What is this dohicky on the firewall of my 73 Cuda 340? Has a couple ports on it but mine has nothing attached to it. Pic isn't from my car, circled in red. I've got an aftermarket carb and intake on the car.
The OSAC valve has been used since the early 1970s to delay the distributor's vacuum advance for about 15 seconds during acceleration. Starting in 74 the OSAC valve is on the air cleaner pre-1974 models had it on the firewall. One hose runs from the vacuum of the distributor to the valve, the other from the valve to the carb. Running the hose from straight past the valve will eliminate its limitations, and compensate for a bad valve.
I had to look.
OSAC = orifice spark advance control
https://books.google.com/books?id=dWPGwiivphIC&pg=RA6-PA624&lpg=RA6-PA624&dq=osac+valve&source=bl&ots=AuDRsWE-ZD&sig=T0frp8hs9A6nroBXSU5BYfFXF3M&hl=en&sa=X&ved=0ahUKEwjKzNbt29zaAhUuwFkKHb6ZCvE4ChDoAQgvMAI
My friend bought a new Challenger 360, 4 speed. One trip to the dealer when almost new and a lot of that stuff wasn't hooked up anymore. That car ran pretty well for what it was.
The beginning of all the emission crap!