PCV process

[AnthonyG]

Probably a dumb question but somebody said even dumber is not asking I had an unrelated issue and no good PCV valve at hand so connected PCV hose direct to vacuum from crankcase and did what I needed. Test drove the vehicle all seemed fine. Couple days later I got a new PCV valve & put it in. The question is why do u need the PCV valve on the crankcase to vacuum tube? Its a one way valve. Is it so not to steal too much vacuum from engine? Don’t beat my ignorance up to bad

[JSeery]

A PCV system is basically a vacuum leak. The PCV valve is to attempt to control that leak under different engine vacuum conditions.

[51 MERC-CT]

The most important function of the PCV valve is to close off any flame path in the event of a carburetor backfire that may detonate the crankcase.

[skidmarks]

Backfire.

I had a 317 ohv Lincoln backfire one time from a timing issue. Blew the oil fill cap off and blew out both valve covers. The 2 studs managed to keep the covers on the motor but you could slip your fingers in passed the gaskets.

[AnthonyG]

Got it! Thx. Hind sight 2020 & makes sense now that I learnt better��

[JSeery]

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There is a lot of info on the internet if you are interested in more detail. If your engine was running fine without the PCV valve in place I would guess there are some A/F ratio issues. That much of a vacuum leak should be noticeable.

[Ggmac]

you must be running very rich , other wise you'd be running like crap , if at all , with unported vacuum .

[David J]

Hope you are not talking about a labyrinth rear seal motor here ?
If yes you may have a mess in the rear of your crankcase .

Originally Posted by AnthonyG

Probably a dumb question but somebody said even dumber is not asking I had an unrelated issue and no good PCV valve at hand so connected PCV hose direct to vacuum from crankcase and did what I needed. Test drove the vehicle all seemed fine. Couple days later I got a new PCV valve & put it in. The question is why do u need the PCV valve on the crankcase to vacuum tube? Its a one way valve. Is it so not to steal too much vacuum from engine? Don’t beat my ignorance up to bad

[34PKUP]

Originally Posted by David J

Hope you are not talking about a labyrinth rear seal motor here ?
If yes you may have a mess in the rear of your crankcase .

When is the last time you have seen an 8BA Flathead Ford equipped with a Labyrinth rear seal?

[David J]

Agreed on the 8BA not having a labyrinth seal .

That said please point out where this post says what type motor is being discussed ?

Originally Posted by AnthonyG

Probably a dumb question but somebody said even dumber is not asking I had an unrelated issue and no good PCV valve at hand so connected PCV hose direct to vacuum from crankcase and did what I needed. Test drove the vehicle all seemed fine. Couple days later I got a new PCV valve & put it in. The question is why do u need the PCV valve on the crankcase to vacuum tube? Its a one way valve. Is it so not to steal too much vacuum from engine? Don’t beat my ignorance up to bad

[blucar]

One of the main purposes of the PCV, ie; the valve therein, is to close under acceleration so there is enough vacuum to operate the vacuum advance in the distributor.

[AnthonyG]

I have an electronic dist w no vac advance. Which is why it doesn’t notice the vac loss I guess. It is an 8BA, sorry should’ve said in 1st post.