yeh it aids to warm the inlet manifold when the car is cold. Although they are better at corroding them out and causing a mystery air leak!

its funny cos i actually had a look at the engine stamp and it seems to have been grinded off??? i never looked at it when i bought the car because i was just going to pull the engine out anyway

are all the droopy inlet manifolds off vanettes?

the vannette ive got doesnt have the droopy inlet or waterheating

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neither does mine actually, but it makes sense that they would have, to clear the seat.
post a pic of your vanette ;)

vannette photo is up

water heated ... for on cold days and also vapourising fuel a little better with the extra heat in the manifold 'heatbox'

did gx heads come with this

its not a head specific thing ... the GX setup does have water heating except that the water comes out of the head into the manifold dirctly, the exhaust and inlet manifold aren't connected. on the GX heads there is 3 or 4 (cant remember ??) that are cast into it that are located under the inlet ports ... theres pics on the site that show them

When Nissan moved away from exhaust 'hot spot' manifolds & made the inlets & exhaust manifolds separate, they included water heating of the intake instead.

This is not to perform some trick when the engine is cold, it is intended to keep the manifold heated ALL THE TIME so that any fuel that has not already been turned into a gas & is clinging to the intake wall is quickly evaporated & drawn into the cylinder to be burned.

As the smog laws bit deeper it was necessary to run progressively leaner mixtures in order to comply & this meant that every last droplet of fuel needs to be turned into gas in order for it to burn. [fuel in liquid form does not burn]

They found that the hot spot design of earlier years was not making the grade. For a stock vehicle that is used in ordinary ways, this is a great idea as it maximised driveability as well as economy while keeping nasty unburned hydrocarbons out it the exhaust output.

This basic water heated inlet manifold concept was first introduced with the 1200 GX when it was not practical to use any other method of providing heat to the twin carb manifold. In both single & twin carb engines, the coolant flows into the manifolds coolant pasages from holes under the inlet ports at the manifold face. These passages run underneath the inlet runners in the manifold, then to a common take out point at the front & is drawn into the water pump intake pipe at the front of the engine.

They're so amazingly clever those Datsun engineers.