440 vaccume problems

[Eddie]

Guys I just recently fired my 440 for the first time and it seems that when I hit the throttle it wants to idle high not comming back down but if you let it run it will idle back down but it takes some time to do so.I think it has a vaccume leak at the carb base.The big problem that I dont understand is when its running and you pull off the oil cam you can feel it pulling in a vaccume and you can hear it suck in air when the cap is removed I did install a pcv valve but it is still making alot of vaccume in the engine at one point it was blowing oil up through the bolt holes in the valve covers how do I remedy this problem.The engine is fresh and only has about 2 hours run time so I thought maybe the rings are still seating in.Any info would be greatly appreciated...Thanks,Eddie

 

[67 coronet]

your idle up problem sounds like a choke adjustment issue.what is the actual vaccum at idle?blowing out oil could be a crankcase presure problem.you said you have a pcv,what is the breather setup on the other valve cover?

 

[65affair]

What carb are you running... If its a holley, it sounds like the power valve is incorrect for the vacuum @idle. did you put a bigger cam in the new rebuild?

 

[Eddie]

no breather set up on the other valve cover yet.I installed the mopar performance valve covers and I drilled the drivers side and installed a pcv valve but havent done the passenger side yet.The original type cover went to the airbreather on the carb.

- - - Updated - - -

What carb are you running... If its a holley, it sounds like the power valve is incorrect for the vacuum @idle. did you put a bigger cam in the new rebuild?

I am running a 750 holley and it is a 484 purple shaft cam.Not sure what power valve I need but I did call holley tech and man was that a waste of time,there was so much back ground noise you couldnt hear and what i did hear i didnt like.He told me to set the choke but the choke is not the problem.Would you know what power valve I would need for the 30 over 440 with a 484 lift cam.thanks

 

[Hemi Rebel]

Oil cam? Not sure what you mean by that. If there is a vacuum inside the engine, it sounds like you have an intake manifold leak. It would have to be under the valley pan. That or the pcv valve is stuck open. But that would not explain the oil coming through up through the bolt holes. I always put sealer on these bolts, but having a major vacuum draw should prevent this. You would need excessive crank case pressure to push oil out. Unless, was it all the bolts that had oil coming out? Or just 1 or 2? If there is an intake manifold leak at the mating surface between head and manifold that could possibly draw oil to that area, and it could wick up the bolt threads. Just brainstorming for possabilities here.

 

[moparmarks]

With the motor at idle put you hands over the carb and try to choke to off. If it chokes off then you probably don't have a vacuum leak. If the rpm increases then you have a good leak. Probably at the intake like Hemi Rebel said. Can use some starting fluild or a torch to go around and try to find the leak. Leak could be in the carb too.

- - - Updated - - -

Need to take a vacuum reading to pick a power valve.

 

[Eddie]

Oil cam? Not sure what you mean by that. If there is a vacuum inside the engine, it sounds like you have an intake manifold leak. It would have to be under the valley pan. That or the pcv valve is stuck open. But that would not explain the oil coming through up through the bolt holes. I always put sealer on these bolts, but having a major vacuum draw should prevent this. You would need excessive crank case pressure to push oil out. Unless, was it all the bolts that had oil coming out? Or just 1 or 2? If there is an intake manifold leak at the mating surface between head and manifold that could possibly draw oil to that area, and it could wick up the bolt threads. Just brainstorming for possabilities here.

Sorry but where I said oil cam that is supposed to say oil cap.LOL.... I am runnimg a mopar single plain intake with a valley pan and I did torque to specs.I will check for a leak at the carb first.I hope its not at the valley pan.

- - - Updated - - -

Thanks for the info I will check it out sunday.I do really appreciate the info you guys are sharing.Thanks

- - - Updated - - -

I am running a 750 holley.How do I find out what power valve to run

 

[65affair]

You need to check vacuum at idle, what ever that is say 12inches, then divide that in half to "6" and you find a power valve that is = or < 6. by checking the vacuum at this time you can watch the vacuum gauge to check for vacuum leaks. The power valve is located in the metering block. the power valve controls the change over form the idle circuit to the Run circuit of the carb. so, if the power valve is to big (say 8.5 and you need a 6.5) it will not stay closed properly letting the "run" circuit engage during idle. there is your fast or erratic idle.

 

[coloradodave]

Not exactly a correct explanation of the power valve's function but correct on the way you choose the right valve for your motor.

 

[Eddie]

I did a vacuum check at the back port on the carb because the mopar intake has no vacuum port.The reading was between 5 and 6 so I ordered a 2.5 power valve and replaced it and it still idles kind of high after reving the engine.I pulled the vacuum advance hose off and it idled down right away so I am thinking it is the vacuum advance,that will be the next step I will take and see what happens.The vacuum advance seems to be a hard item to locate but I did find one at oriley autoparts but it will not be in until friday.Thanks guys for the info and I will update once I change out the vacuum advance.

 

[65affair]

If the car idled down after you took off the vacuum advance hose the the hose is connected to the incorrect place on the carburetor. The vacuum advance should be connected to the "Spark Port" of the carb which is the port in the metering block. that port dosn't have much vacuum until you rev up the engine.

 

[coloradodave]

65affair: If you do a search you'll find a really good explanation as to why the vacuum advance should be hooked to FULL manifold vacuum, not the timed spark port as you suggested. Not talking about a stock smog motor, but a performance motor.

 

[Eddie]

Thanks I will give it a try.

- - - Updated - - -

Yes the engine will idle high after reving it but if you pull the hose from the vacuum advance it will instantly idle down.

 

[daredevil]

If you have a pcv and no vent its gonna put a vacuum in your block

 

[Eddie]

At this time I do not have a vent.I have to drill out the mopar valve cover and install my factory vent that goes the the breather I guess.Unless you have another idea I can go with.Thanks.Eddie