I would check on the torque required to get that bolt into its working
range. If it is over about 60 pounds, I would use a lower strength bolt that
can be torqued into its working range at 65 pounds or less. The cast iron
holes will not stand all that much in the way of torque. Its kind of a fine
thread unlike good old American engine blocks with big diameter course
threads.
Real SAE grade 5 bolts can be bent sharply over 90 degrees without
failing. Grade 8 bolts, while capable of a higher ultimate loading (tensile)
seldom make it to 90 degrees without failing. They are much better in double
shear than the grade 5 but this is not it. My driver built up quite a store of
data on this subject while going through a half million dollars worth of
bodywork. Even with grade 5 or whatever that is in metric, torqued into their
working range, you could pick the plane up and shake it for 100 years by the
reduction unit and no fastener failures would occur.
Whenever we had a Cosworth apart we would change the rod bolts. They were
pricey but the owner wanted new bolts each time. I suspect that he went past
the red line every time he got into the car. The Cosworth rep came to Mid Ohio
once and found the owner. He wanted to know what we were doing to the bolts
that we needed so many. The rods were designed around the bolts. Deep enough
to get enough threads to get the bolt into its working range. Then center to
center distance and so on. He pointed out that they could tear the big end off
of the rod without failing the cap or the bolts. So if the rod cap was still
on the rod, it was fine. So we quit changing rod bolts. They had dimples on
each end and you torque them with a special dial indicator rig in place, until
they stretch .0035" and that was it. Not by torque. By stretch. We never lost
a Cosworth engine.
The bolt choice is limited by the cast iron holes. Perhaps studs for some
of the application.
Lynn E. Hanover
In a message dated 5/7/2008 10:42:50 AM Pacific Daylight Time,
echristley@nc.rr.com writes:
Where can I find extra long, high grade metric bolts that aren't
specialty order items?
What other options do I have for securely
bolting a plate to the back of
the engine with 6"
spacer?