds. However, the 993 studs you are using have a very good rep and of course there are the Supertecs, Raceware and ARP options.

Right now I am leaning towards OEM steel as I think they should be appropriate for my application and "affordable"!!!
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Old 09-15-2011, 01:02 AM
  #72  
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All rocker arms and the camshafts have been removed from the cam housings. Things are not looking good.

The rocker arm cam following surfaces weren't so bad. They all kind of looked like this. Only this one showed this bit of rust.



Trouble spotted when I got to the #2 intake rocker. Yes, those are all pretty deep gouges in the rocker shaft.



The bushing wasn't much better. Here's a couple of views of rows of pits. These are two separate rows going across the bushing in slightly different locations.




The other shafts and bushings weren't anything like that bad, but there may have been loose tolerances. I think they should all be rebuilt.

The cams came out next. They just pull right out once you've removed the rocker arms. This was the first one I pulled. Uh, oh. One tiny pit in one lobe. That's one tiny pit too many. Looks like I'm headed for a cam regrind.



This was the second cam out. Even worse. Two lobes had significant pitting. This pic is the worse one. Definitely heading for a regrind.



I'm concerned about the bearing surfaces of the cam housings, too. I don't think the visible circumferential lines are an issue, but there are a lot of little pits in the surfaces. They are small but palpable with the tip of a pick tool, and they are numerous. I'm not so sure these cam housings should be reused. More expert opinion will be necessary. Here are a couple of pics of the bearing surfaces.




All this is obviously concerning. I was not intending to split the case, but the wear evident on some of the top end bearing surfaces makes me wonder what the bottom end looks like. Maybe I better have a look. There is also some extra goop smeared around a couple of case fasteners on the bottom side of the case, possibly an attempt to stop a case leak... so, splitting the case and getting a look at the bottom end is probably the best path forward at this point.

I thought this was a low mileage car, 44,000 miles showing when purchased from the second owner in 2004. I didn't have many records, but I did have a couple of shop receipts from the year 2000 from the original owner showing 39,xxx miles. What I'm seeing makes me wonder. As I mentioned before when I found the different cylinder head, this 911 did see the track with the original owner as evidenced by the eyebolts installed for harnesses, and presumably, there was a major failure leading to some major engine work to the extent of putting in a different cylinder head. Perhaps this wear I'm seeing stems from metal bits circulating through the oil system from this failure. I don't know, but I'm thinking I had better get eyes on the main bearings and crank journals.

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Old 09-15-2011, 01:19 AM
  #73  
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Local to me:

http://www.webcamshafts.com/

check out page 52
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Old 09-15-2011, 05:01 AM
  #74  
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Yep, I'll be paying Web Cam a visit in the future. As costs continue to mount for this head stud replacement, it may be longer in the future than I wanted...

Brett
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Old 09-15-2011, 09:21 AM
  #75  
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I'd definitely split the case to see what's going on.

Webcams is a good company, I'm sure, but there is another gentleman, John Dougherty at Dougherty Racing Cams, who does a lot of Porsche cam work. Yes, he does stock specs too. Much more reasonable in cost than webcam, IMO. He can also rebush/surface the rockers.

PS to Doug: See???
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