dlr944

Can you name the cause of this head gasket failure:

Specs:
Wide Fire Headgasket <5k (yr 2005)
SIII Vitesse Kit
Rebuit head by Peformance Developments <5k (yr 2005)
Runs 12.5:1 on WOT (dyno)
Factory studs

The fire ring, on the #4 cylinder head gasket, looks compressed but the water jacket edge is bludged?

Appreciate your thoughts on the culript?

thanks

Andial951

DAM!! That looks almost exactly like mine.........

hosrom_951

What is the age on that head gasket?

dlr944

The headgasket was changed in mid-2005. Not that old.

lart951

12.5:1 IMHO is way too lean, what you got there is the result of detonation, what boost level are you running? I personally like to run 11:7 - 12:1 at 18psi and 11:3-11:7 @ 21psi.

KuHL 951

Did you reuse the existing head studs?

dlr944

Yes, I re-used the factory studs and marked the tops to ensure they did not turn when tighting the head down.

hosrom_951

I saw 12.5-12.7 on factory cars.

Anything under 12.0 is rich, i even saw 13.1 on boost (3,000-3,300rpms) for the sake of hotter exhaust gases, effecing in reduced spool, then a rich 12.0 in mid range for torque and then a solid 12.5 till redline for power.

At least, that is the way i like it.

Absolutetly NOTHING wrong with factory studs.

Ian Carr

Thats why your head gasket went. porsche head studs suck after retorqueing them... ask me how i know

dlr944

Lot's of reasons why a headgasket can give... but it seems like the general consensus is the factory studs are re-usable.

The other interesting point to make is the #4 cylinder's water passage is damaged in many of the 951 headgasket cases?

KuHL 951

Personally I wouldn't use the OE studs twice on a Turbo. They are designed to stretch once only and shouldn't be used again. You might get away with it on a NA, but not a 951. Is there any chance that the HG had blown before making this one the 3rd time they were torqued? You just can't get the same clamping pressure to prevent head lift under boost unless you use studs like ARP or Raceware designed for reuse. Needless to say, buy new studs for the repairs. You also might look into the Lindsey Racing steam vent kit to prevent that hot spot on #4.

A.Wayne

That head gasket shows detonation damage ,typical for the no .4 cylinder..

stonger headstuds would have had the fire ring being damaged also , as the head would not have lifted enough to produce the damage behind the fire ring ..

dlr944

Any thoughts on why the #4 cylinder is the short fuse? Why is this typical...?

Thanks!

lart951

I have heard different reasons of why the #4 cyl fails, many said head desing, anothers claim air bubble is trapped in the back of the head and ultimately some think that it's a flaw in certain series of blocks. I blew 3 head gaskets months apart each on my 1st engine in my current 951, in the last blown headgasket I replaced the WF HG with the cometic MLS and in less than a month I had broken a ring thus damaging my block beyond repair. I never ran more than 17psi in my previous setup. I strongly believe that my block was flawed, Chris White a well known builder among listers said once that he believed that certain blocks might have been flawed by factory by a certain factor that remain a mistery until today, in another words certain blocks are cursed.

To put my previous setup into contrast I use 21psi daily for the last 3 years, I have ran up to 23psi and my a/f ratio has gone as high as 13:1 for a second but I also used 10-20% xylene depending upon boost level. But I have a different block and head also.

Keithr726

Ouch that sucks. Another project to add to my list. 120k and I think its got the stock HG. Will be interesting to see how it holds up once my car is boosting properly.