KuHL 951

Sorry to hear about the head Roger. I'm curious if you recall seeing this when you pulled the head? That chunk would be hard to miss If the head was done by a good shop familiar with Porsche they should never have machined the head and called you before doing the work. From the looks of the fresh ceramic edges with no carbon marks I suspect this might have happened during the rebuild. If you do get another used head I would try and get the shop to do it again for parts only.

Tom M'Guinn

+1

special tool

They blasted your head.
No way it was like that before.
Is that a head modded by Andial at all??

Andial951

I dont think Andial did any modification to the head. I didnt notice the chipping in the port but then I never thought to look in there so I cant say if it was or wasnt chipped. The shop I used specializes only in Porsche (mostly 911 of course) and they have been around for a long time. Im reluctant to think the shop did it because I did have a previous turbo failure which another shop could not figure out how it happened only that the impeller was all chewed up.....so this leads me to believe that the ceramic chipped and got into the turbo. Its been over 2 years now since that happened and maybe about 8,000 miles and my current turbo is still good.

Sounds like everyone thinks I should get a new head but whats to say the ceeramic in that head wont come loose and damage my turbo? I guess there is never any guarantee.

Andial951

I thought it was the block that gets o-ringed not the head?

special tool

You can o-ring either the block, or the head, or both.

You CANNOT use that head again - it is junk.
It is not a matter of our opinion, unfortunately.

KuHL 951

Rest assured that if you use that head again 'as is' it will grenade your turbo as exhaust gases lift the edge of the remaining ceramic lining and send it home to roost at the turbine wheel. You said the last turbo failed on the impellor side which would be a nut or something ingested from the cold side. And yes, you have no gauranty it won't happen again with any head but your chances are much better. I'll try not to be so diplomatic in my appraisal of the machine shop this time; that large ceramic chunk in the pic has either fallen out, broken off, or been blasted off after the head was pulled. If you had 8K miles on that head it would not be white on the fractured cross-sectional surfaces. I've followed your car many times and you run rich under boost like most of us with 951's. Whatever toasted your last turbo was not the chunk of ceramic lining in the photo.

Also, looks they shaved that head quite a bit, there are no witness marks left or maybe I can't see them in the pics.

Andial951

Steve,

I think I didnt understand what you were trying to say in your previous post. I now see why you say the shop probably did it. But wouldnt there not be any carbon marks since he cleaned the whole thing? Is there absolute proof from lookikng at the head that the shop did it? If so I will go back to the guy and confront him on it but if it cant be proven I dont have much to stand on.

BTW - what are witness marks? Maybe they arent showing up in the pic but I can check the head tonight.....not that I think it matters anymore since this head is unusable now.

EDIT: I should make it clear that the head (if its original....no way for me to know for sure....i think) has 70,000 miles on it but its been about 8,000 since the last turbo died is what I was trying to say.

hosrom_951

Dave,
I was under the impression that both 8v NA and turbo heads are exactly the same casts, thus ports, with the exception that the turbo had the ceramic liners and hardware (valves + springs). I did not know that the NA head would require a lot of work to outflow a turbo head, unless you are referring to a non stock turbo head?

As for grinding the ceramic off, yes it is a waste of time, that is what i meant.

KuHL 951

Roger, There is a cast depression in the head near cylinder #2. When this is no longer visible you have reached 'at least' or 'exceeded' minimum deck height for the head and it should be measured to be sure it was not cut too far. It does raise your compression ratio somewhat which can be critical for a 951. There is a lot of debate about just how much can safely be cut on the turbo head without going to a thicker head gasket or changing piston top profiles; but I'll leave that to the experts.

EDIT:I just looked again and saw that your mark is still showing. This monitor at work sucks!

Witness Mark:

944CS

if it flew off from bead blasting, it was probably on its way off....bead blasting shouldn't take the liner off unless it was already starting to come off, in which case they did you a favor!

Andial951

Interesting point

a4944

I would recommend a new head. The exact same thing happened to me. I kept the old head and another chunk of ceramic liner fell off after about a year of just sitting in the garage.

Mark

TurboTim

Exactly.This should have been caught before the work was done.If you remove all the ceramic in the ports you end up with a head that has way to large of a port and you will hurt performance.The N/A heads have larger ports then the 951 head but the ports are still smaller then a 951 head without the ceramic liners.

George D

I would call the folks that did that work and ask why in the world they would send you this head back or even do any work on it. It's too bad that stuff like this happens.

Lart is offering you a really good deal on a head, especially when he won't take your $100 bucks if it's not in good shape.

George