I know someone that has been running 18 psi on a standard head gasket for 20 years, just saying...Spencan wrote: Fri Oct 24, 2025 11:51 am I installed that same HG in May 2024 and so far so good. I have gone as high as 19 psi of boost.
Long road, but we're here
I’m only repeating what was shared with me and along with my experience and education it tracks.
944 Turbos that turn up the boost have been plagued with head gasket issues and there has been many attempts at overcoming it.
One path was going to aftermarket head studs made from hardened steel, like the common ARP variation. Unfortunately those are a fix that actually make the situation worse instead of better.
The OEM steel studs are designed to work with the aluminum block and aluminum cylinder head. As the aluminum block and aluminum head heat up they expand considerably. With the OEM studs designed to work with that, they stretch enough so that the expansion of the two aluminum components is within the compression tolerance of the OEM head gasket.
However, the ARP hardened steel studs have a much higher tensile strength than OEM so given the same load they will not stretch as much as the OEM studs. Since they don’t stretch as much, then with the expansion of block and head, the compression is actually higher on the head gasket which ends up permanently over compressing it passed its ability to maintain the seal and thus being “blown”.
There have been builds with ARP studs blowing head gasket after head gasket and then after switching back to OEM studs never blew again.
It all depends of course. Other things can contribute like a staggering high back pressure to boost ratio or a compromised cooling system.
I do really hope your build holds true but those aftermarket hardened head studs will hurt rather than help.
944 Turbos that turn up the boost have been plagued with head gasket issues and there has been many attempts at overcoming it.
One path was going to aftermarket head studs made from hardened steel, like the common ARP variation. Unfortunately those are a fix that actually make the situation worse instead of better.
The OEM steel studs are designed to work with the aluminum block and aluminum cylinder head. As the aluminum block and aluminum head heat up they expand considerably. With the OEM studs designed to work with that, they stretch enough so that the expansion of the two aluminum components is within the compression tolerance of the OEM head gasket.
However, the ARP hardened steel studs have a much higher tensile strength than OEM so given the same load they will not stretch as much as the OEM studs. Since they don’t stretch as much, then with the expansion of block and head, the compression is actually higher on the head gasket which ends up permanently over compressing it passed its ability to maintain the seal and thus being “blown”.
There have been builds with ARP studs blowing head gasket after head gasket and then after switching back to OEM studs never blew again.
It all depends of course. Other things can contribute like a staggering high back pressure to boost ratio or a compromised cooling system.
I do really hope your build holds true but those aftermarket hardened head studs will hurt rather than help.