[John V.]

EGR (exhaust gas recirculation) was a "next generation" emissions control device.

The PCV system was the first emissions control. It was designed to suck crankcase vapors from the oil pan, vapors resulting from ring blowby. These vapors accounted for about 1/3 of auto emissions. It was an easy first step and in my opinion actually improved engine performance (from a maintenance service standpoint) when compared to the old reliance on the road draft tube to eliminate these vapors. And rather than venting the vapors to atmosphere, in most operating scenarios, they were sucked back into the intake to be burned with the air/fuel charge. In certain situations, the PCV system still allowed vapors to vent to atmosphere.

The CCCV system took it one step further by effectively closing the open venting of vapors in all operating scenarios. But it was still only addressing crankcase vapors.

Other emission control devices soon followed as the laws sought to reduce other pollutants.

EGR was among these. EGR is designed to reduce Nitrous Oxide (NOx) emissions in the exhaust gas. It does this by returning a small amount of exhaust gas back to the intake. The exhaust gas causes a reduction in the combustion temp because the exhaust gas isn't combustible. The engine is less efficient but the result of the lower combustion temp reduced the formation of NOx.

I don't know when PMD first started employing an EGR device but I know they had it in '73, the EPA caught them "cheating" because they designed their EGR system to shut down after a short period of time. The EPA was not happy.

My guess is that PMD did not have EGR until at least '68 so I'm guessing Butler is saying their valley pan will not work with '68 and up intakes. Your '64 tripower intake is NOT designed for EGR.

That said, you can buy the repro if you want but you should also be able to score a used original '64 valley cover from somebody with a junk 2 bbl 326 (ie, an engine nobody needs/wants). Maybe post a Parts Wanted ad here.