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PostPosted: Sat Jul 03, 2021 5:28 pm 
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2 BBL ''SuperSix''

Joined: Thu May 27, 2021 2:19 pm
Posts: 15
Location: NW Oregon
Car Model: 1983 B150 (rebuilt 1974 225, 2 bbl)
Unless I've hooked something up wrong, the PCV system of the early slant ('72) is designed to allow the engine to pull in a lot of unfiltered air.

I've routed as follows:
There's a full manifold vacuum (FMV) nipple connected via 3/8" hose to the PCV valve in the valve cover.
The path of least resistance is to draw air through the baffled breather at the other end of the valve cover.
This breather is connected by a 5/8" hose to a nipple on the air filter housing.
The nipple draws air directly through the snorkel, i.e, it's on the perimeter of the housing, outside the air filter.

There's a major amount of vacuum at the PCV opening at idle. So, I'd bet the majority of the air the engine breathes when idling is unfiltered.


Last edited by conrad503 on Sat Jul 03, 2021 5:56 pm, edited 1 time in total.

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PostPosted: Sat Jul 03, 2021 5:44 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
The cap/baffle on the valve cover is actually an old style oil bath air filter..............

Have you cleaned and re-oiled it ever?

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PostPosted: Sat Jul 03, 2021 6:13 pm 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
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Location: Portland-ish
Car Model: Fiat 500e
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This is a filtered breather that fits the 1972 Dodge Dart and many more Chrysler products.

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PostPosted: Sat Jul 03, 2021 9:16 pm 
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Joined: Thu Oct 31, 2002 5:39 pm
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conrad503 wrote:
Unless I've hooked something up wrong, the PCV system of the early slant ('72) is designed to allow the engine to pull in a lot of unfiltered air.


1. The '72 engine isn't really early.
2. There's not much airflow through the PCV system under conditions of high manifold vacuum, such as at idle.

Quote:
There's a major amount of vacuum at the PCV opening at idle


True; the PCV valve will suck your thumb hard, and if all the gaskets and the dipstick tube are intact, your hand will get sucked against the oil cap hole at an idle. That does not mean there's a lot of airflow, it means there's high manifold vacuum.

Quote:
I've routed as follows: There's a full manifold vacuum (FMV) nipple connected via 3/8" hose to the PCV valve in the valve cover. The path of least resistance is to draw air through the baffled breather at the other end of the valve cover. This breather is connected by a 5/8" hose to a nipple on the air filter housing. The nipple draws air directly through the snorkel, i.e, it's on the perimeter of the housing, outside the air filter.


This is the factory configuration. It is correct and should not be altered.

Quote:
So, I'd bet the majority of the air the engine breathes when idling is unfiltered.


Not correct. There's an oil-wetted mesh inside the crankcase breather, and whatever minor amount of dirt makes it past that gets trapped by the engine oil and sequestered in the oil filter.

There is nothing the matter here. Make sure you're using the correct PCV valve and make sure the breather and hoses are in good condition, and you're all set.

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PostPosted: Sat Jul 03, 2021 11:07 pm 
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2 BBL ''SuperSix''

Joined: Thu May 27, 2021 2:19 pm
Posts: 15
Location: NW Oregon
Car Model: 1983 B150 (rebuilt 1974 225, 2 bbl)
Looks just like the breather I've got in place, which is now clean and coated in K&N filter oil.

Thanks for the confirmation of proper routing. The high vacuum vs. airflow distinction makes sense.

The used engine I just installed is in remarkably good condition. Just trying to make sure it stays that way as long as possible.


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PostPosted: Sun Jul 04, 2021 9:26 am 
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If you want to keep the engine in good condition, avoid K&N's fraudulent junk; see here.

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PostPosted: Sun Jul 04, 2021 9:35 pm 
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2 BBL ''SuperSix''

Joined: Thu May 27, 2021 2:19 pm
Posts: 15
Location: NW Oregon
Car Model: 1983 B150 (rebuilt 1974 225, 2 bbl)
Totally agree with that assessment. I no longer run the filters, haven't for years. But I figured, hey, there's a use for that spray can full of filter oil that's been sitting on the shelf collecting dust.


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PostPosted: Mon Jul 05, 2021 7:52 am 
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Turbo Slant 6
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Joined: Sat Sep 13, 2014 8:25 am
Posts: 789
Location: Springtucky OR
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Indeed. K&N oil is good stuff.

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PostPosted: Mon Jul 05, 2021 12:30 pm 
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conrad503 wrote:
filter oil that's been sitting on the shelf collecting dust.

Isn't that exactly what it's meant to do? Collect dust? :mrgreen:

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