I have this on my Vectra. One of the bolts has sheared holding the manifold on to the engine block....goes quiet after a while as the gaskets warm up. My mechanic advises to leave it as it common for others to shear while they are being loosened to get the manifold off...There after, like the original sheared bolt...they have to be drilled out....not worth the hassle or the expence..well not until the engine totally falls apart at least.
When I bought project Elite, it had a manifold blow, on the driver side bank. Unfortunately, one of the studs was snapped. More chance of pigs flying than getting a drill in there.. so decided it was a head-off job. Then decided, silly to do just one head - lets take both off and do a top end rebuild!
When I got the heads off.. there was 1 snapped stud on each bank already, and a further two on each head snapped on removal. So my mate and I had the joyful task of drilling out 6 studs, and then re-tapping the holes! To be honest, though, it was surprisingly easy, just time consuming.
Once manifolds refitted and torqued, they've not blown a bit.
Much to Mark's disgust when he saw it, we used some exhaust paste around the passenger side manifold - AFTER fitting and torquing the gasket whilst dry, I must add. On reflection, a bit un-necessary, and would make it a nightmare to remove in-situ now.. but it sure as heck doesn't blow
