Postby DewCatTea-Bob » Thu Feb 21, 2013 2:14 am
" these are factory sizes "
____ Thanks for the great/detailed help Joe ! _ (As I-myself was not very-much caring to bother looking-up a parts-book to find all the stock fastener-lengths.)
" a lot of them can and should be upgraded to longer bolts (especially the top two valve cover bolts on each valve cover, i use 20mm long instead of 16) "
____ I also prefer to use 20mm-lengths at those four upper-locations but, there's then a chance of their thread-shafts becoming bottomed-out against the rocker-pins before the cover gets fully tighten-down...
To prevent that from happening, not only do ya need to employ the stock extra-thick valve-cover gaskets, (rather than mere sealer-paste),, ya also should include aluminum-washers* under THOSE four locations !
(* The four screw-hole locations above the rocker-pins are a source of oil-leakage [which the Allen-heads alone can't seal against], so the factory finally addressed that issue [on the later w-c.models], by adding suitably sized aluminum-washers for those four locations [only].)
Otherwise, 18mm-lengths are all the longer that will properly fit (in those four spots),
and 18mm-screws will fit ALL 17 cyl.head threaded-holes without any thread-tapping ! - (However WITH thread-tapping, all the other 13 fastener-holes will accept 25mm-lengths.)
____ I've added a pic showing the three main types of flat-nose thread-taps, and only the one shown at the far-right is suitable as a "blind-hole tap", as IT is the only type which will FULLY thread a hole all the way down to it's very-bottom (as needed) !
__ The four holes with a rocker-pin (unfortunately) located at their bottoms, are the only holes which won't benefit from such a thread-tap, (as THOSE holes are already threaded as far inward as possible).
Dukaddy-DUKEs,
-Bob
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PLEASE NOTE... If this-post is not-yet signed-off with '-Bob', then I'm still in the process of completing it,, and if not also included with 'DCT' near bottom as well, then I may edit this post's wording at a later time. - Dct.Bob