[LMSRACER]

Originally Posted by jm455ho

Sorry, mistyped the number of 5/16" holes. There are 5 per deck. Total of 10 holes per deck as per factory block dimensions. See attached drawing. The heads have more cooling holes.

Actually I'm glad that you posted this illustration.....

It shows what the Pontiac Engineers were doing to ensure that the coolant would tend to make it to the rear of the block and cylinder heads. Notice that the size and placement of the holes are biased towards the exhaust side of the block and cylinder head and also notice that the holes get progressively larger as they reach the rear of the block.

This was their way of getting the greatest coolant volume into the exhaust side of the cylinder heads and to ensure that sufficient coolant would make its way to the rear of the block and heads.

Anyone that drills their own holes in an aftermarket block should seriously consider the number of holes, their size and their placement.

Everything that we do or recommend relates to improving upon what the factory was trying to accomplish. Yes, they were biasing the coolant flow towards the exhaust side and towards the rear of the block, but that doesn't ensure that the coolant is actually circulating readily through all of the various cavities in the cylinder heads and block. There needs to be properly sized and positioned exit paths for the coolant to pass through to ensure the elimination of trapped air and to ensure a proper volume of coolant for "Effective Cooling" purposes.

In an aftermarket block that comes dry decked, the customer or engine builder needs to consider whether or not the engine is a street car application with a thermostat and heater core or a racing application without the thermostat or heater core.

In a racing application the location and sizing of the holes through the block's deck surface can be much more symmetrical front to rear. Although I'd still drill larger holes along the exhaust side of the deck and smaller holes along the intake side of the deck. Then you can control the coolant flow from the front, the center and from the rear with the coolant exit fittings in the cylinder heads.

Thanks,
Larry S.