Head studs on 1974 2.7L
 

Hi there,

Just picked up a 74' 911 with original head studs & 87k miles - otherwise appears to be in good shape & well maintained. I was given the advice from the P mechanic that inspected the car to time sert & replace head studs.

I have been doing a lot of research online & on this forum (thank you) and have learned some of the problem with the 2.7L magnesium cases was to do with the smog equipment required in 75' and later making the engines run too hot.

Does the 74' block that never had the thermal reactors installed suffer the same fate before 100K miles or has it a negative stigma attached to it because of the engines in 75'+ that ran hot failing?

Would you recommend doing the head studs (and ultimately all of the other engine work that comes along with it) as preventative maintenance, or wait for a head stud to break?

Thanks!

Brad

The head studs for that engine are steel and are not themselves paired with issues. The issue is occasionally the studs pull from the block due to the nature of magnesium, which is why when these mag cases are rebuilt they are always built with case savers for the head studs. Case savers give more meat for the stud to grab onto in the block. It's the later studs that have a bad rep for breaking. Don't tear into it unless it's giving you issues or if you simply want to rebuild it and do some upgrades is my motto. A '74 block is indeed a good starting point when compared to the '75 emission blocks, but I still don't write off '75 blocks if they measure up well and are in spec.

head studs
 

I am currently rebuilding a 75 2.7S engine. When disassembling, all of the head stud nuts were very loose...i could almost remove them by hand.......all steel studs, no thermal reactor exhaust.......

here's why the nuts were loose. Most of them had pulled enough to remove the mag case threads.....I.E. past due for timecerts....

http://forums.pelicanparts.com/uploa...1587484436.JPG

If i were you, I'd check the stud nuts, by re-torquing to spec.....if you can re-torque to spec...you are likely good to go and the engine may already be timecerted.....if you cannot re-torque to spec...it's time for timecerts.

I would not fix it if it isn't yet broken unless you have the urge to.

Just maintain reasonable engine and oil temperatures and keep track of the head studs when you're under the valve covers (i.e. valve adjustments, etc.). There's always a slippery slope waiting to be revealed when the goal is singular.

Sherwoood

Thanks for the responses guys!

So, a '75 isn't necessarily a boat anchor and can be saved using the timecerts?

Wellwood,
The head-stud pulling issue was prevalent among the engines with thermal reactors, especially in warm climates....but none of the mag cased engines are immune. Most 2.7 cases have been time-certed (or approved equivalent) by now....and that addresses the head-stud pulling problem. However, over time and once the engines are disassembled, the cases can warp and require additional work, like align-honing or align boring of the mains ,etc. to return them to spec. Basically, you need the case inspected to verify the work required......

The pic i posted earlier of the pulled stud(s) is one of the worst cases I've seen........I have another 2.7 I'm building for one of my projects that had no studs pulled and the case is in great shape.......

regards,
al

PS: the 2.7 is one of my favorite engines.......

Thanks for the insight.