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Discussion Starter #1
I have a 350 SBC in my 1970 Nova. Here's the specs on the engine:

1) 1974 block, 4 bolt mains, steel crank, stock heads/manifold.
2) I have headers and dual exhaust, not the stock exhaust manifolds.
3) Stock Rochester 4BBL.
4) Radiator and fuel filter are new.
5) Stock air cleaner.
6) Standard points distributor/stock cam/timing components.
7) Powerglide transmission, all stock gearing, engine is less-than-mildly built.
Not sure about the actual mileage on the engine.

Here is my issue. When cold, the engine easily fires right up. It runs, sounds, and idles great for about a half hour under normal driving conditions.

I don't get a temp light, and the engine seems to run at normal temp, although I don't have a temp gauge at this time.

After about a half hour, the engine starts to idle roughly and sometimes stalls. If I give it gas it seems to rev ok, but the idle sounds horrible. I can smell raw gas, not too bad but it's there.

I know of a handful of things to check, just not sure about priority. For example, what are the most obvious things to check first? Plugs are probably in need of changing, but is this really what could be the problem? I am suspecting a carburetion/choke issue based on the gas smell, but I'm not too sure. Car is on its second 350, and both of them seemed to have this behavior. Or, perhaps the exhaust is too close to fuel lines? Any help is appreciated.
 

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That's what I was going to say. Your choke is not unloading. Take the air cleaner lid off and look. One of the problems when putting headers on is you negate the hot air cross over. The heat from exhaust operates the coil that works the choke. If it's not getting hot, the choke will stay partially closed.
You may need to convert your Quadrajet to an electric choke.
 

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ever thought about the Olympics ??

don't they have a quadrajet throwing competition in the olympics ?? lol Thats what i've done with everyone i used to get ,,, put a holley on it and ease your mind.
 

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Discussion Starter #6
I have a 650 Holley double pumper w/an electric choke that I totally forgot about, but before I go through the intake/carb swap, I wanted to verify that my issues were strictly related to the choke. What I ended up doing was starting the car (with the stock intake and rochester) and I let it run for a good half hour. Once it started acting up, I opened the choke butterfly as open as it would go and the car ran like garbage - it only seems to run semi-ok (once warmed up) if the choke butterfly is still pretty closed up. Does a car normally run once warm with the butterfly wide open, or does it stay closed a little? I guess I never bothered to look because mychoke linkage is broken anyways.

But even aside from messing w/the butterfly, it still doesn't seem to run as well as it dies when it is cold. I messed around with the idle screw a little bit but it still sounds like it wants to die on me. Plus, I started hearing a sullen backfire/pop coming from a cylinder on the odd numbered side of the block. Perhaps one the plugs/wires is hosed or I have a timing issue, or maybe the carb fuel mixture is out of adjustment or is in need of a good rebuild/cleaning.

I am going to swap out the carb and intake, but suggestions on any other things to check in addition to those things would be helpful. Thanks again all for your help.
 
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