3.0sc - split case or not?

[Flat6pac]

Much of the times the broken stud causes the head to warp and the sealing surfaces need to be flycut.
Bruce

[KR8]

Thanks Bruce for the information. Got everything back from Ted all look good except for #5. It had some marks on the top of the cylinder. Here is the before pix.




I forgot to take an after pix, before I wrapped them up in a box for storage. I’ll get that out soon. A few marks but really not that bad and all ready to go.




I started on the bottom row head studs with the Snap-On tool, really easy on the first six. No need to add heat or any power tools. #4 first stud and #5 first stud didn’t move so I passed. #6 first stud (the reason I went down this road broken came off with a pliers – simple. Went back to other two that didn’t come off and two weekends later they are off. Minus a couple tanks of gas – a whole lot of heat and couple new extraction tools. I’ve read so many threads about problem studs and what everyone has to go through - Now I know all about head studs.





I’ll start installing the 12 new steal studs in a couple weeks – holidays and travel are eating up my time.

Report back later, with pixs.

[Kemo]

im in the same boat...broken head studs on my 78. 4 of them, to be exact. I also had a cylinder-head gasket disentigrate which kinda messed up the head but can be fixed at the machinist. I also found a broken piston,hairline- between the rings. Fortunately, I have MAHLE cylinders that are still in spec so im waiting on a new set of JE pistons to go along with the head work. thanks for posting, this looks oh-so-familiar

[KR8]

Once I recieved my parts back from Ted it really showed more damage than I thought I had on the top of #5 piston. Question - should I clean (grind down) this up or just leave it?

[MBAtarga]

strange - looks like impressions of bolt threads on the piston - any ideas on what caused it?

[KR8]

No, I bought this engine last year off of a local P-Car guy. Yes, it must have been a small bolt and there is no sign of it anywhere now.

[Walt Fricke]

KR8

I'd take a feeler gauge to the top ring on that damaged piston. See if the bolt dented things enough to cause a pinched spot above the ring. If it did not, you could clean up the damage with a file or something similar. Your goal would be to remove any sharp edges and generally smooth things out, rather than to try to recreate an unbroken surface like the rest of the top of the piston. And do the same with the #5 cylinder head. I think I can see pecker marks in the combustion chamber in your photos.

If you worry about such things, you could rebalance your pistons. Buy a digital postal scale at an office supply store - maybe $30 or so, which will weigh 2.2 kg or so at a 1 gram resolution. Then use a die grinder to make them all match the one which is lightest.

An alternative would be to find a good used piston for the '78-9 motors. Should be plenty around, but be careful about Nikasil vs Alusil. You would want to try to get one in the same weight class, or one a bit heavier so you can balance it down.

I once had the machine screws which held Weber air horns shake loose and get swallowed. Did this kind of superficial damage. One of three pistons had to be replaced, the other two have worked fine for years thereafter (Mahle 10.3/1 race 90mms, hard to come by and expensive). One had ring groove damage. But surface irregularities soon get carboned over.

I would carefully inspect the #5 cylinder for scratches, though.

[KR8]

Walt,

Thanks for the info, and I'll check the weight and evaluate from there. The only damage on the cylinder wall is the small marks in the pix above.

[Walt Fricke]

Right - I later saw those scratch marks.

You might post that picture on the 911 engine rebuilding forum and see if any of the professional engine builders there think they are important. Me, for a budget rebuild, I'd be inclined to let them be if they don't stick out. Your finger nail ought to tell. But I can't say I have used something like that. My disaster didn't affect the cylinders.

Used but in spec cylinders can be found, but it is always nice to have things in pairs.

[KR8]

Even the damaged piston weighs (392g with rings) the same as the rest. Maybe I could grind down the #5 just a small bit, weigh it again and if there is a big difference I could just take a little of the rest to match?

[Walt Fricke]

Consulting a spec book I find Porsche saying the maximum weight difference should be no more than 6 grams for 2.7 and 3.0 liter pistons. But you could lighten the #6 a shade to match (after weighing a smoothed off #5) and call it very good. This isn't an 8,000 rpm engine anyway, is it?

[KR8]

Hey Walt,

My conversation was completely wrong, the pistons all weigh between 561.31g - 564.15g , these are with the rings. They are all within the 6g's of each other. You are correct this will not be running 8000 rpm just stock.