All first off my engine is a 305 now carbeurated v8. I think it used to be FI but that was just a guess that my mechanic told me when we were putting in a new lower intake gasket. It's also got the 5sp manual.

For quite a while it was running fine, but at a steady speed/RPM it would lurch, sometimes even gaining rpms, but usually just little lurches. Uncomfortable, but it ran. It was also pretty loud due to my lack of exhaust.

About a day ago I didn't drive it all day. The next day I was driving it around, and it seemed quieter. Also it hasn't been lurching since then. My mechanic had said the float was probably stuck in the carb before and we never bothered with it (no free time to deal with it) Oh forgot to mention, it used to idle solid at 500-650. Now it can vary anywhere from 450-750. Nearly dieing out when under 600 so usually I'm keepin the gas on a bit for 800 when idling.

So I'm just worried maybe a cylinder died on me or something. I haven't noticed a big decrease in power but *maybe* a small one, or it could be my imagination. It is definately quieter, and the non lurching is nice. It runs like I'd want it to, but since nothing has been done to it it's got me questioning what happened. Any ideas?

 

I'm not too experienced with this but maybe it is something simple like a bad spark plug, fuel pump, fuel line. Maybe your mechanic can easily check these plus cylinder pressure. Not sure if your car has IAC or TPS sensors but they could need adjusting too. Any wierd smoke comming out of exhaust? Are your belts good? Are you using up a lot of oil? I'm going to assume the lower intake gasket was put on and sealed properly.

How to adjust IAC and TPS https://www.thirdgen.org/tpimod2

 

Yes, I was there with the whole procedure, and they went on great. (by the way my mechanic isn't a shop one so we can't check pressure, he's just highly experienced and is my neighbor.) I have no idea what IAC or TPS sensors are. Spark plug would be a pain seeing as how my headers have to come off for that, and I don't want to do that, and the shop wants 300$ for it so unless its needed I don't want to do that. Belts are fine, don't see any weird smoke off my mostly lack of exhaust system. I don't think it's fuel pump or lines, or at least nothing major with them since I still have normal fuel flow. Thanks for your ideas and I'll read the thread.

Edit: I don't see how throttle body affects carb? Unless the carb works the same way. But I haven't brought this to my mechanic yet as it seems to be ok, but I will over the weekend. Any more ideas from anyone?

 

Edelbrock carb like your sig says?
If so, no TPS or IAC - so nothing there to check.

Is there an in-tank fuel pump, or a mechanical pump on the block?
If in-tank pump, was a RETURN-STYLE fuel pressure regulator used?

You can get a compression test kit pretty cheap at most any auto parts stores, or Harbor Freight.

What's timing set at?

Using an aftermarket HEI distributor with vacuum advance I hope.
Removing vacuum line and plugging it to adjust timing?

Did you pull the plugs to see them?

You don't have any vacuum lines connected to any fuel pressure regulators do you?

 

Is the carb running ok? Do you have a PCV valve on your driver side header? That could affect idle. $2 for a new one at parts store. Harbor Freight sells compression and fuel pressure test kits for cheap. Are your air & vacumn hoses attached soundly and have no leaks? Maybe one is loose where it connects to carb or intake manifold. I think they sell a cheap spark plug tester where you hook up tester to end of plug in engine.