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we are running a 96 5.7L vortec engine in a very nice 55 chevy pickup. we are using the original FI and ECM with settings to match the non-smog configuration. runs great. however, we used the original style edelbrock water pump that is made for the pre-vortec engines and has the bypass port and is designed for v-belts, not serpentine belts. without a bypass, we had to drill a 1/8th inch hole in the thermo to get some cold water circulation. we had a light-bulb moment this week. why cant we just use the original gasket as a template and drill the hole into the block water jacket just like it existed for the first forty years? your thoughts?
 

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as long as the surface is totally flat, just break out the drill and put the old bypass hole into the coolant passage on the new block.
if you were running a heater, then the hoses to the heater core would be the only bypass you'd need.
 

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Early Vortecs actually had the bypass. Later Vortecs have an external bypass hose. The main problem I see is that the Vortec heads do not have the bypass port in them.
 

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Early Vortecs actually had the bypass. Later Vortecs have an external bypass hose. The main problem I see is that the Vortec heads do not have the bypass port in them.
the only small block heads that ever had any sort of a "bypass" in them was the 93-97 L99, LT1, and LT4 with the reverse cooling setups. every other small block had the same cooling passages in the head, and only the 96-99 vortec 305's and 350's didn't have the water pump bypass drilled in the block for some reason or another. i'm sure GM saved $2 on each engine they made, so i guess it was worth it.
 

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the only "reverse flow" small blocks were the L99, LT1, and LT4's in F bodies, B bodies, and Vettes from 92-97. those were also the only ones that had any sort of bypass on the heads.
every other small block from 55-98- including the truck vortecs and every engine with a serpentine belt and reverse rotation water pump- used the same standard flow cooling setup.
 

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The hole goes up to the deck, too.
 

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my 96 vortec block has the hole drilled in at the bottom and works with my old long style water pump.

my old 79ish 350 i had in the sonoma had the hold in the block also, but when i put the serp. belt drive set up on ( off 96 chevy truck), i had to use the reverse water pump (not lt1 pump, but the serp pump), and it only have the one big hole, not the small one at the bottom. so i had to plug it.



aaron
 
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