How Pontiac cooled the heads in 1959. Yes its a factory Pontiac V8 in GMC truck. There is a pipe with holes in it slid inside each head front to back which ensures cooler water makes it to the rear of the heads, and more even Temps. These pipes didn't fare well with corrosion and Pontiac stopped this sometime in 1960 and went with what Chevy and others did pushing it up through the block up into heads.. That said Chevy used 1 inch or bigger holes, Pontiac did not. Hence the 421 mods.
