Kelvin, thanks for the information.  I suspect the stock GM intake is
dual plane, mine appears to have the "two sets of intake tracts"?  A
single plane intake manifold would have one large intake tract that
serves all four barrels of the carburetor?
Larry Hoy, Denver, CO USA
1969 MGB Roadster (one half of a V8)
1987 Jaguar XJ6 Vanden Plas
It's not how fast you go, it's how fast you go fast.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On Thu, 26 Feb 1998 09:19:53 -0800 Kelvin Dodd <kdodd@West.net> writes:
>Larry A Hoy wrote:
>
>> get a question I have answered.  Can anyone tell me the difference
>> between a dual plane and a single plane intake manifold?  I have no 
>clue.
>
>Larry:
>       The dual plane manifold has two sets of intake tracts sandwiched
>one on top of the other.  The smaller bore tract connects to the primary
>side of the carb.  The larger bore connects to the secondary.  When 
>running under light load, only the primary of the carb. is operating.  
>
>The intake tract being a small diameter keeps the intake charge flowing 
>at high speed which helps distribution and keeps the fuel atomised.  In 
>theory, the smaller intake tract will increase low load drivability.  
>The combined bore of the prim. and sec. tracts can in theory be larger 
>allowing more flow at the top end whilst retaining drivability at the 
>low end.  One drawback is that the maximum bore is restricted by the 
>metal between the two tracts, but on our small bore engines this is not 
>a  problem.  
>       So in a nutshell.  Low end drivability and economy requires a 
>small carb. with small intake tracts to maintain high speed intake flow.
> High end power requires a big carb. with intake tracts matched to the
>bore size to allow the maximum flow the engine can pump.  The dual plane
>manifold was designed to combine these features.
>
>       Hope this answers your question.   Kelvin.
>
>
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