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Discussion Starter · #1 ·
'68 396, all stock. I'm just putting engine back together, and am about to install intake. the gaskets I have block off the entire coolant passage around the exhaust crossover. the crossover itself is open. I am running elec choke, and it will never see cold weather. want to leave it open. the butterfly after ex. manifold is wired open. anyway my concern is that the intake has a coolant passage under the carb location, under the exhaust crossover. I haven't been able to find a gasket that will allow coolant flow through there. is it supposed to be blocked off? it's a "hot slot" style manifold if that matters. those slots are blocked by pipe plugs. anybody know the correct gaskets I need?
 

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Discussion Starter · #2 ·
sorry, just realized the passages in head don't go anywhere. so then, anybody know what the purpose of these passages were for?
 

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The exhaust crossover is drilled into one of the exhaust ports in the head.
 

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There is no coolant running thru or under the exhaust crossover. Since you have the pipe plugs in the intake and an electric choke,I would either use the restrictors that come with the gaskets or block off the crossover. Blocking it off helps keep the intake cooler.
 

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sorry, just realized the passages in head don't go anywhere. so then, anybody know what the purpose of these passages were for?
I dont know for sure but always figured they were there to give a little bit of extra air cooling to the crossover area in the head.
 

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They helped with cold weather starting/running via choke spring expansion that was heated by the exhaust crossover.
 

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In cold weather with the exhaust flapper valve closed ( R.S.) A lot of the right side exhaust goes through the intake manifold, The exhaust passing through the manifold will heat up the CHOKE ASSMB. mounted on the intake manifold.
The spring starts to turn and the butterfly opens up, NOW the black smoke and rough running engine starts to smooth out. Blip the pedal once, Then it comes off the high idle ramp, GEE, Now it looks like a gas engine and not a Duramax ! :nerd: As always,---- I love it when a plan comes together !
Bob
 
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