Draft Tube ventilation.

[Noah H]

My buddy’s car had about a foot of steel wool stuffed in the draft tube. 

found it while I was degreasing his engine. 
 

is this a big no-no? 
 

 

[greg g]

OK for keeping critters  out, not so good for letting fumes and moisture out.  I have a piece of kurly Kate scrubbing pad in mine. Also known as a chore boy..

 

[Noah H]

57 minutes ago, greg g said:

OK for keeping critters  out, not so good for letting fumes and moisture out.  I have a piece of kurly Kate scrubbing pad in mine. Also known as a chore boy..

 

I drive the car regularly, do I really need to put something in there? I guess it may be a matter of opinion. 

[JBNeal]

a PCV upgrade could be beneficial...

 

additional information - PCV installation

[Loren]

One of the benefits of a PCV is that it puts the crankcase under vacuum.

Part of the combustion products are water vapor.

When you put the crankcase under vacuum it de-hydrates the gases and by doing so it keeps the engine free of sludge.

There is one thing to remember, if your engine already has lots of blow by a PCV system might not have enough vacuum to accommodate it.

The hose to the air cleaner does two things, provides make up air for that which the PCV has sucked out (creating a draft) and providing an outlet for excessive blow by.

My Dad tended to drive cars into the ground and when the law required a retrofit PCV in California, the blow by was such that the rear main seal started leaking like mad.

So the rule is check the blow by before you install one. If it's not bad then go ahead.

A PCV is the one smog device which actually has some benefits to the engine.

[Bryan]

5 hours ago, Loren said:

One of the benefits of a PCV is that it puts the crankcase under vacuum.

A PCV is the one smog device which actually has some benefits to the engine.

Just a matter of how to go about it. I'm not impressed with the Power Wagon $85 system.  Fitting out of round and loose..PCV valve doesn't seal completely one way, smart aleck sales guy.  The special fitting hole is the same as a freeze plug..one could almost have threaded a hose fitting in a plug and tapped it into the hole with a little sealant on it.

[Bryan]

7 hours ago, JBNeal said:

a PCV upgrade could be beneficial...

 

additional information - PCV installation

Like your DIY system better..

[Sniper]

Running a hotter thermostat also helps drive moisture out of the crankcase.

[38plymouth]

A pcv system also adds a vacuum leak to your system. I struggled with running lean for years and finally yanked the pcv off and the car has never run better. I guess if you had the right carb and jets you could make it work, it sure didn't like my stock b&b.

[Loren]

In the downloads section there are instructions and drawings of the factory PCV kit.

It does talk about carburetor parts that need to be changed on the B & B carburetor.

 

One thing that caught my eye and started me thinking was the difference in air cleaners.

P17s have a nice looking Oil Bath that has no "Silencing Chamber." While the Special Deluxe had a big clunky Oil Bath that did.

I always remembered my P18 was much quieter than the P17 I have now. Now I know the reason or at least one of the reasons.

So on my next trip to my storage I am going to dig out my collection of air cleaners and do some experimentation.

If it isn't a fire breathing race car, it might as well be quiet.

[Bryan]

I haven't done it for a while, but am I correct that a PCV valve should act almost like a check valve?   Sucking on one end closes it tight, sucking on other end flows free?  The one from VPW acts differently.

[Sniper]

the PCV acts as a check valve in case of a backfire, not sure you can blow that hard, lol.  Any other time there is some flow.

[38plymouth]

If I remember correctly, its closed at high vacuum during idle then opens when at Cruise and low vacuum. It creates a lean condition off idle if you don't adjust the carb for it.

[Sniper]

Modern PCV's are definitely not closed at idle, just limits the flow though.  Not sure about the factory setup though.  

 

[kencombs]

They don't all act exactly the same.  They have always been tailored to the specific engine.  Some are, for all practical purposes closed at idle, most of the flow at that point is just because they don't seal tightly.    Non-stock cams can really mess with the operation of a factory PCV system as the vacuum is nothing like the original design.

[Bryan]

On 11/26/2021 at 1:36 AM, Loren said:

One of the benefits of a PCV is that it puts the crankcase under vacuum.

Part of the combustion products are water vapor.

When you put the crankcase under vacuum it de-hydrates the gases and by doing so it keeps the engine free of sludge.

There is one thing to remember, if your engine already has lots of blow by a PCV system might not have enough vacuum to accommodate it.

The hose to the air cleaner does two things, provides make up air for that which the PCV has sucked out (creating a draft) and providing an outlet for excessive blow by.

 

From what I remember from my 71 Camaro it was a system like in the picture (but a V8). For our flat 6 engines you would think a good filter on the breather cap next to the dip stick would do the trick.  We don't have overhead valve covers..

[Bryan]

Edited November 28, 2021 by Bryan
Trying to add text..look at the oil breather

[Adam H P15 D30]

You can build your own PCV system for a few bucks...

[Loren]

4 hours ago, Adam H P15 D30 said:

You can build your own PCV system for a few bucks...

 

I think you're on to something!

The PCV valve you are using is "All or Nothing" its purpose is to prevent intake backfires from popping seals and gaskets.

The factory (or at least the one VPW sells) has a constant vacuum draw and the backfire prevention.

I can't imagine there's any more benefit to the VPW item.

One thing that recommends your solution is that it will clear an aluminum valve chamber cover.

My 49 P17 has a large round chamber where the road draft tube goes into the block with a filter in it.

I haven't been able to find that in my parts manual but I have seen them before.

That type would be the ideal one to modify. I seem to recall that the retro fit items used that design back in the day.

[Loren]

Here's a photo of the filter type

[Adam H P15 D30]

2 hours ago, Loren said:

 

I think you're on to something!

The PCV valve you are using is "All or Nothing" its purpose is to prevent intake backfires from popping seals and gaskets.

The factory (or at least the one VPW sells) has a constant vacuum draw and the backfire prevention.

I can't imagine there's any more benefit to the VPW item.

One thing that recommends your solution is that it will clear an aluminum valve chamber cover.

My 49 P17 has a large round chamber where the road draft tube goes into the block with a filter in it.

I haven't been able to find that in my parts manual but I have seen them before.

That type would be the ideal one to modify. I seem to recall that the retro fit items used that design back in the day.

Not quite sure what you mean by "all or nothing" but this PCV I am using has a metered orfice (like all PCV valves) and a constant flow provided there is manifold vacuum.

I just cut my draft tube off and rotated it 180 degrees.  I think you could do the same with the one you show above.

Edited November 29, 2021 by Adam H P15 D30

[Loren]

30 minutes ago, Adam H P15 D30 said:

Not quite sure what you mean by "all or nothing" but this PCV I am using has a metered orfice (like all PCV valves) and a constant flow provided there is manifold vacuum.

I just cut my draft tube off and rotated it 180 degrees.  I think you could do the same with the one you show above.

 

"All or Nothing" is meant to mean it either flows or it doesn't.

Do you remember what the PCV valve you used came off of?

I have a VPW valve (for use on another engine) and it might be of value to compare them.

Thanks for sharing!

[Adam H P15 D30]

It always flows through it's orfice as long as there is manifold vacuum and not backfiring.  I am almost positive the application is GM 2.8L V6, the rubber gromet I found in a box store's help section so I do not know the application.

 

EDIT: Maybe 3.8L, it's been a few years

Edited November 30, 2021 by Adam H P15 D30