For people who have installed an intake manifold, do you always replace the bolts?

The manual says to replace the bolts anytime the intake manifold is removed. I thought that sounded silly, but then a bolt snapped at relatively low torque when I put the intake manifold back on. The bolts thread into the block itself, rather than mount on studs like the exhaust manifold and the torque is way lower for the intake (18.9) than for the exhaust (69 if I remember correctly).

That begs the question; Are the intake manifold bolts the equivalent of a fuse and meant to break before you can hurt your block? If that is the case, are they all suspect and should be replaced since they have already been torqued twice going on and off, and therefore may be weakened and prone to failure?

 

I have reused them for years......head bolts and studs are a different matter....

If they are torqued properly they tend to be OK...but if they are over tightened then they can fail on re-use

The thing to watch for is the bolt that acts differently than the norm. If the other 6 bolts take 2 revolutions to get to torque....and you get one that takes more...and the torque is low and doesn't rise properly....stop before it breaks....

 

clean the threads and use anti-seize to prevent water/corrosion from creeping in

 

If the manual says to replace them, they are torque to yield bolts and should not be re-used. That being said, I have never had an issue with intake manifold bolts. If they have excessive corrosion I replace them.