Thread: 350 Hesitation Problem

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Ok folks, with all the help in the past on this forum, I hope I can (with the help of you) finally get this Chevy running right. I thank the lord it is not my daily driver.

I rebuilt this engine and have experienced a few problems which I might point out. The timing tab for beginners is not correct, so right out of the box, problem 1. The engine runs great at an idle. I have timed it by ear and sitting in the driveway, in park, it ramps up good. I can put it in gear in the driveway with the brakes applied and she will spin the tires if I let her. As soon as I put it in drive and take off, it will hesitate and backfire (mild). Everything is new, carb, intake, distributor HEI, plugs. The heads were worked at the machine shop as well as the block. The bore is standard, the valves are stock as well as the rockers. My Vacuum is a little low about 12 at idle with no fluctuation on the needle and it comes up to 18 while ramping it up to 1500 rpm and higher. It was an Edelbrock Cam, lifter, carb and intake package for a SBC #2401.

I took it out last week wanting to take my first 100 mile trip and it seemed to be running good for 15 miles or so. No hesitation, great acceleration etc. So I load the family up and about 15 miles into the trip, it starts to run rough taking off from stop lights/signs. If I go wide open it seems to run good. I have the choke bypassed/wide open. Both adjustment screws in the carb are 1.5turns out and I adjusted them to high idle with 1/2 turn back in. I may not have the right gasket under the carb, but it was what came with the kit. That could be my vacuum problem, but you tell me.

Today I jumped in and again tuned it by ear. It was running a little rough so I got it where tt was sounding and feeling good. I put in in drive, applied the brakes everything seemed good. As soon as I put it in gear to take off, it falls on it's butt.

It's like Christine, sometimes it does good, other times not.

Please ask me questions, I'm sure I left something out. And thank you very much for helping!

sounds like you needs to adjust the metering rods....follow the guide in the manual that came with the carb its very helpful.....edelbrock carbs NEVER come tuned properly for your car, even when you buy an engine package from them.... also that 12lbs is very low for vaccum, try and time and tune your idle mixture so that you're getting a smooth idle with 16-18lbs vaccum

when u ramp up on the throttle u are really in ur primary side of ur carb when u punch it u are in the primary and sec. sides of ur carb meaning more fuel. sounds like ur primary is a lil lean and since it is an edlebrock carb some tuning as thesals mentioned will do wonders but remember ignition timing and fuel delivery give the same excact symptoms so set ur timing. if u dont have access to a timing light this the way i do it. turn the distributor counter clock wise till it sounds like the motor starts to pick up on the idle like it frees up but if ur already at that point turn it clock wise till it starts to idle down and do the counter clock wise again until it sounds like it frees up that is max vacuum right there then try running it again and then go for the carb tuning. may sound dumb but thsi is how i set all my ignitions never have a problem

Seems you are dumping solid liquid balls of gas down your carb. My 350 chevy 4 bolt main with a 750 double pumper did the same thing. It was adjusted fine and everything. Turned out to be the grommet seals sold to me by the braided line I bought. The seals were not gas proof and desintigrated. The grommet material got into the jets and just dumped gas instead of atomizing it.

Worked great at idle or 4000 rpms and higher, sputtered and kicked whenever you toutched the gas otherwise. I drove 30 miles in 2nd gear to get to my mechanic's for the fix.

Thanks for the replies.

I will adjust the carb and see how it all works out. A good friend mine told me when I bought the Edelbrock, that it's a carb you'll love to hate. He said I would be adjusting it for the rest of my life!

nah, once you get them set right, as long as you dont make any changes to your engine build you can forget you even have a carb on there for like 10-15 years.... my 69 econoline has been running the same edelbrock carb for 12 years, and still runs just as smoothly as it did when i put the carb on there...