Endless Unecessary or necessary replacments while there, questions

[ahh911]

Hello Guys,
Hope things are well, crazy stuff out there.
1981 911sc, ~100kMiles.

I'm starting to compile the final list for the top end rebuild and it's grown into a shopping list of questionable purchases. If you know, please chime in:


1. Spark plug wires and connectors all measure 1.1kOhm, +/-30 Ohms, even when wiggling. Don't replace, correct?
2. The head stud nuts and washers, pictures attached. All I've done is soak them in a rust remover chemical evapo-rust. Re-use the barrel nuts right? Washers, maybe?
3. Oil return tubes, pictures included. They seem far from rusting through. Replace?
4. Conrod bearing bolts, nuts? already apart the bearings all looked good, more $$$ wafting away. Replace.
5. Rocker arm screws, they all screwed out, but some with back and forth as the nut had been on so tight the nut must have distorted some upper threads, new screws for these?
6. Rocker arm shafts, any that show unusual wear?

I won't go on, because it's endless. What do you guys think?

The list of replacement parts must be in the hundreds and I'm fed up with replacing stuff that's not necessary. Huge list..... and the car was in good shape, that's the cruddy while your there theory... injectors, starter, alternator, air tubes, etc...

I may add more..., come to think of it, some of this seems wasteful as well.

Thanks,
Phil

[donbecker1234]

Hi Phil,

I'm not going as deep in as you.

I have a 79 930 engine that ran okay with some oil leaks but nothing major.

I did have at least one leaking fuel line, which lead to me just pulling the engine and transmission to get a better look. I'm simply removing everything down to the long block, and don't plan on pulling the cam towers, etc.

On my car, there isn't much in the way of service history. So I've been telling myself that replacing all the fuel lines, oil lines, etc etc is essentially establishing a baseline on the car.

One thing I think should be considered is whether or not you like doing the work, and/or whether or not you have the budget to just have a shop do everything.

Although I'd rather do something other than work on my motor, I have a higher budget for parts if I'm doing the labor myself.

[ahh911]

Thanks Don,
It's almost to the point where things are getting wasteful. Like those head stud nuts, in the old days no-one would think of replacing them, just re-use. I feel like I'm just throwing parts away that would otherwise see another 30 years. Especially without snow/salt.

[donbecker1234]

Originally Posted by ahh911

Thanks Don,
It's almost to the point where things are getting wasteful. Like those head stud nuts, in the old days no-one would think of replacing them, just re-use. I feel like I'm just throwing parts away that would otherwise see another 30 years. Especially without snow/salt.

Regarding reuse, I think the internet has a way of showing more and more bad things happening to engines. Sort of like people being more likely to review/comment in a negative way, and when something works right they are less likely to comment.

I think another thing that leads me to replace non-new parts is thinking about future troubleshooting, and the idea that "well I replaced that 3 months ago, it's likely not the issue" but that's not really a sure thing, and it seems in some cases the new parts aren't lasting as long as the original/old.

[ahh911]

For sure. I'm more of a, the starter is sitting there, it looks old, I'm not going to suffer to put another one in later. I just hope the new (rebuilt Bosch) one doesn't stick when warm, the one I have doesn't. Injectors same thing O-rings are shot anyway...(air boots, etc..), alternator needed brushes soon and bushings (sort of, barely) so replaced, engine hot air blower.. took that apart yesterday, ordering new brushes, bushing sleeves looks great, whew.. Every oil tube and gasket in sight, pressure sensor (old one worked fine, didn't bounce, but was 80 date code), temp switches in back, on and on..

I don't mind switching out all those things, it's the one's I know don't need replacing but I don't have the guts to re-use them. My Dad would have re-used half this stuff and it would still work 20 years later. Wimpy generation. The internet is great, but only if enough people comment on success and failures, as you've said.

[dannobee]

Judicious reuse of parts is acceptable. Since I worked at dealerships forever, I might have a somewhat better idea of what you can reuse (although asking some people on the internet, it's a wonder than many of the factory authorized things we did over the years even made it out of the driveway, much less lasting the life of the car!). When the factory would refuse to pay for something, we'd get the message loud and clear.

One way to look at many things is by asking yourself how hard is this to change in situ, or is this a safety item that might cause some kind of leak.

Rod bolts? Most definitely change. The cost of failure would be in the thousands. Oil return tubes? Easily changed in situ. Change the o-rings and call it good. O-rings on things like injectors? Change them, a leak could burn the car down. Consumables like gaskets? You really have no choice but to change. Starter or alternator? They were working before you took it apart, right? Clean up the outside if it makes you feel better and run them. Nuts and bolts? Unless there is a specific reason to change them or they are one-time-use, like teardown for broken head studs or rod bolts, just clean them up and run them.

[911pcars]

I don't think I've ever seen a steel nut fail except in a high load component (e.g. con rod). You're going to have to rely on your judgement or someone more experienced. Enlist a Porsche tech/machine shop who can inspect and advise. Inspection is about 1/3 of an engine rebuild. If you have the budget, sell your old stuff and replace. How do you feel about your crankshaft? Crack test it? Not being facetious. It's a relatively low cost inspection for high speed rotational parts and adds to the build confidence, but not altogether required.

Reminder. New parts can have a half life of 5, 50 or 150,000 miles and/or fail right out of the box. It all depends on fate, luck and sometimes a sharp eye. Sometimes price is an indication, but there's still expensive/overpriced crap and good stuff in the marketplace. The challenge is not to exceed the budget without compromising the build.

Sherwood

[ahh911]

agree with everything so far, what upsets me is the rod bearing check. I took them off to make sure they looked ok, and they did. No valve strikes on pistons, wrist pin bushings measure in spec, timing chain tensioners still plenty of headroom, 3.0SC has the larger rod bolts, so really I shouldn't have checked because all the signs said no trauma. I sure hope the new rod bolts are quality inspected. I'll definitely have the high power magnifying glass out again. Also the heads have been machined, I'll have to decide to lap or not as the exhaust valves to seat show 0.5 thousand gaps rough guess as light comes through but a 1 thousand/inch feeler gauge still mildly catches. (rotated several new valves on heads to make sure it wasn't the new valves, very repeatable).