Ok I cant figure this out and wander if anyone has any help. I drive my truck to work every morning at 6:15 and it is a 20 mile drive and the temp outside is around 50 degrees and has been all week. i get started up just fine and head on my way the truck runs perfect and everyday this week at exactly the same point at about the 8 mile mark the truck pops through the carb hard just once and then continues on its way just fine never to have any problems the rest of the way to work or back home. my routine is the same and its freaky i bet within
a hundred yard stretch of the road every morning it does this.
this just started this week. Ive had the truck about 6 months and this just started. it is a 1975 f-100 automatic with a 360ci.
the week i bought the truck i put a new 2bbl. carb, coil, wires,plugs,fuel filter,air filter, checked and set timing and carb, w/ help from this forum which worked great
and anything else i could find to change on it since i was driving it everyday.
and it runs perfect other than having to feather it out of stop signs a bit to get it rolling not too bad just a bit. other than that perfect.
Any Ideas?

 

Does it do this when the temps are warmer? Do you have an electric choke or manual choke? This is just a guess, and I'm assuming you have an electric choke. Since the temps are cool, and you're doing the same routine, and you're not having the same issue in the afternoon when the temps are warmer, I'm thinking the choke is binding or sticking. When the choke coil finally exerts enough pressure on the choke plate, it snaps open suddenly, instead of gradually, changing the mixture, causing the "burp". I'd try spraying the choke linkage with penetrant and working it by hand, feeling for any binding or rough movement. Or move the choke housing adjustment a small amount one way or the other to see if it changes anything. Just a guess, and it's cheap and simple to try.