I got my truck about 3 months ago. its a 1987 pickup model. The previous owner put a chevrolet 305 ci engine in it and so far its been pretty faithfull. But its got a miss somewhere and we cant find it. Every time i give the truck a good bit of throttle it makes a popping noise. Its coming from the carbeurator. I haven't got it proffesionally looked at yet but i'm running out of ideas to fix it. I thought it was the timing so last weekend i did a complete tune up. Changed the plugs, wires, cap & rotor, and the fuel filter. And it fixed nothing. I've played with the cap a little trying to find better timing but it was perfect already. Its an older 305 engine. I'm guessing it came out of an early 80's blazer. It almost sounds like a backfire but its coming from inside the carb. If anyone has an idea of what it could be please send me a message! thanks

 

If the carburetors are fairly easy to take apart, check all your jets, and the factory specs on them.

i recently had a similar problem in my 1974 BMW. it had a very odd miss and wouldnt idle correctly. I did all the guess and check work that you did, and still nothing. i finally took it to a shop and it turns out one of the carb jets was mushroomed by overtightening, and another was clogged, and the idle syllenoids were shot.
I had the work done and now the car runs better than the day i bought it.