Ping!

[surflvr911sc]

I have a ping under load I can't quite track down. Could this be timing, clogged injector or carbon build-up causing high compression? The valves were just adjusted so I know their OK and the ping was there before that was done. I know Pings are bad, what would the most likely cause be?

[MotoSook]

Have you tried a higher octane gas?

[scedmonds]

I just posted this response under the "Octane" thread -- a timing problem was the source of my ping. My wrench said it was slightly advanced, and it's solved now.

Cheers!

C.

[john walker's workshop]

it's a pinging for sure? another board member thought his engine was pinging, and it turned out he had a broken head stud on his '82. poor fuel, too hot, too high compression ratio, timing too far advanced, too lean, etc. cause pinging.

[Doug Zielke]

That "board member" is I. After fooling around with various motors for over 35 years, I would have bet the farm I was hearing detonation from the motor. Nope. Just a common broken head stud. The similarity of the two noises (detonation/broken stud) was amazing.

Before you go mad adjusting your timing, buying av-gas, replacing your injectors, etc., pull the lower valve covers and check the head studs.

(And JW, the Blue Bomber thanks you for calling her an '82. She's really a year older. Blush. Blush.)

[surflvr911sc]

OK I admit it! I have a broken head stud. I'm still not sure that’s what it is. My wrench (Porsche only >30yrs) said my compression is really good, and it is running good. (Not counting the ping, I haven't talk to him about that yet.) He said He thinks I should drive it the way it is until I start to lose compression or I feel like spending the money to replace my head studs. I think I can feel it when I'm accelerating hard. Right when I hear a slight ping, I feel a slight hesitation, then gone. What do you guys think? Try not to beat me up too hard.

[speeder]

My '82 has one broken headstud, does the exact same thing. Only under load, and more pronounced when engine hot. Otherwise runs like the proverbial "scalded banshee", smooth as spun-silk, and EXCELLENT compression across the board. Starting to wonder if there is an un-rebuilt 81-83 SC ANYWHERE w/o one broken headstud.

[surflvr911sc]

So you think the sound is just a head leak then? Do you think my mechanics advice is sound? I do trust him when it comes to my car, Like I said Porsche only >30yrs. He hasn't steered me wrong yet. He said as long has there is good compression and the other studs look good, and I don't break another one, it will be fine. Are there any long-term effects I should consider? Possible damage? I don't mind it if the consensus is that's OK but I want to be sure. Thanks for all your guys' input.

[john walker's workshop]

personally, i don't think it's a good idea to put too many miles on it with a broken stud, although there are others on the board who think that the cam tower holds the row of heads tight enough so there's not a problem if only one stud is broken. if you're hearing the exhaust escaping between the head and cylinder, under acceleration, the explosion in the cylinder is obviously lifting the head off the cylinder it's supposed to be clamped against, right? i can see not worrying too much if there's no noise and the stud is on one of the center cylinders (2 and 5), which do have the support of the cam tower, but the outer ones don't have as much support. an aluminum head continuously beating on an aluminum cylinder will cause some damage to the sealing surfaces eventually, requiring ALL the heads be flycut to restore the surface, not to mention what to do about the top surface of the affected cylinder(s).

[targa80]

About six years ago I took my car to a porsche only garage for a complete tune up and oil tube replacement (they leaked badly. The engine had 85K on the odometer. They found two broken studs one on each cylinder bank of of the engine. I was told that the comression was still solid and not to worry until I have a second broken stud on the same bank or a loss of compression. Since I do enjoy driving my car but only have short sessions of agressive driving style (getting on the highway or passing a slow poke and that enviting curved country road). So, I took the advice and ran the car for several more years until I had a major oil leak from the oil temp sensor on the top of the engine. The car now had 96K on the odometer. I puled the motor and did the rebuild myself. I did find a second stud broken but never did notice any difference in performance. Between parts, machine shop work and special tools I did not own and had to buy I spent close to $7K on the work. I did all of the major updates to my 3.0 and used Pelican parts as a supplier. It was the first Porsche engine I had rebuilt and I learned a lot. The engine runs great and the odometer now has 118K .

