[Annixter]

I'm glad the shop got everything sorted for you, and hopefully gratis. To clarify, I was not/am not angry. I was more confused as to why you kept relaying your observations as if you were still confused when I, and others, had tried our best to clarify some aspects of your issues. I apologize if you felt overwhelmed and took my post to be any sort of an attack. I hope this thread has left you better informed about your carburetor setup so that you can better address future issues or just know more about carbs.

 

[kfuller41]

backfires through the carburetor

I have a edelbrock 1406 carburetor that's backfiring through the carburetor on the initial drive of the day when the engine is cold. Once the engine warms up after you have been driving for a few minutes it runs fine, no backfiring. I've had the accelerator pump adjusted and other springs in the carburetor swapped out with no luck. It's a brand new carburetor. The engine is less than 1 year old and it's a 350 long block. Anybody experience this before?

This is a timing issue, check the plug wires to beside they are connected to the correct cylinder. Next check that the plug wires are installed correctly into the distributor cap. Last make sure the distributor is "clocked" correctly making sure the number one cylinder is at the top of its stroke and rotor button is pointing to the number one plug wire.

Hope this helps

 

[jd128]

Is vacuum advance hooked to manifold or ported vacuum? It should be hooked to ported, no matter what other people might claim about the myth of manifold vacuum.

Great explanation of electric choke operation. I was with you all the way until you talked about Ported vacuum. Ported vacuum is an emission control to retard timing at idle to reduce hydrocarbon emission. If your goal is to reduce hydrocarbon emission at idle, use ported vacuum. If you goal is better performance and drivability, use manifold vacuum.

Here is a quote from Lars Grimsrud:

"Some think that ported vacuum advance is "correct", but it is NOT on pre-emission controlled engines. Ported vacuum advance is an emission control technique to increase EGT, which promotes oxidation reaction in the exhaust, but it also increases operating temperatures, increases the tendency to detonate and run-on at shutdown, and increases fuel consumption. With a handful of exceptions, all GM pre-emission engines equipped with vacuum advance used full time manifold vacuum."

http://www.lbfun.com/warehouse/tech_info/timing%20&%20vacuum%20advance/Vaacuum_Advance_Specs.pdf

http://www.lbfun.com/warehouse/tech_info/timing%20&%20vacuum%20advance/vacuum_explained.pdf