[DeTomaso] Manifold crossover function question?

[MikeLDrew at aol.com]

In a message dated 1/12/09 21 10 10, rimov at charter.net writes:


> Ok, I realize I am becoming quite fixated on this, but to what end does the
> manifold cross over achieve other than being used for heating air around the
> choke tubes so the old fashion chokes would lean out the fuel mixture once
> the engine was at optimal temperature?
> 
> I hope this doesn't keep me up all night contemplating.
> 
> 

Don't worry, it won't. :>)


Although coincidentally the stock choke is actuated by a mechanism which is 
inserted into this cavity, that is its secondary function.

The principal purpose for the exhaust crossover is to provide heat to the 
underside of the intake manifold.  There is a huge pressure drop as fuel is drawn 
through the venturies of the carburetor and then expands into the intake 
plenum.  This brings with it a huge temperature drop, and fuel fails to atomize 
properly.  This is particularly significant on engines driven in cold weather on 
the street.

Race engines don't bother because they are normally running wide-open, and 
are typically very hot.  But a street motor running at part throttle in cold 
conditions can exhibit stumbling etc. if the crossover isn't used.

Don't take my word for it though. :>)

http://cars.rasoenterprises.com/Carbs-IntakeHeat.htm

Mike




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