Looks identical to what I found when I pulled my old high mile engine. In my case I am convinced it was due to age and mileage which resulted in the hardening of the gaskets and loosening of the IH bolts. That engine was burning considerable oil as a result. In this case it may simply be the result of reuse of the IH gaskets when the previous engine work was done, which I believe was the case. Generally, once gaskets are compressed they never again have the same sealing properties if used multiple times. Dom has done considerable data logging on this engine. Had there been a manifold/crankcase pressure issue it should have shown itself in the MAP sensor readings, which, as I understand, was not the case.
After researching my issue and now this one I am of the opinion that this condition is much more common than we think. Several factors come into play. Loose IH bolts is a known issue. Age, mileage and the resultant heat cycles harden the gaskets and loosen the bolts. The design, with crankcase oil vapor galleys, coolant passages and intake runners in close proximity, with only a thin gasket to seal, is not ideal. Generally, IH gaskets are not high on the list when “top end” work is done. IH’s are not generally removed unless more major work is done. Even then no one pays attention to the IH gaskets.
In this case I would simply replace the gaskets, reassemble and (blue) loctite the IH bolts, then monitor crankcase/manifold pressures.
H
