Went for a run today, about 10 minutes after I'm on the highway, my 235 Chevy starts running rough in a strange way. If I give it "the gas" it runs just fine, back off and it stumbles and feels rough. Turned around to come home and after another 10 minutes it was way worse, backfiring out the tail pipes, but still ran well if I kept my foot on the loud pedal. It's been running super sweet for over 12 years!, just got back from a 1200 mile road trip without a hitch and did a few shorter runs in the last couple weeks with no signs of any problems. Now this. 235 with dual Rochesters on Offy intake with water cooling, Fenton headers, Langdon HEI (with fresh cap, rotor and plugs about 2500 miles ago). No smoke of any sort out the exhaust, no oil usage in last 1000 miles, no change in coolant level in last 2500 miles. Pulled the plugs ( they're OK), checked compression (OK), found a small vacuum leak (fixed), pulled the air cleaners off the carbs, found a lot of liquid gasoline in the rear airfilter, tightened up everything on the carbs, manifolds, etc. nothing in particular was loose. Idles "okay" but I can tell there's a miss in there somewhere cause she's shaking a bit and a bit of a pop out the exhaust. Any clues? Sending it to my mechanic on Monday.
You're probably right pinky, they are 14 years old and have about 45,000 miles on 'em ... however just seems strange that it would happen so quickly, i.e. fine one day and crap the next ...
My first thought. You didn't happen to stop at a different than your usual gas station? Like an old one that has had the tanks in the ground for many many years? crap in the gas or crappy gas is one thing that causes issues like that.
I had a weird fuel issue in my car and it was caused by a rotting soft line between the frame and engine... it was sucking a bit of air. The car ran ok til it got hot and then it would behave like vapor lock. I was getting pressure but not enough. Check those lines. Posted from Jalopyjournal.com App for Android
Sounds to me like the jets are plugged. Rebuild your carbs, or at least blow out the jets, and then make sure your fuel filter is replaced or cleaned. Is your gas tank in good shape, no rust, etc? I have a rusty tank on my vw running dual carbs and get this alot, just like you described. Constantly cleaning out filters and jets. Just my .02
Current tank of gas is from my local Shell station where I buy it regularly, always fresh, though this tank was Regular and not the usual High Test.
Yeah but it's the weekend and I don't happen to have a garage to work on the truck in ... my mechanic's fair and reasonably priced.
Quite a bit of liquid gas in the air filter housing of the rear carb, suspecting a stuck float maybe? Not about to take a carb apart on a Sunday in my driveway.
Tank has never been pulled that I know of, so no idea of condition, but the truck has run fine for me for 23 years. That said, the recent long road trip with some nasty bits of Interstate might have knocked something loose in the tank and it's taken it's time making it's way to the carb. Thanks.
Have sticking float problem on my Willys. It'll leak and I just slap the carb with the handle of a screwdriver, float good after that.
Thanks for all the suggestions guys ... it was simply dirt in the rear carb. Simple old school solution for an old school problem. Pinch the rubber fuel line til the motor almost stalls, then let 'er go. The surge of gas flushes out all but the most stubborn crap stuck in the carb. The dual carbs made the dirt-in-carb problem less than apparent ... one carb still functioning normally allowed the motor to run okay, second carb over-filling with gas was sending volumes of raw fuel into the rear cylinders. So we've plumbed in some new filters and replaced rubber fuel lines, just to be on the safe side.
nice easy fix! I always put emphasis on fuel filters as well. I have one on before my elec pump, and one after. They are cheap, easy to replace, and prevent that crap getting into your jets.
Funny thing is the fuel filter is the only thing I didn't replace before my long road trip, stupid auto parts store didn't know what I was talking about, they needed a part number or a year/make/model and their listings didn't go back into the '50's ... it's just a plain ol' inline fuel filter for #&@& sakes !
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