PCV valve hose goes???

[RJRENTON]

Interesting…. An engine builder friend indicated the PCV should be connected to manifold vacuum and not carburetor?
I believe there’s a plug on the throttle body front base….

And the difference is....?????.....(the same).....
BOB RENTON

 

[koosh]

And the difference is....?????.....(the same).....
BOB RENTON

I don’t know…. Hence my thread.
Thought manifold vacuum and carb vacuum were 2 different things….
Manifold and ported vacuum, what’s that?

 

[RJRENTON]

I don’t know…. Hence my thread.
Thought manifold vacuum and carb vacuum were 2 different things….
Manifold and ported vacuum, what’s that?

NO.....ITS THE SAME......like asking how high is up....or why is there air......vacuum is the absence of air.....you could run a hose to the moon for some serious vacuum........
BOB RENTON

 

[BLK 68 R/T]

100% WRONG ANSWER....the carb is calibrated to have PCV introduced into the idle mixture below the throttle plates to smooth out and dilute the mixture. An added benefit is PCV helps to remove condensate as moisture from the engine internals and to assist in removing blow-by products and keeps the oil cleaner. Just about ever vehicle made from mid 1960's is equipped with PCV system. What don't you understand about the PVCs function??? The carb has a PCV CONNECTION on its base flange....the FSM shows how it works and identifies it's function.......
BOB RENTON

But the op has efi, not a carb.

 

[RJRENTON]

But the op has efi, not a carb.

The vacuum connection should be on the BACKSIDE (negative pressure side) of the EFI's main butterfly valve, which controls the air flow thru the system. Usually, the air flow METERING DEVICE (a hot wire sensor or pitot array reading differential pressure), is upstream of the butterfly valve in a less turbulent area. Usually on a EFI system, the MAP (Manifold Absolute Pressure) sensor monitors down stream vacuum. A MAP sensor is opposite to Manifold vacuum........
BOB RENTON
,

 

[zombezoo]

The vacuum connection should be on the BACKSIDE (negative pressure side) of the EFI's main butterfly valve, which controls the air flow thru the system. Usually, the air flow METERING DEVICE (a hot wire sensor or pitot array reading differential pressure), is upstream of the butterfly valve in a less turbulent area. Usually on a EFI system, the MAP (Manifold Absolute Pressure) sensor monitors down stream vacuum. A MAP sensor is opposite to Manifold vacuum........
BOB RENTON
,

And you want the hose plumbed to the carb base rather than a port to a specific set of runners in the manifold to spread any oily residue across all cylinders rather than dose 1-2 of them.

 

[koosh]

And you want the hose plumbed to the carb base rather than a port to a specific set of runners in the manifold to spread any oily residue across all cylinders rather than dose 1-2 of them.

So you’re saying plumb to the carb base (front or rear?) rather than to a fitting on the manifold?

 

[zombezoo]

So you’re saying plumb to the carb base (front or rear?) rather than to a fitting on the manifold?

You will need to refer to your EFI instructions, my Fitech installation manual (see photo) suggested using one port vs another for PCV vs Brake Booster but the takeaway I had was that the carb base spreads the oil residue across all cylinders and should be used over a port in the intake that feeds vapor to only 1 or 2 of the cylinders. Ultimately you will need to look at the specific parts you have to determine how they are configured.

 

[coloradodave]

Both my FiTech EFI and my Holley Sniper EFI have 3/8" hose connectors for PCV or brake booster use...PCV valve typically goes on one valve cover and a vented breather cap goes on the other. Fresh air is drawn into the crankcase of the engine through the vented breather and ends up in the intake manifold via the PCV valve and engine vacuum. A side benefit is that the top of the engine stays much cleaner.

 

[BLK 68 R/T]

I have the first version of the ez-efi on my car. Vacuum headlight doors, power brakes and vacuum advance all hooked up. No pcv, just breathers in both valve covers. No issues.

 

[RJRENTON]

Both my FiTech EFI and my Holley Sniper EFI have 3/8" hose connectors for PCV or brake booster use...PCV valve typically goes on one valve cover and a vented breather cap goes on the other. Fresh air is drawn into the crankcase of the engine through the vented breather and ends up in the intake manifold via the PCV valve and engine vacuum. A side benefit is that the top of the engine stays much cleaner.

