Hey guys, I have a '73 model 440 that suddenly wants to drop from around 1200 rpm to about 500 rpm while idling and then return back to 1200 and then drop again. If I put it in drive the rpm will drop all the way down to about 300. I tried putting new plugs and wires in. Now it just does it more rapidly. I used the Champion Copper Plus RJ12YC plugs that did seem a little shorter than the Autolites that I took out, but they were the recommended plugs from Auto Zone. I've never had this problem before. I put a light on the engine and got it adjusted where it sounds pretty smooth and then the rpm will just plummet. I thought maybe the fuel filter, but it is fairly new. I haven't tried cleaning the carb. Any thoughts would be appreciated. I'm still a rookie when it comes to engines just fair warning
Thanks!