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I am using an original Shelby intake on a 289 and was wondering why there are no rear water passages? Whats a good intake that does have the rear water passage for a midrange 2000 to 4000 rpm boost, i am running a mild cam, hyd lifters, headers and 4100 1.08 carb and MSD dist.
 

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The rear water passage is omitted from performance intakes to reduce the heat build up in the manifold. Lower intake temp = more power.
 

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No 289's had rear water cross overs in the manifolds.
Why do you feel that you need one?
 

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As far as I know, this is because the heads are not "side specific" and, thus, must have coolant passages on both ends so that, depending on which side they are installed, will have a coolant passage at the front. I, personally, can not see what advantage a rear coolant passage would offer as the coolant flows from the back to the front, not from side to side. Heck, the only reason there is a crossover in the front is to return the coolant back to the radiator through the water neck in the intake manifold (thermostat housing).
 

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I have seen on the net where somebody tapped both passages for fittings and used a length of stainless steel hose for a crossover. Quite a bit of work and expense, so he must of thought it was worth the trouble. I have no idea if he knew what he was doing or not though.
I have more than a few old FoMoCo intakes laying around the garage. None of them have the rear crossover. With their engineering degrees and work experience, I rather suspect the guys at Ford have a fair idea of what they are doing. They felt the rear passage was unneeded. Good enough for me.
Oh yeah, your intake says "Shelby" on it. Everybody knows that guy knows nothing about 289 performance parts. Better dump that nasty old manifold quick. ::
OR..
It ain't broke, don't fix it.
 

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engine coolant flows along a "path". radiator to pump, from pump down both sides of the block(front to rear) from block UP into the heads(at the back) and forward thru the heads to the intake manifold crossover then finally back to the radiator. a crossover at the back will serve no purpose whatsoever. just an FYI ::
 
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