Stan has pointed out to me that as far as he knows no one currently makes a
header with the correct 5/8" flange for the Roadster. If this is the case, then
the best you can currently do is get one with the thickest flange possible, and
that has the tabs already welded on. Ask your supplier to have the flange gasket
surface checked and ground flat if necessary, then have them ceramic coat it for
you (helps keep the header running cooler and leads to less warpage problems).
I thought I remembered that someone was making headers with the correct flange
thickness, maybe I talked with Don Potter about this, in which case they would
be special order, expensive, and slow to arrive, but probably the best headers
available. I ran into this same issue with the MGBs back when I made parts for
them, and I started having my own headers made with the correct 5/8" flange (hmm
sound familiar?:-). When I talked about this to MGB owners and vendors they all
told me I was nuts, wasn't needed, etc. But as soon as I started selling mine,
lots of vendors changed to full thickness flanges. Maybe what's needed is to
pressure one vendor into getting their headers made the right way (header
manufacturers will almost always be willing to do special runs if a vendor
orders a minimum quantity, and flange thickness is not a big deal for them since
all they have to do is use different sheet stock). I am pretty sure once one
vendor offers it, the rest will follow. BTW headers are one of the biggest pain
in the a__ products a vendor can carry. There are SOOOOO many manufacturing
problems with them it is scary. On L series motors I have had to go through a
half dozen or more headers sometimes to find one that would actually seal
reliably, especially on the L6s. I gave Les the $5 lesson on this last year with
one particular Z engine I built for him.
Marc Sayer wrote:
>
> No! (Well okay, it might work for a few folks, for a while, but it is a bad
> "solution") You do not want to arbitrarily mess with the compressibility and
> compressed thickness of gaskets. In fact this is generally one of the worst
> cheap fixes for this problem. Gasket design is based on science and you can't
> really just mess with the gaskets like this most of the time. The proper
> solution for a bunch of reasons (including a tendency to warp the flange) is
>to
> buy headers made with the correct thickness flange. Any other solution
> (including gaskets, tabs welded onto the header flange, and stepped washers)
> will only lead to problems. You *might* be able to address a problem where the
> intake manifold flange was thinner with one of these approaches, as the intake
> manifold does not tend to warp, but with a header this is a major waste of
>time.
> Yes a car maker could perhaps design a stepped or two-part gasket that would
> work, maybe. But an individual does not have the resources to do the R&D for
> this, *and* the issue of header flange warpage is still unresolved with this
> approach. In order of preference the solutions to this problem are;
>
> 1-get a header with the right thickness flange
> 2-use stepped washers (because this way at least the header flange is the same
> thickness throughout)
> 3-weld tabs onto the flange (welding on the tabs will warp the flange and the
> flange must be surfaced *after* welding, plus the varied effective thickness
>of
> the flange will cause warpage problems)
> 4-use stepped gaskets (NOT recommended)
>
> Spray on Copper Coat or just plain silver hi-temp paint (the aluminum pigment
>in
> the paint acts as a gasket dressing) work well.
>
> Paul Bauman wrote:
> >
> > Gary:
> >
> > Funny you should mention this. We stopped at an offroad shop that advertised
> > K&N filters and while showing the owner the beast, he mentioned that Jeeps
> > had the same problem with intake/header thickness. He let me see a manifold
> > gasket from chrysler designed to help solve the problem. It was a standard
> > flat manifold gasket that came with a set of smaller gaskets that fit on the
> > thinner manifold areas to help exqualize things. I was thinking of
> > 'sacrificing' a gasket or two to see if this fix would help on my car!
> >
> > Paul Bauman
> > Westminister, CA
> > 67 1600
> >
> > -----Original Message-----
> > From: owner-datsun-roadsters@autox.team.net
> > [mailto:owner-datsun-roadsters@autox.team.net]On Behalf Of Geegc@aol.com
> > Sent: Sunday, February 03, 2002 8:22 AM
> > To: datsun-roadsters@autox.team.net
> > Subject: Header thickness
> >
> > The exhaust header I just bought from one of our vendors is slightly thinner
> > than the intake manifold. I am wondering if I should grind down the washers
> > to create even pressure, or if its not necessary?
> >
> > Also, any recommendation for manifold gasket sealant? I have some copper hi
> > temp spray stuff I was going to use.
--
Marc Sayer
82 280ZXT
71 510 2.5 Trans Am vintage racer
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