Re: Carb for my T'all

[jlandry@domain.elided (John A. Landry)]

As the little green aliens inserted a searing hot probe into the sternum of
cookiedan@domain.elided (Daniel Nees), a blood curdling scream was heard...

>You need to buy a adapter plate for
>either the speadbore manifold AND the squarebore manifold so it doesn't
>matter which you pickup. 

Ben and Dan,

While you can use either a spread or square-bore manifold with the Edelbrock /
Carter / Weber carb, you only need an adapter for the spread-bore manifold.  

There is one important thing to remember about these carbs... While the
Edelbrock is laid out on the Holley square-bore pattern, the rear bores are
larger than the primaries.  If you attempt to bolt an Edelbrock directly to
the IH square-bore manifold, it possible that the throttle plates in the
secondaries could stick open when they rotate into the smaller secondary
manifold bores.  Credit goes to Owen Minor for pointing this out to me when I
was shopping for a new four-barrel carb way back when.  Don't fret though,
there are several ways to avoid problems with this.

But first I need to mention that no matter which style manifold you use, and
Edelbrock style carb needs to be insulated from direct contact with the intake
manifold.  The exhaust crossover inside the intake manifold really heats it
up.  If the carb is simply bolted directly to the intake manifold (using a
typical thin fiber gasket), the fuel inside the float bowls can boil.  This
can cause all sorts of drivability and starting problems.  Edelbrock sells a
phenolic insulating spacer that fits between the carb and manifold to help
block the heat, but this is not an adapter... just an insulator.  There are
several other types of heat insulating gaskets sold by various manufacturers.
Any good speed shop or well stocked auto parts store will have these.  I use
one that consists of a stack of fiber gaskets and aluminum sheets.

In order to get around the potential secondary throttle plate sticking
problem, all you need do is install one of these heat insulating gaskets I
just mentioned.  This raises the carb up off the manifold enough so the
throttle plate swings clear of the manifold bore.  This solves the problem but
isn't the *best* proper way to fix it.  What you're left with is a larger
carburetor throttle bore stepping down to a smaller intake manifold bore under
the heat insulating gasket.  This little ledge acts to restrict air flow.
When speaking of air flow through the carb, heads and exhaust manifold... if
you have to change size, you can go from small to large but are never supposed
to go from large down to small.  Luckily this only happens with the secondary
throttle bores which normally aren't used very often.

The best way is to take the intake manifold to a machine shop and have them
bore out the secondary throttle bores to match the carb.

Another less than perfect alternative is to take a Dremmel tool and grind out
small relief areas on the upper sides of the secondary throttle bores to give
the throttle plates clearance for free movement.  This doesn't solve the size
step down problem and isn't needed if you use a heat insulating gasket...
which you really should do anyway.

As far as adapting the Edelbrock to a spread-bore manifold, as long as you use
the Edelbrock adapter, you will not have a problem.  If you grab any old
adapter off an auto parts store shelf, you *could* have problems depending on
it's design.  Stick with the Edelbrock part and you'll be fine.

Look for a used manifold in local wrecking yards or the easy way is to read
the Binder Bulletin classified ads (www.binderbulletin.org).  I see them for
sale all the time.

Good luck,

John L.
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