Power Valve Bad?

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wazoo64

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I had a bad backfire when setting up timing and have not been able to tune the carb right since. It is a new quick fuel and even though it is supposed to handle a backfire I think the power valve may have blown.
The exhaust smells super rich and if I stop the car real fast it will almost stall the engine.
I tried to test by turning idle/mixture screw in and the left side made no change. When I turned in the right side the engine quit. Supposedly if the engine quits when turning in idle mix screw then the power valve is working.

Does anyone know if the engine should quit when only one screw is turned in? When I turn in the left side nothing happens and makes me beleive that the power valve is blown.
 
Have you checked the float adjustment yet? It should just dribble out the inspection hole when set correctly.
 
Sounds like a good idea. I will take a look. If it is more than a dribble does that mean PV is busted?

No, but it will mean that you'll have to lower the float. If the float level is too high, you'll get fuel dribbling out the boosters causing a major rich condition. Let me add that the car must be running when you check the float level.

If this doesn't solve your problem we'll have to look deeper into the problem. Do you know how vacuum your engine is pulling at idle, in gear?
 
No, but it will mean that you'll have to lower the float. If the float level is too high, you'll get fuel dribbling out the boosters causing a major rich condition. Let me add that the car must be running when you check the float level.

If this doesn't solve your problem we'll have to look deeper into the problem. Do you know how vacuum your engine is pulling at idle, in gear?

I will running a vacuum and timing check later today and post the numbers. This setup was running flawless until I pulled the distributor. Long story as to why I had to pull distributor. Anyway, it is running pretty good right now but the exhaust smells so rich it made me light headed and I have a convertible.
 
My Dad Said Turn The Mixture And Idle Screws 1 1/2 Turns Right Before It Dies And That Always Works For Him Almost Dead Boom 1 1/2 Turns Back
 
My Dad Said Turn The Mixture And Idle Screws 1 1/2 Turns Right Before It Dies And That Always Works For Him Almost Dead Boom 1 1/2 Turns Back

I am not sure I understand. Do you mean turn it in from where it is running now, until it almost quits and then back out 1 1/2 turns from there?
 
No, but it will mean that you'll have to lower the float. If the float level is too high, you'll get fuel dribbling out the boosters causing a major rich condition. Let me add that the car must be running when you check the float level.

If this doesn't solve your problem we'll have to look deeper into the problem. Do you know how vacuum your engine is pulling at idle, in gear?
This is what I was thinking too. Also, if the back float is high fuel can slop out of the bowl vent when you hit the brakes, stalling the engine.That was what grabbed my attention.
 
I am not sure I understand. Do you mean turn it in from where it is running now, until it almost quits and then back out 1 1/2 turns from there?
This is much more than an idle mixture issue. Once you fix whatever is causing the severe over-rich mixture(I am thinking float level here) THEN go back and play with the idle screws.
 
This is a tough one because its starting and running pretty well. The response is great once it gets warm. It's just not as smooth on idle as it was before the timing was reset. Any chance the timing is causing it to run a little rich. I dont really want to mess with the timing but I know that has to be right before any carb adjustments.
 
No, but it will mean that you'll have to lower the float. If the float level is too high, you'll get fuel dribbling out the boosters causing a major rich condition. Let me add that the car must be running when you check the float level.

If this doesn't solve your problem we'll have to look deeper into the problem. Do you know how vacuum your engine is pulling at idle, in gear?


I can't remember but if you turn the float level clockwise that lowers the fuel level or is it the other way around?
 
You got it, once you loosen the lockscrew (just a bit or it will spray fuel everywhere, lol) turn the seat adjustment clockwise to lower the fuel level or CCW to raise it.
 
You always set timing first. And then the carb. Any change in timing will affect the carb settings. What did you do to the timing, and why?
 
You got it, once you loosen the lockscrew (just a bit or it will spray fuel everywhere, lol) turn the seat adjustment clockwise to lower the fuel level or CCW to raise it.


You would think they would have changed, modified, invent something that would not let the fuel come out at all doing a bowl adjustment by now. Spraying fuel on a hot running motor is not the safest thing in the world. I caught on to the trick of not backing off of the locking nut as much in order from leaking fuel ... but it's in the back of my mind... FIRE!
 
You always set timing first. And then the carb. Any change in timing will affect the carb settings. What did you do to the timing, and why?

Agreed and good question.

You would think they would have changed, modified, invent something that would not let the fuel come out at all doing a bowl adjustment by now. Spraying fuel on a hot running motor is not the safest thing in the world. I caught on to the trick of not backing off of the locking nut as much in order from leaking fuel ... but it's in the back of my mind... FIRE!

Agreed again. I don't smoke when adjusting floats on a Holley either. :stop:
 
Because my rich condition started directly after resetting the timing I want to make sure the time is right. I have read somewhere that the timing can cause a rich condition. Does anyone have any directions or tech sheets for setting initial timing?
 
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