DougW wrote:
>
> Mike Romain did pass the time by typing:
> > As someone else mentioned, a plugged up catalytic converter can cause
> > your symptoms. It does happen, the guts can come loose blocking the
> > passages.
> >
> > The only way I know to test for it is to unhook the exhaust before the
> > cat or at the manifold and see if the vacuum comes up.
>
> You can put a pressure gauge in the O2 sensor hole and some of the old
> farts would say, real jeeps don't have catalytic converters. :)
>
> --
> rbg

Up here in Canada, an 86 does not need a cat to pass emissions. Well...
I isn't 'looked' for on the visual test, but if it won't pass, then a
cat might help it....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

 

Any pressure. There is actually a vacuum in the header, and many Hot
Rodders instead of using a positive crankcase ventilation valve that
screws up the fuel mixture, instead use a reed valve (Pulse Air valve)
that works by sensing the drop in manifold vacuum produced by an exhaust
valve closing. Each time the drop in vacuum is noticed, it sucks a
"puff" of crankcase blowby gases into the exhaust pipe.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Will Honea wrote:
>
> Can you put a number on the expected or acceptable back pressure
> (pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
> lots of talk about excessive back pressure, but just what constitutes
> excessive??
>
> --
> Will Honea <whonea@codenet.net>

 

Any pressure. There is actually a vacuum in the header, and many Hot
Rodders instead of using a positive crankcase ventilation valve that
screws up the fuel mixture, instead use a reed valve (Pulse Air valve)
that works by sensing the drop in manifold vacuum produced by an exhaust
valve closing. Each time the drop in vacuum is noticed, it sucks a
"puff" of crankcase blowby gases into the exhaust pipe.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Will Honea wrote:
>
> Can you put a number on the expected or acceptable back pressure
> (pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
> lots of talk about excessive back pressure, but just what constitutes
> excessive??
>
> --
> Will Honea <whonea@codenet.net>

 

Any pressure. There is actually a vacuum in the header, and many Hot
Rodders instead of using a positive crankcase ventilation valve that
screws up the fuel mixture, instead use a reed valve (Pulse Air valve)
that works by sensing the drop in manifold vacuum produced by an exhaust
valve closing. Each time the drop in vacuum is noticed, it sucks a
"puff" of crankcase blowby gases into the exhaust pipe.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Will Honea wrote:
>
> Can you put a number on the expected or acceptable back pressure
> (pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
> lots of talk about excessive back pressure, but just what constitutes
> excessive??
>
> --
> Will Honea <whonea@codenet.net>

 

Now you're making me go out in the cold to look. I'm having
difficulty absorbing the idea that I have a vacuum in both manifolds -
that makes the engine one big sink sucking both ways <g>.

I would suspect that the PCV purge could easily be accomplished into
the exhaust by using the bernoulli effect of the exhaust flow past a
port but I gotta see this vacuum in the pipes. I also would expect
the unburnt vapors would play hell with a cat in short order.

On Tue, 16 Dec 2003 18:54:00 UTC L.W.(ßill) ------ III
<----------@***.net> wrote:

> Any pressure. There is actually a vacuum in the header, and many Hot
> Rodders instead of using a positive crankcase ventilation valve that
> screws up the fuel mixture, instead use a reed valve (Pulse Air valve)
> that works by sensing the drop in manifold vacuum produced by an exhaust
> valve closing. Each time the drop in vacuum is noticed, it sucks a
> "puff" of crankcase blowby gases into the exhaust pipe.
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Will Honea wrote:
> >
> > Can you put a number on the expected or acceptable back pressure
> > (pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
> > lots of talk about excessive back pressure, but just what constitutes
> > excessive??
> >
> > --
> > Will Honea <whonea@codenet.net>


--
Will Honea <whonea@codenet.net>

 

Now you're making me go out in the cold to look. I'm having
difficulty absorbing the idea that I have a vacuum in both manifolds -
that makes the engine one big sink sucking both ways <g>.

I would suspect that the PCV purge could easily be accomplished into
the exhaust by using the bernoulli effect of the exhaust flow past a
port but I gotta see this vacuum in the pipes. I also would expect
the unburnt vapors would play hell with a cat in short order.

