What were they thinking (part 97.3 of infinity)

General Discussion
1

In the ongoing saga of “What were they thinking?” I had to scratch my head on a recent repair.

The torque specs called for 89 in/lbs on the valve cover bolts. Why such an oddball number?

Like using a round number of 90 in/lbs is suddenly going to result in the destruction of the bolt or hole by increasing it 1 in/lb? It can’t be that critical so what compels the engineer to specify something like that?

During another repair, I was loosening numerous fasteners that were the ubiquitous 10mm. Then, for whatever reason unknown to normal humans, there are two that are 13mm. Same bolt length, diameter, thread pitch and same type of clamping force so why change head size?

This seems to be a throwback to the olden days where there was a lot of mixed hardware. Then they discovered the benefits of using same sized and type of fasteners throughout. Maybe this was a geriatric engineer…?

2

Because you’re using an antiquated and outdated measuring system that few other people use. I mean you weren’t using a 3/8" socket on that bolt, right? You were using a 10mm.

Try 10 Nm for the torque spec. That’s the correct value, an easy round number to remember. :grinning:

3

BOTH values are correct, as per your typical factory service manual

Since you mentioned valve cover bolts, it’s almost certainly M6x1.0 we’re talking about

10Nm and 89in-lbs will both be listed