PCV Valve or Breather Filter?

[Wbruiser2]

I had an off idle stumble and have three or four posts about it but finally figured out it was the PCV valve connection. It was connected to the intake. When I removed it and hooked up the vacuumn gage it idled and rev'd as smooth as can be. I don't why the PCV valve was causing this issue since it seems to be fairly new. From what I have read, shouldn't it be hooked to the back of the carb? The brake booster is hooked there now. I would switch it but the line isn't long enough so I have to get some more. I know what the PCV does but does anyone just run a breather filter in the valve cover and not have any issues? I figure my options are replace the PCV valve and hope it was at fault and or switch the connection with the booster, or run a breather filter. All of them require me to go to AZ and get something. This truck is not a daily driver. Anyone have and similiar issues/ resolutions? Thanks

 

[DNFXDLI]

Does the pcv valve rattle?
You can just "T" into that line. If the pcv valve is faulty, it can create a vacuum leak.

 

[Mil1ion]

What type and year engine ?

On the 78 400 the PCV went into the right valve cover wile the left side valve cover has a hose on the oil cap

 

[SuperCab]

You're going to need a PCV valve... without it moisture can build up in the engine... A breather doesn't pull moisture/combustion gasses/other vaporous crap out of the crankcase.

 

[Wbruiser2]

It's a reman 302(from advance auto) bored .30 over put in about 3 years ago (according to the po).
The PCV valve is causing the off idle stumble whether its connected to the intake or carb. It free flows out and it does rattle. Unless there is a PCV valve that gradually opens under vacuum and pressure I guess I'm going to have to get creative

 

[Mil1ion]

Intake sucks the fumes thru the pcv valve from the crankcase
The other valve cover hole should be sealed with the oil cap

 

[blacksnapon]

I've had one (yes, 1) that was running rich so bad that there was fuel in the oil pan. That caused excessive fuel vapors in the crankcase. The pcv was picking it up, not allowing it to run correctly. Pull the pcv, it smoothed out. Just be aware of underlying causes.

 

[Wbruiser2]

Let me clarify my PCV valve issue I'm having and what I know:
I realize the engine needs to breath. On mine, I have a breather/oil cap that takes in fresh air from the hose running to/from the air filter. The PCV (in the passenger side valve cover) is suppose to be hooked to a vacuum port and sucks all the contaminants/fumes out which is sucked back in to the carb/intake to be burned and also prevents pressure from building up that will blow gaskets and seals.
My problem is, my PCV valve is a huge vacuum leak and is causing an off idle stumble and causes the truck to run like **** when cruising. The PCV valve that I have rattles and free flows out. So I guess my question is, since it free flows out do I really need it hooked to a vacuum source or do I have a bad or the wrong one? The way I see it, by not having it connected to vacuum, it won't build pressure, I may have to change the oil a little more often, and I get rid of the stumble. I think I need to experiment with some other PCV valves that open under pressure if thats even an option... If you have had a similiar issue I would like to hear how you resolved it.

 

[SuperCab]

I would say replac the PCV valve (they're cheap) and make sure that vacuum hose going to it has no leaks... Aside from that you have an underlying issue. It's tempting to leave the PCV off and drive it but that won't fix whatever the problem really is.

Off idle stumble... do you think it's too rich or too lean that's causing it? The fact that taking the PCV off fixes it makes me think you're too lean? For those of us who don't remember (me) what kind of carburetor are you running?

 

[Wbruiser2]

Off idle stumble... do you think it's too rich or too lean that's causing it? The fact that taking the PCV off fixes it makes me think you're too lean? For those of us who don't remember (me) what kind of carburetor are you running?[/QUOTE]

The Carb is a 570 Holley. I think the carb is set right. I've adjusted the accelerator pump, float bowls, and idle mixture screws. I don't have any other issues except this stumble and if I richen it up it doesn't go away, I just smell the fumes. It's got a .31 squirter and I don't know what size jets it has. I used to think the squirter was the culprit. I was missing the washer between the screw and squirter so I ordered a new squirter that came with washers. I accidentally cut one opening the pack so I reused the bottom one. Now you have me thinking. The bottom one was metal and the new ones were paper like. Maybe the bottom isn't sealing like it should and is preventing a good squirt... lol I said squirt. I'll have to check that out again. That very well could cause the lean condition at and off idle. Thanks for your input.

 

[SuperCab]

Let us know what you come up with

 

[Mil1ion]

The accelerator rod has to be indexed to the correct hole on the lever..normally it is position 2 or 3 .
What is yours set up?
Do you have an egr valve on it?

 

[Wbruiser2]

The accelerator rod has to be indexed to the correct hole on the lever..normally it is position 2 or 3 .
What is yours set up?
Do you have an egr valve on it?

As far as I know I don't have an accelerator rod. Just the diaphram, pump arm, spring, lever, and cam which is adjustable. I have the orange one and I have tried settings one and two but left it on one. I don't have an egr valve. The only things hooked to vacuum other than the PCV is the Booster, transmission, and vacuum advance. The two front bottom ports on the carb are capped off, the rear carb port is connected to the booster, and the PCV valve was connected to the rear intake. I still need to find some of those dag gum washers and I don't mean a pack of ten for $10+ ...

 

[Mil1ion]

The vacuum supply for the poster should run directly to the intake NOT TO THE
CARB

The transmission also goes to the vacuum tree withe booster

The vacuum to the dizzy should be acquired from the ported nipple in front of the Carb

The PVC hose should run to the back the Carb at the egr plate


Photos would help. Detailed photos

 

[Wbruiser2]

Just a follow up: I do believe I have gotten rid of the off-idle stumble by routing the pcv valve to the front port of the Carb that Holley says is the PCV port and plugged the rear port. Initially I didn't have a timing pointer so I made one, set the #1 cyl at TDC, and wrapped the balancer with new timing tape with 0 at the pointer. I set the timing at 8degrees and it sounded fine up until about 1800+ RPM then it started missing bad. So I just reved it up until it started missing and retarded the timing until it quit. Still idles and revs good. Checked the timing and it about 4 degrees ATC... I think my helper was a little off on the TDC. Still waiting(3 weeks now) on my seat cover so I can reassemble, install it and go for a drive.

 

[Mil1ion]

Please detail the condition of your distributer

They are subject to wear and V/A's seizing or tearing causing timing and performance issues

 

[Wbruiser2]

TDC was off by about 10 degrees so now its set at 12 degrees and runs great. Well it did anyway. I took it out on the road and was just cruising around and it was so smooth. Then I stopped and floored it till I got to around 80mph and then it started missing and cutting out after I let up and started to cruise again. I get home and raise the hood and I have no fuel pressure at the gauge and I can see an air bubble in the fuel filter. I checked the fuel line all the way back and I assume the rubber line going from the metal to the tank is bad, it was really soft and spongy like and looked orginal...

 

[Mil1ion]

Replace any rubber line with steel if you can. Sounds like it is sucking air THROUGH the old rubber. Check your V/A and the dist shaft for untrue spinning.