Pulled head studs

[not_sure]

I see this problem posted all the time, is it safe to drive the car that way and how many people do it and for how long? Just curious...

[Leland Pate]

The problem I think is this.
Some people say it's ok to drive with one broken stud. That may be true but you run the risk of doing some serious damage to the cylinder head mating surface from it banging against the cylinder. If you catch it early enough you might be able to get away without having your heads machined (all three have to be machined the same amount).
I drove my car for another 4 months after discovering the broken stud. I was very carfull not to accelerate hard in an attempt to keep the head from flopping around. I would suggest not driving a car with a broken stud because of that plus the fact that it would only make sense that it would also increase the load on the remaining three studs and possibly cause them to fail prematurely as well.
I really didn't have a choice because at the time my 911 was my only car.

[john walker's workshop]

every time the cylinder fires, the head is lifted off it's sealing surface on the cylinder, exhaust passes thru the gap, and the head drops back onto the clyinder. both pieces are soft aluminum. serious irregularities form from all this pounding, requiring machine work to correct, or replacement of parts that are too far gone. the more it's driven, the more it will cost to fix.