Cylinders washed need help

fast 99 said:

Go back to basics. Spark, fuel, timing by TDC and rotor position. If all checks out try a new set of plugs. Also check for 12V on choke thermostat. When it runs again set timing, check advances, vacuum, and reset carb idle mix.

Of note, after an engine has been running rich, idle mix will need to be set a couple times until pre-existing fuel is burned off. Will lean out as fuel is burned.

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Ricko1966 said:

The way a power valve works is at low vacuum conditions( the farther you are in the throttle the lower your vacuum readings) so when you step on the throttle your vacuum drops and the power valve adds fuel. Now if you have a low vacuum condition because you have a manifold gasket leaking a base gasket leak,you've cranked the throttle stop screw in too many turns to try to bring the idle up.Now if you are idling at a vacuum level lower than your power valve rating,the power valve thinks you're accelerating and adds fuel. Not saying that's happening,just wanted to eliminate it. If you are pulling decent manifold vacuum at least above 11 the power valve won't open. It's one of the reasons I'm always harping on people with poor gas milage to check their vacuum advance,not enough timing and the carbs dumping more fuel because with the vacuum leak the carbureator thinks you are further in the throttle than you really are.

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Rustisbest said:

Power valves richen the main circuit, so unless your idling at 2500 rpm and the boosters are flowing a power valve doesn't affect idle.

Test Results: Will an Open Holley Power Valve Affect Engine Idle? - CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance - Test Results: Will an Open Holley Power Valve Affect Engine Idle? - Holley Power Valve: Effect of Open PV on Idle I see many comments and ideas about tuning Holley carbs. One of the most prevalent myths about Holley tuning is that if the Power Valve (PV) is not fully closed...

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If the valve is blown or it's gasket is leaking, fuel can get sucked into the vacuum chamber that leads to the hole exposed to the intake manifold in the baseplate. That can cause a rich idle

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If you open the front blades up too far the transition slot gets exposed more than it's supposed to which causes the idle to be rich. Then you wind up chasing your tail by turning the idle screws in to lean it out. All your transition fueling is gone so it stumbles and you try to bandaid it with a squirter that's too large.

You've got a decent bit of adjustment at the rear before exposing the rear transfer slot so that's why I suggest adjusting it for your idle speed. If you need pics of where the rear adjustment is let me know.

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