I've subscribed to HPP magazine since 1984-it's a great magazine. I remember that the first Pontiac V-8s had reverse-flow cooling from the factory. Can a standard '65-'79 Pontiac water pump be easily converted back to the reverse flow? All of the heads up to '79 still have the holes in the ends of the heads.Craig RipplingerOtis Orchards, WA
Rocky Rotella responds:
When Pontiac designed its V-8 in 1955, engineers incorporated into it reverse-flow cooling, which directs coolant toward the cylinder heads before dispersing it throughout the block.
The 1955 Pontiac Shop Manual, Book II reasons that maximum cooling system efficiency is possible when cooling the cylinder heads first, which are generally considered the hottest part of an engine. The cylinder heads of these engines contain brass distribution tubes, which direct pressurized coolant toward the exhaust valve seats to lower operating temperature and increase service life. It's referred to by Pontiac as "gusher valve cooling."
Book II also adds that reverse-flow cooling reduces cylinder-wall distortion from cool-water contact, and since the block sees the warmest coolant temperature, condensation is burned off during warm-up, reducing the risk of oil sludge developing.
Pontiac didn't implement engineering changes unless a specific result was sought. The cooling system of its V-8 was revised in 1960, introducing what we know as the conventional-flow path, which was used through the end of V-8 production in 1981, where the block is cooled before the cylinder heads.
The new system was hailed in sales literature as "balanced-flow cooling," and said to direct equal amounts of coolant through both sides of the engine. Another factory source stated that cooling the heads last forces the warmest coolant into the intake manifold, which aids fuel atomization during warm-up and improves cold-weather operation. In addition to what's printed in factory literature, I'd also guess that the conventional-flow cooling system was less costly to produce than the reverse-flow design, and its flow path was more practical without compromising efficiency
Since we know that reverse-flow cooling directs coolant toward the cylinder heads first, incorporating such a system might allow a high-compression engine otherwise on the verge of detonation to operate on available pump gas. While it may seem as simple as installing a water pump and timing-cover assembly that reverses flow direction onto an engine and then making connections to the cylinder-head ends, the block and cylinder heads for either system are somewhat specific, so it's not a simple swap.
I don't believe any company mass pro-duces a reverse-flow conversion kit, but I've seen dedicated race applications where the owner has engineered his own reverse-flow system. I believe you'll find that unique modifications will be required to restrict and equalize flow throughout your specific engine and provide adequate cooling without creating localized hot spots. If you do choose to go this direction, I suggest studying the Pontiac Shop Manuals and incorporating as much of Pontiac's original design as possible.
A point to keep in mind about reverse-flow cooling is that while it may seem advantageous on a high-compression race motor that sees a limited amount of run time, I don't know how efficient or practical it would be to engineer such a system for a street application that sees all types of driving conditions. Pontiac did an excellent job of reengineering its V-8 cooling system, and the conventional water flow path seems to work quite well. If you're presently experiencing cooling issues, it may be less of a headache to make sure the existing system operates correctly.