Originally Posted By: javacontour
Was the flap part of the mandate in 1975 for cars that used unleaded gas? The unleaded nozzles had to be smaller so you couldn't put leaded gas into a car that required unleaded. I wonder if the flap was part of that regulation?
Exactly correct - in 1975 when unleaded gas came on the market, it was more expensive than leaded gas, so people being what they are with the price of gas, the fuel filler was made incompatible to stop leaded fuel from going in the smog dogs.
The leaded fuel was also said to breakdown the catalytic converter and reduce its efficiency, and thus was further justification for the new fuel system. I have no knowledge of that, but I know those early cars stunk like rotten eggs (H2S).
I was a teen age gas pumper then, and even if I didn't recognize the exact model of car, I knew when to grab the unleaded pump from the stench of the exhaust. Many people used a pair of pliers to rip the neck adapter out of the filler cap so they could use the cheaper fuel anyway, and had the convertor cut off at a muffler shop.
I don't know when leaded gas finally went away around here - early to mid 80's I guess. Seems like the Veeder Root mechanical pump computers went from three price wheels to four price wheels about '73 or '74 - I think it was before no lead came on the market. An old building I renovated a few years back had a stack of several hundred three wheel Veeder Root computers in it, still in the box, probably pulls from pumps that went four wheel. I sent them to the scrap metal recycler.
edit: doh - you're talking about the flap, not the necking down device, my bad. I don't recall if the early smog cars had the flap or not. I think that they only had the necking device, but it's been a long time. It seems like my '75 Firebird had a screw on gas cap, as opposed to the earlier cars that had more of a bayonet fitting for the cap.
I still have a '79 Sedan DeVille in my stash of old cars that we no longer use, but never bothered to get rid of, so the next time I am out at the shop I'll try to remember to take a look at the filler on it.
Whew, I feel old after that trip down memory lane.
