Minimize head & cylinder damage from broken stud(s) by retarding timing?

[NEWFIE 69 911E]

Hi all,

Please see below quote from an old post:

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.

Very interesting

Does anyone else have experience with this? Thoughts from the Pelicans?

Thanks, and safe motoring

[Ronnie's.930]

That is just another example of doing something stupid and trying to talk yourself into believing that it is ok . . .

[Bob Kontak]

Scratch the "hard as normal". Just drive it like a wimp and save up for the re-fresh this fall. A couple of degrees retard can only lessen the severity of potential damage.

What is the ROW 1980 CR?

[Josh D]

8.6:1

[NEWFIE 69 911E]

Thanks for the replies - any other thoughts?

[Josh D]

There is some logic to the idea that retarding timing will reduce cylinder pressure. Whether or not it is enough to prevent further damage due to broken headstuds is doubtful at WOT. It would just make more sense to keep the car properly tuned and manage engine stress with your right foot. I know, not easy to do. Just keep an itemized cost of a rebuild where you can see it while driving and that might help!

[nicfranc]

Has anyone driven on a broken stud for any length of time ?
How about more than one broken stud ?

Obviously not a good idea but if you could make it through the driving season
you could then schedule a winter rebuild.

[manbridge 74]

Ultimately, here is there deal on vehicles approaching 30+ years old... try not to "limp" them around with band-aid fixes and wishful thinking. This is why you see so many "my 911 burned to the ground, I rear ended a guardrail type threads."

And believe me when I say I've fallen into this trap before with cars that are as fun to drive as the 911. The temptation to drive them in sub-optimal condition is very strong.

[Josh D]

Originally Posted by manbridge 74

I've fallen into this trap before with cars that are as fun to drive as the 911.

Ok, name one!

[manbridge 74]

... should have said cars that are almost and close as, fun to drive as the iconic 911.

Nearest guess would be ....... a modern sports car. That is how far ahead my 74 feels minus 915 trans.

[Tippy]

Retarding timing induces additional heat to the combustion process if too much.

[Steve@Rennsport]

Originally Posted by nicfranc

Has anyone driven on a broken stud for any length of time ?
How about more than one broken stud ?

Obviously not a good idea but if you could make it through the driving season
you could then schedule a winter rebuild.

I've seen the results of driving around with broken head studs for awhile and its not pretty.

In a nutshell, the heads and cylinder sealing surfaces beat each other up pretty badly and this means more machine work to repair. In some situations, everything is damaged beyond a reasonable repair since one needs to take too much metal off to restore the sealing surfaces and the result is excess compression and deck height problems.

My recommendations is always to stop driving it until the engine can be properly repaired as that's the least expensive solution in the long run.

[NEWFIE 69 911E]

Originally Posted by doverjxp

Just drive it like a wimp and save up for the re-fresh this fall.

Thanks for the replies,

My 1980 911SC has approximately 190K KILOMETERS (RoW model, purchased in Germany). Soon after I purchased it in Rhode Island and drove the car home to Newfoundland, I discovered one broken head stud. Going against "better judgement", I have driven, and thoroughly enjoyed, the car for the past 5 summers, driving approx 7K KM in total. I have been checking for oil leaks, and the tell-tale ping, ping on a constant basis, but the car continued to run perfectly.

Late last summer the engine starting to ping-ping under almost WOT, but only when hot. So, I stopped driving it, and planned to complete a top-end rebuild over the winter as a project with my eager and talented 17 year old son. Alas, life got in the way, and we did not get time to work on the car over the winter, and spring is (sort-of) here!!

I understand the damage that we will cause by continuing to drive the car, and am prepared to fly-cut the heads, so I am considering driving it, carefully, like a wimp for maybe 1K km over the summer, and start the rebuild with my son in the fall.

I am also prepared for, and appreciate, replies from those who think I am crazy, but that is how I am leaning.

So, call me crazy, I want to minimize the damage, and saw the old thread re retard timing to minimize damage, and would appreciate any additional thoughts on this. Thanks,

[mreid]

Almost every sc owner has driven with broken head studs. The difference is that once you see or hear symptoms you need to address them before minor wear becomes significant damage. I would fix the problem now. Replace the studs and rings while you're in there reseal the engine and you will drive for years with confidence.

[mpetry]

I once heard a similar argument about a rusty front pan (it's not that bad, no need to replace it, the forces aren't that great, etc etc). Guy came over to my house with his kid in the car and I took one look - I could see my shoe under the car when looking into the front compartment. It was held together by a spiderweb of rust and the grace of god. I shrudder to think what might have happened if it came loose (loss of control, head on into oncoming traffic) The guy sold the car instead of doing the fix.

Don't rationalize stuff like this - fix it! It will always cost more if you just "keep driving it".

/markp

[don gilbert]

this is what will happen. just more mach. work and more dollars.

[NEWFIE 69 911E]

Thank - good advice all - maybe I should transplant the well-running 2.0L from my somewhat rusty 69 911E into the 80 911SC whilst I rebuild the 3.0L from my SC?

At least that way I will have a 911 to drive this summer!!

[manbridge 74]

^^ Why not? The guys who raced their 911s in the 70s-80s could supposedly change out an engine/trans in 2hrs at the track.

I'd say if you don't hear the "playing card in the bicycle spokes noise" you could probably enjoy some light driving.

[NEWFIE 69 911E]

Originally Posted by manbridge 74

^^ Why not? The guys who raced their 911s in the 70s-80s could supposedly change out an engine/trans in 2hrs at the track.

I'd say if you don't hear the "playing card in the bicycle spokes noise" you could probably enjoy some light driving.

Thanks - I only hear the "ping-ping" playing-card-to-spoke noise on WOT when the engine is hot. According to the old message (that started this thread), the noise (and damage ?) can be minimized by retarding the timing a few degrees . Seems like a good idea to reduce damage for those of us who start to hear the noise but can't stop to rebuild, like when on a road-trip

This strategy assumes, of course, that no-noise = no damage . Comments?

[Ronnie's.930]

Originally Posted by NEWFIE 69 911E

Thanks - I only hear the "ping-ping" playing-card-to-spoke noise on WOT when the engine is hot. According to the old message (that started this thread), the noise (and damage ?) can be minimized by retarding the timing a few degrees . Seems like a good idea to reduce damage for those of us who start to hear the noise but can't stop to rebuild, like when on a road-trip

This strategy assumes, of course, that no-noise = no damage . Comments?

No offence meant, but this is not the case - nine times out of ten, when the engine is operated with a broken stud, you are going to find some damage to the cylinder/head mating surface regardless of what sounds you hear or what changes you make to the timing. Anyone that says differently, such as some that are advising that it is ok to drive, even moderately, with a known broken stud, are just plain wrong and allowing their "wishful thinking" to get the better of them.