I'm making a set of custom manifolds for my 1500.
To get the baseline dimensions for making the flanges,
I have measured several cylinder heads and manifolds.
I was surprised to find that there is a lot of
variation in the heads, with the alignment of the
intake ports with respect to the dowel pins, as much
as 1/8". This even varies from side to side on the
same head!
FWIW, the 4 ZS manifolds ( 3 small port, 1 large port)
were all very consistent, within 1/32". But with small
port manifolds, it doesn't matter anyway.
This variation can cause problems when fitting the
manifold gasket, sometimes the port is shrouded by the
edge of the gasket. And of course, a manifold with
large ports will not align perfectly either.
FWIW, I have a Pierce Weber DGV manifold, and the
holes for the dowel pins are about 3/32" oversize, I
guess to allow the manifold to be aligned without
removing the dowel pins.
If you are concerned with max performance, you must
check the alignement, and hand fit as required.
If your manifold is short and straight, you can just
remove the carbs, and peer into the ports to align the
manifolds. Otherwise, try this method:
1) Fit the manifold gasket to the head, check the
alignment. If the ports and roll pins align perfectly,
great! Otherwise, reverse the gasket to see if it's a
better fit. Trim the gasket around the ports with a
file or grinder if there is blockage. Use a marker to
indicate which face goes out (or in).
2) Use the gasket from above to check the alignment of
the manifold ports (using the proper face). If the all
aligns perfectly, great! Otherwise, place horizontal
and vertical alignment marks on the outside of the
manifold and on the gasket.
3) If the roll pins do not align perfectly, remove
them. Fit the gasket ( mind the face marking ), and
then fit the manifold(s). Fit the keepers and lock
washers, then tighten the nuts just tight enough to
hold the manifold in place, but loose enough to allow
it to be 'tapped' into alignment. Using the marks from
step 2), align the manifold(s) to the gasket. Tighten
the nuts to spec.
BTW, in the comp manual for the MK I and II, Kastner
suggested drilling small holes and using pins to get
the manifolds perfectly aligned each time. Maybe that
would work here too.
Carter
--- Davies William-qswi646
<William.M.Davies@motorola.com> wrote:
> > -----Original Message-----
> > From: T. .R. Dafforn [mailto:td214@cam.ac.uk]
> >
> > Just about to instal a new manifold to head gasket
> on a 1500
> > to sort out
> > an vacuum leak..
> > Anyone any helpful suggestions?
> > ie. Is it worth using any gasket compound?
> > Cheers
>
> Hi Tim,
> There should be no need for any gasket sealant
> here.
>
> > PS I am fitting a twin weber manifold, 2 piece,
> one for the front car,
> > and one for the back...
> > I am finding aligning them a bit hard, but I
> noticed a small
> > hole in the
> > face of the head, in between the two inlet ports,
> that matches one on
> > the inlet manifolds, what are these for, and can
> they be used to help
> > alignment?
>
> There should be a roll-pin in that hole,
> specifically for aligning the
> manifold,
> Cheers,
> Bill.
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