DLS

And it looks like it has happened again

I raced against a lotus esperit v8 and when we pulled over i had some coolant that had come out from the coolant overflow hose

I only ran 17psi, i´m beginning to regret that i didn´t put in a audi engine instead........

Now is the question, why is it doing this?

Is it headlift?

Can i fix it with arp headstuds and cometic gasket or is it my ignition and fuel maps that needs to be adjusted?

Sometimes i wish that i had bought a link stand alone instead of the maf-kit in the first place

Adonay

Are you sure there is no air inside the cooling system you can refill water as many times as you want. If there is any air in there it will dump the water every now and then.

333pg333

Unfortunately it sounds all too familiar. As Corleone suggests, maybe it comes down to ign map? We figured it's headlift due to prolonged moments of boost while on the track. As much as you think you're going fast when you street race, it's only for very short bursts. On the track it's probably 60-70% at a guess. The loads are way harder on the motor than street driving.

Might be a combination of both timing and some mechanical changes such as 'O' ringing, or deckplates, or bigger headstuds torqued higher....the quest continues.....

gt37vgt

its the hottest spot in the hottest cylinder that starts the knock if there is an a big air pocket next to inlet port that part of the head will be hotter and that cylinder will knock . this is why Corleone "stem vents" or easy bleeds all 4 cylinders I Ive taken the concept a bit further and have a grove cut on the deck of the 3.0 siemesed bore and will drill small holes in the head gasket to eliminate anywhere i think an air bubble my stop..

Corleone

No, no headlift. Its hotspots in the cooling channels that boil and release air, the air is ackumulate and rise the pressure and then the cap open. When the cap open the pressure drops and the coolingliquid will boil even more at more spots and at lower temperature and then its nothing to do. This will come with the power/heat and its a poor Porsche head construction that is quilty.

Sorry to say but the only way to solve this is to remove or evacuate the air pockets.

Supernotch93

Corleone, could we use this as an example for why you vented each intake runner on your head? I thinking this is an excellent idea and will be doing the same.

DLS

But you did run 18-19psi on your old engine without trouble??
Why can´t i run 17psi, and it´s on the street.
all that run higher boost on the track, how is that possible?

fast951

This may not be the cause of the blown headgasket. It can be hardware (hed gasket, head studs, mating surfaces,...) or tuning related.

Back in post #268 you stated that your are using the Bosch HFM5 MAF. As far as i know, the MAF in use does not support high flow numbers.. Have you checked to make sure you are not maxing out the MAF (ie. hitting max signal output at low RPM)?

Corleone

Yes, something like that but the problem came with the heat. It was ok with shorter runs but if I WOT for 10 seconds the pressure increased.

Thom

Very interesting.
I think I was having the same issue as DLS when I ran 17psi.
I could see traces of dried up coolant at the end of the overflow hose but when I placed a recipient below I never got coolant to spill through again, but that was after I had lowered the boost to 15psi.
This is on the 3.0 engine, I never experienced this with the 2.5 though I continually ran it at 18psi.

DLS

I´m using a bosch 0 281 002 421
http://www.guzzimental.com/documents...%20Sensors.pdf

Measuring range: 15...1000 kg/h

is that high enough?

DLS

So you had problems with the 2,5l engine as well??

What can i do to fix it then, lower the boost or fix steam vents on all cylinders like you?

The car is soo much fun to drive when the boost is above 18 psi, it´s wild

333pg333

But what about our headgaskets that are getting ruined by what appears to be an abrasive movement? There is no sign of knock on the pistons either. It just looks like there is minor headlift and the cylinders are able to vibrate even to a very small amount, therefore 'rubbing' away at the headgasket and eventually breaking the seal.

DLS

What boost do you all run??

333pg333

At least the same as you.