Here's another question

[Tommy P]

This is really the continuation of a topic i posted some weeks ago under the subject:

1982 911 3.0L SC Sport - Number 3 cyl problem

Despite being advised that it may be possible to replace the valve springs on this cylinder with the engine in place, I decided to remove the engine for a number of reasons:
One was because it would be easier to do this particular job (I could see what I was doing). Plus I suspect the valve is bent because I couldn't move it by either pulling or pushing it. It still won't move now that I can get a better grip on it with the engine out.
This is the basis of my question, I'm guessing that the valve should move freely in it's guide and if it dosen't then it's probably bent. Am I correct.
Tom

[Wayne 962]

That would be a good guess. Assuming that the piston isn't up against the valve on the other side, it should move freely in the guide...

-Wayne

[Tommy P]

so here is the results of my tear down. Looks like I got away with damage to the No. 3 piston, but the valve is bent.
As you can see the valve isn't seating and the top right of the piston was only 'grazed' judging by the small amount of scouring visible.
At 127,000miles I'm now considering a full rebuild. My thinking is that, with the engine out and at this stage I might as well go for it.
It will take some time because of finances, but at least when the motor goes back in, it won't need to come out again for some time (fingers crossed).
I'm looking at going for Waynes 'Top engine picks' High Performance 3.0L. The gearbox need work too - so wish me luck - it's the firt time I've tackled a Porsche rebuild and I've never done any work on gearboxes before!.
I'll be needing some guidance from you guy's out there.
So be patient with me.
Cheers

[WERK I]

Tom,
What is the deal with piston within the red area. Is that a camera lense distortion?

[Tommy P]

Dave
must admit, I noticed that earlier, just after my posting, dosen't look good though. Hope it is a distortion. So I need to check it out. Will do that tomorrow and report back.
Perhaps another case of the novice not seeing, which is something I've become aware of - rather like the therapist and the client - we can only see whats apparent when something has been brought to our notice - the experienced eye!.

[Doug Zielke]

Bad news on the engine, Tom, but your excellent shots have earned their place in .....Doug's Mechanical Mayhem Files.

BTW: The MM Files are growing slowly but steadily. One day I hope to post them all on a website, for those who can't resist viewing a fine selection of metallic carnage.

[Tommy P]

Here's another couple of shots of the same piston, looks like it was a camera distortion - I'm glad to say.
Doug I've included another 2 Pic of the broken valve spring and rocker arm, just in case you can use them in your MM compilation.
Cheers

[Tommy P]

And one of the other part of Rocker arm.

[Doug Zielke]

Excellent work, Tom!
In the future, a legion of shameless devotees of destruction will thank you!
(And good luck with the rebuild.)

[Tyson Schmidt]

I don't think it's just camera distortion. In the second set of pics, you can still see some evidence of burning of the piston crown. This time it's at the bottom of the piston, since the pic was taken from the other side. You definitely need to pull this piston and have a better look.

[Tommy P]

Tyson
I'll look again, but I don't think it really matters at this stage. I've virtually made my mind up to do a full re-build, although some enlightenment wouldn't go amiss on your observations as a Porsche technician. Please explain burning of the piston crown?.
I'm currently trying to find suppliers and prices of 3.2 pistons and barrells for a conversion to 3.2 - anyone have info on this?
Cheers
Tom

[Tyson Schmidt]

Well, sounds like it doesn't matter then anyway. That's good. Upgrades always help alleviate the pain of the rebuild, since your getting more than what you had in the end.

The pistons burn, generally, on the exhaust (bottom) side of the piston and closest to the cylinder wall. But it can happen anywhere there is a hot spot due to detonation, leanness, overboost, lack of cooling, etc. A burned or bent valve can cause this hot spot, like in your case.

[Tommy P]

Thanks for that Tyson.

[kstylianos]

Tommy,

Nice troubleshooting and pics. Don't feel bad, I had the same outer valve spring broken on my 82 SC. Apparently, this is not uncommon for the 82 vintage.

BTW: I was told I'd probably have a broken spring before I even found it.

[pete911]

The "distortion" looks to me like a puddle of oil. I believe the picture is upside down.

Pete

[Tommy P]

Charlie,
I don't feel bad - it's just the way it is and to a certain extent (apart from the finacial implications) I'm looking forward to the experience of a rebuild. It will be an interesting learning experience, from which I can only gain, despite whatever pitfalls might prevail (you gotta be an opotomist to survive).
Pete,
I agree with you, when I returned to inspect the piston, I looked at how the oil puddle may have affected the photo (there's no substitute for being there), and could see how this may effect interpretation. However this does not represent any disrespect for Tysons input re - piston burn.
I do wonder though, about piston burn and weather this could occur after the spring had broken and the intake valve became bent, finishing in the closed position (which it was), possibly pushed there by the piston hitting it. possible consequence to this would be that, running at high revs (on track) the fuel mix (if any got to No. 3 cyl) would run lean???.
I don't know - I'm just guessing>
So here are a few more images of No's. 2 and 1 valve and cyls for comparison - just in case anyone is interested or can make some form of analysis.
Thanks for the responses by the way.
Cheers


Cyl No 1 valves



Cyl No. 2 valves



Intake and exh No. 1



Intake and exhs No. 2



Cyl 3-2-1



More of cyl 3-2-1

Some of the images may not be too clear for analysis, however make of them what you will. I'm just a novice so am unable to comment, therefore I,m at your mercy.
Once again, thanks for the imput and I hope some of the image's may be helpful to others on the site.
Cheers

[WERK I]

Tom,
Interesting pics, indeed. I don't think it was from a lean mixture, but from inadequate cooling across the cylinder 3. Check out the cooling fins when you get a chance. They maybe clogged with crud. It looks like the engine had a serious oil leak on #3 for some time.

[pete911]

Here is a pic of one of my heads and piston from an "incident" last year. I beleive a valve spring broke causing valve float. The piston then wacked the valve and eventually broke it off. This happened on the track at about 6900 rpm on a 3.2 motor. I put a used head and piston in it and had it running 5 days later. Ran great.

[Wayne 962]

The 3.0 to 3.2 pistons are about $3500 right now, if you can find them in stock anywhere. I think that there is one or two sets in the entire country right now...

-Wayne

[Tyson Schmidt]

Tommy, that could definitely be just a puddle of oil in that pic. Digital pictures can be extremely deceptive. That's how so much garbage gets sold on E-bay!