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Old 03-09-2007, 07:47 PM
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carb is whistling

i just removed my PCV valve from from vavle cover to the carb. and the carb is starting to whistle. i removed it because i was suckin oil through the valve. what can i do to get rid of the whistle??? or should i put the pVC valve back on and deal with the oil???

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Old 03-09-2007, 07:55 PM
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Did you remove the sheet metal baffling inside the valve cover?
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Old 03-09-2007, 08:24 PM
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Quote:
Originally Posted by elcaminodragster
i just removed my PCV valve from from vavle cover to the carb. and the carb is starting to whistle. i removed it because i was suckin oil through the valve. what can i do to get rid of the whistle??? or should i put the pVC valve back on and deal with the oil???
If your PCV is sucking oil, you need to deal with that issue instead of just removing the valve.

Sounds to me like you need to do some diagnostics on the engine to determine exacly why it is doing this.

All a PCV does is ventilate the crankcase to remove pressure build-up, you must have something pressurizing the crankcase causing the oil issue.
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Old 03-10-2007, 01:31 AM
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Quote:
Originally Posted by techinspector1
Did you remove the sheet metal baffling inside the valve cover?

no it is still in there. and they are tall covers to.
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Old 03-10-2007, 01:37 AM
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i have 2 breathers one for each side.
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Old 03-10-2007, 02:06 AM
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carb is whistling

When you pulled the PVC valve did you put a plug in the line? If not you created a vacuum leak. Thus a whistle.

Why is the PVC sucking oil? The PVC is working because it has vacuum to it. Air has to get into the engine through some place. Is the filter clean? Most engines, there is a filter in the air cleaner, a hose goes to the valve cover on the opposite side on a V8 , or to to rear on a 6 cyl. The same applies air in fumes out.

When you pulled the PVC out with the engine running is there a lot of oil fumes coming out the hole (Valve cover)? If so that is what has to be addressed. Why the excessive fumes. High mileage, bad rings, valve seals, oil drain holes clogged in the head.

Hope this gives you a starting point. russ
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Old 03-10-2007, 10:20 AM
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Quote:
Originally Posted by russlaferrera
When you pulled the PVC valve did you put a plug in the line? If not you created a vacuum leak. Thus a whistle.

Why is the PVC sucking oil? The PVC is working because it has vacuum to it. Air has to get into the engine through some place. Is the filter clean? Most engines, there is a filter in the air cleaner, a hose goes to the valve cover on the opposite side on a V8 , or to to rear on a 6 cyl. The same applies air in fumes out.

When you pulled the PVC out with the engine running is there a lot of oil fumes coming out the hole (Valve cover)? If so that is what has to be addressed. Why the excessive fumes. High mileage, bad rings, valve seals, oil drain holes clogged in the head.

Hope this gives you a starting point. russ

yes i made sure i pluged it.

not sure why its sucking oil... but its doing it so bad that the valve when i last pulled it was dripping oil outta it.

no fumes come out. when i changed the valve covers from short to tall covers... i looked really good to make sure the heads were in good condi. the drain plugs are good.

my bud told me i might have to much carb vac???? is that possible or any where near true????
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Old 03-10-2007, 12:53 PM
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Typically, a problem like this is the result of either a plugged ventilation system or an engine issue that is introducing pressure into the crankcase, such as excessive cylinder blowby.

The system needs to be hooked up to a manifold vacuum source, is that where you have it?

I would run a cylinder leakdown test if you are truly sure you don't have a blockage in the system somewhere.
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Old 03-10-2007, 01:48 PM
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Quote:
Originally Posted by Lonestar
Typically, a problem like this is the result of either a plugged ventilation system or an engine issue that is introducing pressure into the crankcase, such as excessive cylinder blowby.

The system needs to be hooked up to a manifold vacuum source, is that where you have it?

