[BruceWilkie]

Thought I would share some info and pics how it was originally intended and how to make it work on something like 6x heads on a 59 block.

Pontiac originally used a reverse cool scheme in 55-59. They pumped water from the radiator outlet thru the pump and directly to the cylinder heads. The early heads had provision for "sprinkler" tubes that drizzled water over the exhaust side of the head(internally). The tubes also acted as flow directors to move water to the back of the heads. Some water flowed down into the block but majority flowed from rear of head at the end of and outside of sprinkler tube and entered the manifold crossover then on to the radiator.
The thermostat bypass was NOT at the crossover! The 55-59 timing cover is blocked at the large water holes of the block face. The 59 block and pump in these pics shows the 2 "extra" small holes below the large block face water holes. These holes served as the thermostat bypass AND provided some flow current so the water in the block wouldnt stagnate. A very effective cooling scheme but cost to manufacture plus extra service parts led Pontiac to the more conventional cooling scheme used from 1960 on. Not as effective but effective enough for production/warrantee purposes.

Now here comes the part about how to utilize the reverse cool scheme without heads that can accomodate sprinkler tubes.

Surprise my 6x heads have bolt holes near the front head freeze plugs. The original hoses and water necks bolt right up! Of course that was too easy! You will see in my pics the freeze plug hole is slightly offset to the water neck holes. 2 minor issues 1) slight restriction, 2) probably leak.
One of my pictures I drew a yellow line around the waterneck/freeze-plug to illustrate the issue.

I have space to move the waternecks forward of the heads thanks to the hoses so I will be making a spacer plate to seal from leakage and offset the bore so I wont restrict flow.

See "template" pic.

Next issue. Without a sprinkler(distribution) tube water would want to take a BIG shortcut at the manifold water crossover. Solution, block crossover holes in head with freeze plugs! At the rear of the head I will have to plumb lines and bring the water back to the crossover. I'm going to use the rear freeze-plug/heater nipple location on rear manifold face of heads probably a pair of #10 lines and fit them to the manifold crossover.

Water will flow across the heads front to rear then back to crossover(via return hoses) and some water will be flowing into the block from the heads just as the original 55-59 did. My modern intake will need the bypass hole plugged.

I've got plenty of pictures and the titles should help explain. Also markings on the pictures should help as well.