Early Pontiac V-8 Engine Cooling
By Larry Gorden
Beginning with the first production engines in 1955, Pontiac V-8 engines were cooled by reverse flow meaning the cooling water enters and cools the heads first and then some of the water enters the block and cools the cylinders.
In 1960, Pontiac abandoned the reverse flow system in favor of “conventional” flow where cooling water enters the block first and cools the cylinders -- then all the water flows into the heads, cools the valves, and returns via the intake manifold to the radiator.
difference in reverse flow and conventional flow is in how water circulated
through the engine, not how it circulates through the radiator.
In both cases, cooling water is taken from lower radiator and hot water
is returned to the top of the radiator.
Each system of cooling is explained below.
The following is found in the 1960 Shop Manual. I added the photos and highlighting.
I’ve compared closely a 1956 block with a 1960 block (reverse flow with conventional flow) and 1957 heads with 1960 heads. I would expect the same differences between a 1959 and 1960 block/heads. Differences I see are:
Reverse flow heads must have the water distributing tube installed in each head. The 1960 heads do not use them. 1960 heads can be used on earlier years by installing the tubes. Earlier year heads can be used on a 1960 engine by removing the water distributing tubes and installing a freeze plug in the head inlet water passage. I compared 1957 heads with 1960 heads and there is not apparent difference.
The front covers (timing chain cover and water pump housing) are completely different but either front cover will bolt up to either block (same bolt pattern and same front seal) -- but due to water flow differences, they must not be interchanged.
Front Covers (1960 left in each photo, 1957 right in each photo)
(1960 left in each photo, 1957 right in each photo)
Note on the backside of the 1957 front cover (on the right) that the large holes are closed although they may appear to be open water ports.
The Front of 1960 block
does not have the two holes for water return from the block into the front
The block head mating
surface (deck) has different ports for water passage between block and head.
The upper front first three water ports that you find on the reverse flow block
are missing on the 1960 block on each side. Ports towards front and on
bottom of deck are smaller on the 1960 block than the reverse flow blocks. This obviously is to force
more water to the back of the engine and to lower side of heads to provide
controlled cooling for the 1960 engine. The 1960
Shop Manual says " " which
likely refers to this change in water ports.
The upper front first three water ports that you find on the reverse flow block are missing on the 1960 block on each side.
Ports towards front and on bottom of deck are smaller on the 1960 block than the reverse flow blocks. This obviously is to force more water to the back of the engine and to lower side of heads to provide controlled cooling for the 1960 engine. The 1960 Shop Manual says "water transfer holes between the block and cylinder heads have been designed to provide an equitable flow of coolant
" which likely refers to this change in water ports.
1960 Deck (click for enlarged view)
The 1959 Shop Manual talks about why reverse flow cooling was used and extols
the benefits of reverse flow and gusher valve cooling. Why did
APPARENTLY MOVED AWAY FROM GUSHER FLOW, PRIMARILY BECAUSE THE ENGINES RAN TOO
COOL IN COLDER CLIMATES”
Source: Rick Gonser POCI Chief Judge, Western District Director, and 50s/60s
That theory doesn’t (dare I say?) “hold water”. If a hotter engine is needed, why not just replace the thermostat? To change the basic flow design in order to make the engine warmer just doesn’t make sense.
A lot of the reverse flow engines are still running around. I haven't heard of any issue with corrosion in the engine. So that theory doesn’t make sense.
Theory 3: Pontiac
made the change
Theory 3: Pontiac made the changeto free up the fronts of the cylinder heads for accessory mounting Sources: Pontiac Jack and Charles Coker
This could have been done to allow mounting more accessories outboard of the engine and thus allow for lower front hoods.
I'm not sure I buy it. The elbow and short water hose on the front of the engine didn't take up much space. Plus the hood was lowered considerably in 1959 when they still used reverse flow cooling.
This theory is based on what the switch really did differently in cooling the engine. The 1960 engine will provide much better cooling around the cylinders than the old reverse flow system. All the incoming cooling water will flow around the cylinders before exiting the block and going into the head to cool the valves and combustion chambers. Water cools the cylinders first where it warms up a bit, and then the water cools the upper end (heads).
this Theory 4 correct?
Maybe not -- I've not heard it from anyone. It would make sense only if
Reduction in manufacturing cost has been offered as another possible reason for the switch. So far, I've been unable to find anyone that can verify the real reason for the change.