Cylinders washed need help

Ryanbrown36 · Tuesday at 7:58 AM

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.

Ok thank you for help!

Ryanbrown36 · Tuesday at 8:02 AM

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.

It’s very likely that low vacuum could my my problem when it comes to running rich as I believe everything else is set properly but have no idea how much vacuum. Thank you for the help!

Rustisbest · Tuesday at 1:36 PM

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...

www.corvetteforum.com

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

You must be registered for see images attach

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.

85K304SPD · Tuesday at 4:46 PM

Don't forget to lean it out one jet size for every 2000 feet in elevation you are at above sea level. Power valve should be half of idle vacuum. That plug looks like it is pretty rich.

Ricko1966 · Tuesday at 5:05 PM

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...

www.corvetteforum.com

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

You must be registered for see images attach

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.

I've always known about the transition circuit,people jack that one up all the time,but also assumed if the power valve was opened from low vacuum it would be rich,from the times I've had holleys with blown power valves.Hmm thanks for the article and the knowledge. I'd like to see that same test run on a car with intake leak and the stop screw turned way in to try to make it idle,it still seems it would pull fuel.

fast 99 · Tuesday at 5:07 PM

............and all it takes is one backfire to blow a PV.

If it's a Holley PV is bad/leaking, to those who dislike Q jets joking. I have a couple Fords with Holleys.

Rustisbest · Tuesday at 6:20 PM

......and Holley remedied that a long time ago with a checkball in the baseplate. Welcome to the early 90's lol.

Of course we couldn't have a carb thread without the quadrajet being brought up. Let me see if I can remember how it goes
-tuned for your engine!
-engineers are smart!
-GM updates!
-my cousins brothers nephews former
roommate is a wiz with qjets!
-buy Don Rickles book!

All in jest of course :rofl:

Craig Nedrow · Thursday at 9:25 PM

Matt, I appreciate that article, I think you are the one that brought it up. I'll say it again, study, I have several holly books, and forums like this are a HUGE help.

Rustisbest · Thursday at 10:27 PM

Craig Nedrow said:
Matt, I appreciate that article, I think you are the one that brought it up. I'll say it again, study, I have several holly books, and forums like this are a HUGE help.

Glad to help and i couldnt agree more on the studying part. There's free downloads here for anyone interested

Free Carburetor Repair Manuals

www.carburetor-parts.com

Look under Holley 2300 and Holley 4150/4160

Some of the info is the same in both. The Holley 2300 is in color though and the circuit diagrams where it breaks down the which is air/fuel/mixture of both is helpful to a visual learner like I am.

Its a 1959 manual so there are a few differences (like the idle bypass adjusting screw in the pic is posted earlier) but for the most part they're the same as today's Holley

Ricko1966 · Thursday at 11:01 PM

Rustisbest said:
......and Holley remedied that a long time ago with a checkball in the baseplate. Welcome to the early 90's lol.

Of course we couldn't have a carb thread without the quadrajet being brought up. Let me see if I can remember how it goes
-tuned for your engine!
-engineers are smart!
-GM updates!
-my cousins brothers nephews former
roommate is a wiz with qjets!
-buy Don Rickles book!

All in jest of course

Wouldn't your cousins brother also be your cousin?

Cylinders washed need help

Ryanbrown36

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

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