The Stovebolt Site Forums The Parking Lot '60-'66 Trucks 61 Chev, "popping" from carburetor

Hey guys, just curious to see if you can shed some light on this..

My truck has a 235 six, I've spent the fall/winter getting it ready for the road, as it has sat for a long time. The engine had an annoying sputter when revved, and would "pop" from the carb (backfire?) So here's what I did...replaced the carb, replaced the fuel pump, fuel filter, checked points, reset timing, changed the plugs and wires, and put in fresh fuel. It runs better now but still sometimes pops out the carb and sometimes out the exhaust. What did I miss? It's driveable and will be on the road in a couple weeks, but I'd sure like to solve this one little glitch it has!

Thanks

Adam

Is it backfiring out of the carb or more like coughing through the carb? A coughing would generally indicate a lean condition.

If it is backfiring (flames and distinct pop) through carb and exhaust, you may have a timing issue and/or a valve problem.

Make sure you didn't go to one of those E85 gasoline pumps. They don't like that. Ask me how I know.

I don't see anything about cleaning the fuel tank. Big item. Also, if anything that's rubber in the fuel system is original to the truck, you need to replace it with something that can withstand todays' nasty gasoline. It still could be a tuning issue, but that tank must be above suspicion, and the old rubber will deteriorate very rapidly.

Sounds like the carb needs adjusting...what carb did you replace the old one with?

Replaced the carb with a remanufactured one from Napa, stock Rochester B. The fuel tank...nope, never cleaned it. I noticed flakes of rust in the fuel filter. Looks like I have to do that next. The popping...I saw flames out the exhaust once. Never saw any come out the carb. It's a pretty distinct pop though. Timing is correct...if there was a valve problem wouldn't it idle rough? It idles and drives really nice, except for that hesitation and pop.

K10, what's the best way to clean a fuel tank?

Gravel. Not sand but small sharp rocks. A little water. Sluice it around for a good long time. Then use a good tank coating. Make sure it is fully compatible with The nastiest of the new fuels coming out. I think the POR 15 product should be up to the task, but with E-85 on the horizon, you need to do your homework and give a couple places a phonecall.
It's gonna take more than a week to clean and reline with all the rinsing and drying and application time.

Oh yea, replace the entire fuel line while you're at it. THEN you'll be in business.

Thanks K10....thinking of simply installing a new tank. Hard to say how much metal is left on the old one judging by the rust being sucked in to the filter.