I'm not really familiar with both EFI systems you noted. They appear to be TBI (Throttle Body Injection) systems.....adaptations of a GM TBI system used in their middle 70s economy vehicles (Pontiac 6000 4 cylinder engine, etc), rather than a more traditional fuel Injection systems....multi point (all injectors pulsed on simultaneously at 1/N where N = number of cylinders of the engine), sequential port injection system sequence, where the injection program precedes the ignition sequence both were used by Ford, and GM and directed the fuel intake charge behind the intake valve. IMO.....a TBI SYSTEM is not a true fuel Injection system as the fuel charge is delivered via an intake manifold (identical to a carb delivery system) not directly to the intake port, immediately b4 the intake valve opens. .......perhaps someone can enlighten me.......I'm mot to old to learn....... just my thoughts....
BOB RENTON.

 

[BLK 68 R/T]

I'm not really familiar with both EFI systems you noted. They appear to be TBI (Throttle Body Injection) systems.....adaptations of a GM TBI system used in their middle 70s economy vehicles (Pontiac 6000 4 cylinder engine, etc), rather than a more traditional fuel Injection systems....multi point (all injectors pulsed on simultaneously at 1/N where N = number of cylinders of the engine), sequential port injection system sequence, where the injection program precedes the ignition sequence both were used by Ford, and GM and directed the fuel intake charge behind the intake valve. IMO.....a TBI SYSTEM is not a true fuel Injection system as the fuel charge is delivered via an intake manifold (identical to a carb delivery system) not directly to the intake port, immediately b4 the intake valve opens. .......perhaps someone can enlighten me.......I'm mot to old to learn....... just my thoughts....
BOB RENTON.

Yes, you are correct. They are throttle body injection systems. They do utilize an O2 sensor in one exhaust pipe. There are true fuel injection systems available but the majority of the systems are of the throttle body injection type.

 

[1967coronet]

Koosh, On street engine run with a pcv. Hook to 3/8 un Ported vacuum, front or back but below the blades.
You need a breather in the other valve cover for inbound air flow. This will help with internal pressure and help prevent oil leaks.

 

[68 Sport Satellite]

I run a carb, but have one of the caps with built-in PCV valves installed on one of the valve covers. Not just a breather cap, but with a built-in PCV valve. Not sure if this is a good option or not...

 

[68 Sport Satellite]

You need a breather in the other valve cover for inbound air flow. This will help with internal pressure and help prevent oil leaks.

can you expand on this a bit more? What if it's a breather cap that has a PCV valve built-in installed on one valve cover? Any need to separate the 2?

 

[RemCharger]

 

[eldubb440]

can you expand on this a bit more? What if it's a breather cap that has a PCV valve built-in installed on one valve cover? Any need to separate the 2?

air normally gets sucked through a breather on one side and circulates across to the pcv on the other side; IE left front to right rear

sort of unrelated, but AMC's work front to back........ but same principal, they need to be apart from each other

 

[eldubb440]

when functioning properly, on a healthy engine with no blowby; you should be able to stick a dollar bill to the breather side hole (suction)

 

[1967coronet]

can you expand on this a bit more? What if it's a breather cap that has a PCV valve built-in installed on one valve cover? Any need to separate the 2?

Like rem & dubb posted,
Air in and air out , keeps internal pressure low.

 

[not so famous bob]

I

I gotta tell ya….. you thoroughly lost me at:
“with an EFI you should run a fixed orifice (basically a gutted pcv filled with epoxy and drilled to a specific size.) Reason being if the pcv fails open, efi will correct the a/f imballance with more fuel = engine revs.”
Ive not run this motor yet (only on test stand with carburetor)
Was not sure to run a hose to throttle body base, or the intake somewhere if i can find a port on this Edelbroch Torker 440

have the vacuum hose hooked to both nipples on my fast fuel inj. system , control the vacuum with a small temporary valve .
sure helps with oil leaks...both are manifold vacuum , exhaust evac on drivers side ...