When to repair the broken head studs is up to the individual and how much risk your willing to take. If you are a real aggressive driver and push your engine to the red line then do it now and don't wait. But if your like me It wouldn't hurt to postpone therepair until the time is rigt for you. By the way I still have my moments of aggressive behavior.

Targa80

[Neunelf]

I'm surprised Superman hasn't posted on this one yet. Do a search- he just finished up an abbreviated rebuild to fix this very problem, with the goal of doing just what was needed without spending a lot extra. I can't remember what he ended up doing in detail vs. what wasn't done, and there was debate on the merits of that, but his reasons were well thought out and are something to think about.

Super- do you want to weigh in here? Drag yourself away from that Gov't stuff in Olympia- this is important!

Good Luck- Roy

[speeder]

Targa80, I need to do the same to my SC sometime in near future. Incidentally, I replaced my oil-press. switch already, $14 and one hour. That was the impetus for rebuild?

I guess my question for you, (and anyone else), is what cost $7000?? I planned on doing work myself, re-using P/C's, new lower studs,(~$120), engine seal kit,($100?), carrera tensioners and new ramps, (~$400), possibly a valve job, but probably not this time around since I have 100% compression in all cylinders, (115k miles), miscellaneous other repairs, minor rebuild on 915, ($? for parts only), maybe all new SS exhaust, ($1100). But of course trans and exhaust are separate from rebuild expense.

Where does all of the money go on these 3.0 rebuilds, when all vital parts, (case, P/Cs, bottom-end, etc.) are fine??? I'm about to *****-can my SC before having carrera $$ in it w/ still SC resale.

[Doug Zielke]

I'm one of the ones that will drive my SC with the 1 broken head stud....carefully, at least, until the fall when it's top-end rebuild time. (Can't miss the SCWDP Round-Up, and few other events this summer!)

Last Saturday, I had breakfast with John Walker and he warned me about the possible consequences (head damage). I would not doubt this knowing his vast experience.

But here's a tip for those who are planning to tempt fate for just a few more summer miles.....

I found that if I *retarded* the ignition timing a few degrees, I could drive the car as hard as normal. This, *without* inducing the dreadful "pinging" noise of the head slapping the cylinder.

My mechanic suggested what I was doing in reality, was taking a bit of combustion pressure off the cylinders. It works, and although the retarded timing takes some snap out of the SC's acceleration, I can easily live with that for a little while.

[speeder]

Doug, I understand what you are saying, but I would think that retarding the ignition of an air-cooled engine, especially in the summer, is really tempting fate since it will make it run hot. This is not some theory, it is fact. I would think that a better plan would be to leave it in perfect tune, (timing, mixture, etc.), and just avoid WOT under load. This is my game-plan, and believe me, you can still have PLENTY of fun w/ the car. Good luck.

[Doug Zielke]

I was waiting for this........Conventional wisdom.... ( as Superman often says here) etc.,etc., etc.

Of course, I monitored engine temps carefully after retarding the timing 5 degrees. There is *no* apparent increase in engine temps. I know how the gauge on my car responds to various driving conditions, there was no change, so I have no concerns about overheating. Nor does my pro-mechanic.

[NEWFIE 69 911E]

Originally Posted by Doug Zielke

I'm one of the ones that will drive my SC with the 1 broken head stud....carefully, at least, until the fall when it's top-end rebuild time. (Can't miss the SCWDP Round-Up, and few other events this summer!)

Last Saturday, I had breakfast with John Walker and he warned me about the possible consequences (head damage). I would not doubt this knowing his vast experience.

But here's a tip for those who are planning to tempt fate for just a few more summer miles.....

I found that if I *retarded* the ignition timing a few degrees, I could drive the car as hard as normal. This, *without* inducing the dreadful "pinging" noise of the head slapping the cylinder.

My mechanic suggested what I was doing in reality, was taking a bit of combustion pressure off the cylinders. It works, and although the retarded timing takes some snap out of the SC's acceleration, I can easily live with that for a little while.

See above - I found this message in an old thread that suggests that one may be able to minimize physical damage from driving with broken studs by simply retarding the timing to stop the dreaded "pinging noise" of the head slapping the cylinder

Has anyone else tried this?

Thanks,