My carburated 350 runs lean at mid throttle, but idle and WOT seem to be fine. Higher rpms unless I am at WOT will cause popping and misfire. Going down the freeway, if I accelerate, I halfto punch it, or it will misfire and run lean. Coming off WOT it will also pop if I come off it too fast. Coming out of a corner, from idle it will pop. I have been working on this for weeks now and have been through carburation, ignition, vacuum and exhaust. I haven't jetted up yet, but every time I go to buy jets, the speed shops tell me that jets are not my problem. I am being a little vague hoping for your first thoughts. I can be more detailed, but was hoping to avoid writing a novel right off the bat. I am about to break down and pay someone to fix this, please help.:confused:

What carb do you have now? Any idea of what Power valve, jets, etc are in there now?

Hey, thanks for the response. The carb is a holley 750 that I had blue printed last year. It is running a 35 power valve and the stock jets.

Wow, that's a low number (3.5) unless you have one wild cam in that thing.

If you have the capability to drive with a vacuum gauge, and note the vacuum you have while cruising, that will help determine the PV # you need. If you don't, use a vacuum gauge with it in drive, foot on the brake, and take half that reading - that should be a good start # for the power valve.

Thanks, I was going for a real lopey hot rod kind of sound. Vacuum tuning is how I came up with the 35 number. The cam is a comp 270H. It was the largest I could get and still run a stock converter. I am still running old iron heads with an estimated 9.5:1. I am also running a timing gear and no x pipe in the exhaust, which ends right before the axle. I have since added 4.11's, a 200R4 with a 2200 stall, and 18" rims. I also have an O2 sensor, so I can see exactly where it starts to lean out in the throttle position. I have also been changing throttle cams and finding little success. With the throttle cams, I have been able to make the condition worse, but not better. Could this maybe mean I have an issue with the accelerator pump?

I'd bet you need to richen your primaries (beyond where you may want them) to solve this problem. There are ways to get into the carb itself (drill/tap, etc) but that's beyond me.

I'd still increase that PV number - it doesn't open at idle anyway, unless something else is going wrong.

thanks, I went on my hunch lastnight I replaced the acceleraror pump and upgraded to a 50mm. It definately increase the fuel all the way through the throttle, but it seems to just have masked the problem with gas.It was exactly the same performance curve, but is all richer. It was so rich, it stumbles on anything other than mid throttle. So I guess I just confirmed it isn't a lack of fuel delivery. I then retarted it back 2 and it got worse. I will try advance timing tomorrow. I am also going to pick up a 65 PV. A stock one hasn't worked in a couple of years, but maybe something has changed.

I let a professional tuner Flog The CRAP out of my car on Friday and what he said to me was "Your car sounds real fast, but it runs like a dog. Your transmission slips, and you have either an ignition problem, a problem in your heads, or a flat lobe on your cam".
In response to this, I pulled the plugs, ran compression tests, checked the pre load and my friends and I just watched it run without the covers on. The valve train seems to function with no noticeable issues. I have not replaced the distributor, but another user here rrfd43 who is chasing the same problem has.
Other than a 350, we have almost none of the same parts on our engines, but our performance problem is the same.
I attached a couple of pics of the spark plugs from this weekend. The plugs are 1 weak old and have about 200 miles of daily driving on them.
Can anybody here read these?