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

Randall tr3driver at ca.rr.com
Tue Jul 31 07:44:45 MDT 2018

> 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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