The 460 in our motorhome [87 FORD E 350 chassis] backfires thru the carb when it's in a hard pull. I pulled the car on the trailer today with it for the first time and found this out. It seems like when the secondaries on the carb open up, [Ford Holley 4 bbl], is when it does it, like it could be leaning out. As long as it's not pulling hard, just running a steady speed, it does fine. What do I need to look for? Tune up? Carb need rebuilding? Something else? Any ideas on where I need to start checking? Thanks
Sounds like it's going lean. My Fiat did the same thing when it got water in the gas. Would run fine just driving along, but if you got in it, it would pop and spit through the carb.
I would agree with Jamie,sounds lean under load to me.Also just for the heck of it check the timing.Also,What the heck are you doing with the thing floored while your towing anyway!!!!
Not floored, just about half pedal.......It may be some old gas left in it. We just got it about a month ago, don't know how long it had been sitting before that, but the exhaust had that old gas smell. We filled it up on the way home, drove it about 100 miles, filled it up again. We took it on another 100 mile or so trip, then the 40 mile trip today, and filled it up again [20 gals at $3.75 a gal, yikes! $75.00!} It has about a 38 gal tank. Exhaust no longer smells of old gas, have used fuel treatment in every fill up except the first. It pulls good until it starts popping back thru the carb, then you have to feather foot it......
I wonder if you are getting water into the carb.... If water gets into the tank (condensation, rain etc.) the alcohol in the gas will separate out and cause the kind of problem you are having. It is basically a lean backfire because the amount of fuel is too low for the air being drawn in. If you have a manual choke try closing it a bit when it starts back-firing and see if that fixes it. You can also pull the tank drain and drain some fuel out into a mason jar (or other large jar). If the fuel in the jar separates with clear liquid on the bottom then you will have to drain out the fuel until you get only gasoline.
change the fuel filter... my 68 galaxie used to do the same thing about ever 30-60 days it would start popping back through the carb if I pushed the accelerator too hard going up hill.. it happened to have sat with gas in the tank for too long before I bought it and gummed up a bunch of stuff. but as long as I kept the filter changed it kept running for a few years until some gunk got through to the carb and intake, then the filter change didn't help any more
I'm thinking the carb secondaries aren't letting any fuel in. Friend of mine has a dually with a 460 that was doing the same thing, he put a new 600 Holley on it and solved the problem. May try putting a kit in it over the winter, need to get it right before show season!
My suburban did that, swapped ignition module cause I thought that was the problem.Then when that did not solve it, I was convinced it was fuel related. Carb rebuild etc. No change. Changed cap and wires and problem went away. Resistance is a bitch. Dan
Good thoughts, Dan. I've got all winter to play with it, between doing the body and paint on the Mav, starting on the 82 stepside, and brakes and steering on the workhorse 84 stepside. Now if I could just get some of that $700 billion the govt wants to spend on the economy, I could get things done a lot faster!
