[TR] [EXTERNAL] - Re: '3a ignition update and next

Randall tr3driver at ca.rr.com
Tue Jul 31 18:14:44 MDT 2018

The key point is that the manifold clamps can pivot, while the head can't. The flat bottom of the nut does affect the pivot to some extent, but not much. The cylinder head OTOH is limited by the cylinder block right next to the liners.
-- Randall

On 31 July 2018 16:47:54 GMT-04:00, TERRY SMITH <terryrs at comcast.net> wrote:
>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
>> 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
>> the hole for more clamping range; and I use stock equivalent gaskets.
>> As mentioned, it is important that the surfaces be reasonably flat. 
>> not unusual to find exhaust manifolds that have warped, and cylinder
>> that have a raised area around the stud holes.  Both can be solved by
>> with dexterity, patience, and a fine tooth flat "machinist's" file.
>> Always use new spring washers (aka split lock washers) as the heat
>> causes old ones to lose their spring.  Check the nuts for tightness
>> until you quit finding one that is a bit loose.  I find that it also
>> to use a heavy flat washer (aka setup washer) on the outermost two
>> (where there is no clamp).
>> -- Randall  
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