On Tue, 16 Dec 2003 18:54:00 UTC L.W.(ßill) ------ III
<----------@***.net> wrote:

> Any pressure. There is actually a vacuum in the header, and many Hot
> Rodders instead of using a positive crankcase ventilation valve that
> screws up the fuel mixture, instead use a reed valve (Pulse Air valve)
> that works by sensing the drop in manifold vacuum produced by an exhaust
> valve closing. Each time the drop in vacuum is noticed, it sucks a
> "puff" of crankcase blowby gases into the exhaust pipe.
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Will Honea wrote:
> >
> > Can you put a number on the expected or acceptable back pressure
> > (pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
> > lots of talk about excessive back pressure, but just what constitutes
> > excessive??
> >
> > --
> > Will Honea <whonea@codenet.net>


--
Will Honea <whonea@codenet.net>

 

Now you're making me go out in the cold to look. I'm having
difficulty absorbing the idea that I have a vacuum in both manifolds -
that makes the engine one big sink sucking both ways <g>.

I would suspect that the PCV purge could easily be accomplished into
the exhaust by using the bernoulli effect of the exhaust flow past a
port but I gotta see this vacuum in the pipes. I also would expect
the unburnt vapors would play hell with a cat in short order.

On Tue, 16 Dec 2003 18:54:00 UTC L.W.(ßill) ------ III
<----------@***.net> wrote:

> Any pressure. There is actually a vacuum in the header, and many Hot
> Rodders instead of using a positive crankcase ventilation valve that
> screws up the fuel mixture, instead use a reed valve (Pulse Air valve)
> that works by sensing the drop in manifold vacuum produced by an exhaust
> valve closing. Each time the drop in vacuum is noticed, it sucks a
> "puff" of crankcase blowby gases into the exhaust pipe.
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Will Honea wrote:
> >
> > Can you put a number on the expected or acceptable back pressure
> > (pressure ahead of the cat) for the 4.0 and/or the 2.5? I've seen
> > lots of talk about excessive back pressure, but just what constitutes
> > excessive??
> >
> > --
> > Will Honea <whonea@codenet.net>


--
Will Honea <whonea@codenet.net>

 

LOL Not many Hot Rodders would choke a '32 roadster with a
catalytic converter.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Will Honea wrote:
>
> Now you're making me go out in the cold to look. I'm having
> difficulty absorbing the idea that I have a vacuum in both manifolds -
> that makes the engine one big sink sucking both ways <g>.
>
> I would suspect that the PCV purge could easily be accomplished into
> the exhaust by using the bernoulli effect of the exhaust flow past a
> port but I gotta see this vacuum in the pipes. I also would expect
> the unburnt vapors would play hell with a cat in short order.
> --
> Will Honea <whonea@codenet.net>

 

LOL Not many Hot Rodders would choke a '32 roadster with a
catalytic converter.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Will Honea wrote:
>
> Now you're making me go out in the cold to look. I'm having
> difficulty absorbing the idea that I have a vacuum in both manifolds -
> that makes the engine one big sink sucking both ways <g>.
>
> I would suspect that the PCV purge could easily be accomplished into
> the exhaust by using the bernoulli effect of the exhaust flow past a
> port but I gotta see this vacuum in the pipes. I also would expect
> the unburnt vapors would play hell with a cat in short order.
> --
> Will Honea <whonea@codenet.net>

 

LOL Not many Hot Rodders would choke a '32 roadster with a
catalytic converter.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Will Honea wrote:
>
> Now you're making me go out in the cold to look. I'm having
> difficulty absorbing the idea that I have a vacuum in both manifolds -
> that makes the engine one big sink sucking both ways <g>.
>
> I would suspect that the PCV purge could easily be accomplished into
> the exhaust by using the bernoulli effect of the exhaust flow past a
> port but I gotta see this vacuum in the pipes. I also would expect
> the unburnt vapors would play hell with a cat in short order.
> --
> Will Honea <whonea@codenet.net>