I would run a cylinder leakdown test if you are truly sure you don't have a blockage in the system somewhere.

i had it hooked up to the center port on my avs 650 edelbrock. it dosent say its manifold vac but i belive it is. it says its a pvc port. im most positive i dont have a blockage. i dont have any of that testing equepment. would a shop have that stuff??? about how much would it run??? (ball park the price)
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Old 03-10-2007, 03:04 PM
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carb is whistling

Did you have this problem with the short valve covers? Carb whistle sound is coming from? Base gasket, where?

Is it possible, that the shield in the valve cover is not large enough to protect the PCV from oil spray off valve train?

With the engine running and PCV in place are you getting any air into the engine from the other valve cover that has the breather?
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Old 03-11-2007, 12:04 PM
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Quote:
Originally Posted by russlaferrera
Did you have this problem with the short valve covers? Carb whistle sound is coming from? Base gasket, where?

Is it possible, that the shield in the valve cover is not large enough to protect the PCV from oil spray off valve train?

With the engine running and PCV in place are you getting any air into the engine from the other valve cover that has the breather?

yes i had the same prob with the short covers. the sound is coming from inside the carb. im not sure if its protected enought ill check that out. but just lookin at it with the covers on it looks very protected.

ill have to see if i am getting air into the other breather i belive i am coz i had to replace it awhile back coz it was getting dirty. so i belive i am but ill dubble check
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Old 11-06-2007, 05:31 AM
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whistle

I use a Edelbrock 750 Performer on a well prepared 383 which tends to whistle at idle. I'm still running the engine in and finishing other stuff off on the car, but when I get the time I will chase the whistle.

I rebuilt the carb completely only a few days ago and IDed a few areas that I thought might whistle. One is the penetration at the front where the PCV connects to. If the PCV is blocked then the passage for it will be a constant low pressure zone as the airflow go past the hole for it and might cause a whistle, plus that is where the idle air will tend to flow pass. Another is the screws that fix the throttle plates to the main shaft. They tend to be well over length and thus project a fair way out the other side of the shaft and so could cause a bit of turbulence.

Another reason could be a vac leak of course. That's possible, but I paid particular attention to sealing as I put it together so I don't think it likely.
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Old 11-06-2007, 08:46 AM
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camino,

breathers on both covers and a pcv...defeats the purpose of the pcv valve....by having one or two breathers on one cover only and pcv only on the other cover it draws and sucks the air all the way thru the block....fix that first...not only gets the bad stuff out but helps cool the rotating assembly
(on your motor, with a breather and pcv on one cover, you are just sucking in air from the breather on the same cover to the pcv, not thru the motor at all)

your friend is correct kind of,, a wrong size hole (to small) and weight pcv valve for the motor vacuum can dramatically increase the air velocity/suction power at the pcv valve opening.....
(think of a 2" vacuum cleaner hose necked down to a 1/2" hose attachment works)
a $3 pcv valve with a "bigger hole" will likely help, they usually have a heavier weight which helps seal it when you go WOT

if you are positive the drainback holes are clear......and your oil pressure is normal cruisin'.....fair chance the baffle need improvement and/or the pcv valve needs to be higher, away from the baffle

dumb...... but many aftermarket covers have the cover hole directly aligned with a pushrod end so it is squirting the oil directly at the pcv and the baffle becomes a "shelf" for the pcv to suck oil from if it is to close

to raise the pcv valve away from the baffle....a short piece of heater hose works fine...see pic'

to answer "how much oil is actually being picked up by the pcv", make something similar to the pic attached out of a plastic lid jar to act as a "accumulator"....it's just a hose and fitting screwed into the lid from the pcv and a fitting and hose out of the lid to the carb pcv....very helpful to be able to tell if the changes to the baffle etc are actually helping (that's a $10 air compressor filter with the filter drilled out so it can't clog in the pic'...peanut butter jar is just as good)

to cure the 60psi oil pressure and 18Hg motor in the pic' took about 5 trys with different shapes and sizes of baffles...basically the baffle is tight to the cover high side at the intake and extends almost to the low side cover curve and is only open a tiny bit....from memory, it was about 4"x4" with <1/8" open along the lower edge and closed on the ends
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