[TR] [EXTERNAL] - Re: '3a ignition update and next
terryrs at comcast.net
Tue Jul 31 14:47:54 MDT 2018
Oh, man, I ALMOST understood.
So bear with me a moment and help me understand piston liners. They have to be .003 proud all the way around. If they mismatch on any side by some margin, head gaskets will blow. I'd always guessed that was because the head is a flat surface crushing down on an unequal surface.
Fast-forward to manifolds. The clamp is being pressed against manifolds by a flat surface (a nut and washer). Wouldn't that mean that the clamp is going to stay equally horizontal to that surface, hence wouldn't the pressure against a lower surface (say, one of the manifolds)be different, same as for the piston liners?
Okay. Now I'm scaring myself....
> On July 31, 2018 at 9:44 AM Randall <tr3driver at ca.rr.com> wrote:
> > Each individual manifold clamp has the dual function
> > ofholding down both the iron and the aluminum manifolds. Over
> > 60 years of service, the softer intake can develop
> > divots--mine did. I'm not by no means never--as in not even
> > an also ran--expert on such things, but it would seem logical
> > that under such circumstances the stress on the clamp by the
> > nut cinching it down, would not be evenly applied to both
> > manifolds according to factory specs, regardless that the
> > mating head surfaces are still match grade. If a compressibl
> The hole in the clamp is larger than the stud, allowing the clamp to pivot
> against the nut and apply reasonably even pressure to both manifolds even if
> they are slightly different thicknesses.
> There is a limit of course, but I have never found it necessary to enlarge
> the hole for more clamping range; and I use stock equivalent gaskets.
> As mentioned, it is important that the surfaces be reasonably flat. It's
> not unusual to find exhaust manifolds that have warped, and cylinder heads
> that have a raised area around the stud holes. Both can be solved by hand,
> with dexterity, patience, and a fine tooth flat "machinist's" file.
> Always use new spring washers (aka split lock washers) as the heat often
> causes old ones to lose their spring. Check the nuts for tightness often,
> until you quit finding one that is a bit loose. I find that it also helps
> to use a heavy flat washer (aka setup washer) on the outermost two studs
> (where there is no clamp).
> -- Randall
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