Results of too much boost

[Geoff Daniels]

Completed the autopsy this evening on my 951 that was so nicley caught on film by Harlequin during it's last moment of life.

The good news is that it was just the head gasket and everything else looks really good. I have a picture shows what >20 lbs of boost can do to a 20 year old head gasket but it is bigger then the website will allow me to post. Any tricks for paotins pictures

New parts are on their way and with any luck it should be DE ready by Sunday.

Geoff

[Trak Ratt]

Completed the autopsy this evening on my 951 that was so nicley caught on film by Harlequin during it's last moment of life.

The good news is that it was just the head gasket and everything else looks really good. I have a picture shows what >20 lbs of boost can do to a 20 year old head gasket but it is bigger then the website will allow me to post. Any tricks for paotins pictures

New parts are on their way and with any luck it should be DE ready by Sunday.

Geoff Dial back the boost, try a 20 minute run... just once :p

[Alan Herod]

I observed that Geoff had the boost dialed way back, perhaps to less then stock levels; but, he failed to relay that the over boost was caused by failure of the overboost control (melted hose).

[Trak Ratt]

I observed that Geoff had the boost dialed way back, perhaps to less then stock levels; but, he failed to relay that the over boost was caused by failure of the overboost control (melted hose).No he said that during lunch, just couldn't resist!

[Geoff Daniels]

Your a tough man DR. One day I will get more then a few 20 minute runs in and get promoted to White. Then I will turn up the boost and see if I can with you. :)

[Trak Ratt]

Your a tough man DR. One day I will get more then a few 20 minute runs in and get promoted to White. Then I will turn up the boost and see if I can with you. :):shock: I was soooo wrong! Keep the boost on full now... don't miss a chance to have fun in blue... white is overrated and I already have hunt and scott to deal with

[APKhaos]

Hey Geoff,
A head gasket every now and then is worth it, right?
I had a cycling valve fail, so rigged a very simple bleed on the wastegate control line to keep running for the weekend. It was fairly peaky, but when it peaked to 20# the car just leapt up the track. Its addictive. Guess I might have had a bit too much fun with it. I installed a new cycling valve for our VIR race, but too much time at 20# took its toll. The head gasket blew on the cool down lap AFTER the checker. :D :D :D

Head gaskets are dead easy in our cars after you've done a couple.

[Trak Ratt]

Head gaskets are dead easy in our cars after you've done a couple.Then they're the only thing that is... well except for breaking :p

[Alan Herod]

Tony, did you do head studs every time you changed head gasket or did you install raceware the first time and never change them again?

What is the recommended technique for removing head studs?

[Geoff Daniels]

Tony, you are absolutely correct, a head gasket is a pretty easy fix. I could have had mine fixed in less then 4 hours if I had the parts sitting on my bench. This motor was a unmolested 20 year old motor so when the head came off I had some major corrosion on the top stud by the #1 cylinder. I am replacing the studs with raceware studs. Getting the old studs out is the only hard part of the repair.

I have deleted the CV valve and have a manual boost controller which was set at a conservative 13 lbs. When the vacuum line to the waste gate failed the turbo went to full boost which I am guessing was in the neighborhood of 25 + lbs of boost. It is a larger then stock turbo. It pulled like a banshee until the head gasket had enough, this only took a few seconds.

With raceware studs and a widefire gasket I may have to crank the boost up to about 16 lbs. Then I should be ready for DR, at least I can humiliate him on the straights. :)

[APKhaos]

Tony, did you do head studs every time you changed head gasket or did you install raceware the first time and never change them again?



The head studs in the 944 are around 4 inches long. Mine happen to be ARPs, but they were there when I got the car, and I've not changed them. Unlike 911 head studs, which are much longer, they are not a regular change item in the water pumpers. Head stud removal involves everything from simple clamping extractors [if you're lucky] to air arc excavation [if you're not].

With raceware studs and a widefire gasket I may have to crank the boost up to about 16 lbs.

The stock studs and gasket are more than adequate for 16psi. Racewear & widefire will give you a bigger margin, and are good up to around 20psi. Above that, things get complicated. The cylinders tend to 'walk' around on the head, which calls for o-ringing the head, and maybe a cometic gasket [some like 'em, some don't]. Above 20psi, all checks are bigger and all guarantees are void. :twisted:

[Geoff Daniels]

With a big sigh of relief I can report that all 10 head studs were successfully excised from the engine block. They really are a pain in the ass. I will now install my new raceware studs and sleep well at night knowing that I will not have to go through that again on this engine.

Hopefully I will have it running by tomorrow afternoon.