Re: k&n fipk killed my motor & S-Bolt?

From: Jeff Lee (
Date: Mon Jun 08 1998 - 09:32:37 EDT

I think that the S bolt arrangement is the best. Given the offset of the
bolt, it looks impossible for it to spin loose and fall into the TB
unless the whole air cleaner falls off. It doesn't even seem likely that
the offset bolt using the factory bracket would be able to fall out into
the TB, as the bolt hole in the bracket is centered over the ridge
between the bores - you have to remove the bracket to get the bolt out.
But... stranger things have happened...

As far as the S bolt breaking, did any of you guys use threaded rod?
When you were bending it, might you have bent it too far on the first
pass and had to adjust the bend for a perfect fit? The threaded rod
approach although easier is inherently weak, because the bends will
occur between threads where the rod diameter is thinner. Any back and
forth motion will stress the rod and the bend and cause fatigue failure.

My suggestion for the S bolt is to use a grade 2, 1/4" x 5 1/2" hex
bolt. This type of bolt has only 1" of threads at the end, with the rest
of the shank full diameter up to the bolt head. Make one of your bends
in the shank just above the threaded portion, and the other bend up the
shank at the appropriate location (see Sean's dimensions). Cut the bolt
head off to leave the correct amount of shank to receive threads, and
then cut just enough threads on the new end with 1/4" die. Dress with a
grinder, and you'll have a very strong S bolt - you'll rip up the top of
your air cleaner before you break this sucker.

Stay away from higher strength bolts, such as grades 5 and 8. Although
this may sound like it will produce a stronger S bolt, it won't. The
harder bolts are substantially more brittle and are not designed to be
bent. If they don't break immediately when you bend them, they will
likely break later while installed on your engine. :P

I guess the other good lesson to learn from the kilt motor story is...
always check the tightness of the air cleaner bolt whenever you pop the
hood. A one second task could save a bunch O money. ;)

98 rc v8 5spd 3.55sg flares fipk

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