[Shotimes] What can destroy a cat?

Fri, 18 Jun 2004 12:00:39 -0400

Dave,

Thanks for the tip.  How is the test actually done?  I assume the car isn't running since the only place to measure the pressure would be at the sparkplug which means the manifold is off. Do I crank it manually or do I crank with the key/battery (in which case I should probably disconnect all the plug wires, right?)  

Btw, if you have a problem with bad valve stem seals (Is this the same as valve guides?), firstly, how do you know this? And secondly, aren't you concerned about it? 

Btw, btw, don't all SHO's smoke as hell when you're on the throttle and between shifts?  Mine has always done this, I think, cause every time I do it, I can actually see the smoke in the rearview mirror.

Michael Olsen
94MTX,green,BOS+
----- Original Message -----
From: DAVE <cobraii976@sbcglobal.net>
Date: Friday, June 18, 2004 11:31 am
Subject: Re: RE: [Shotimes] What can destroy a cat?

> The best way to test the ring theory is to do two compression 
> tests. One dry and one wet. Do all the cylinders and record the 
> PSI. just a generic example is 5 of the cylinders are at 150 psi 
> and one is at 120 PSI. Then do them all again with a 2-3 squirts 
> of oil down the cylinder from an oil can. Squirt on cylinder at a 
> time. the first 5 should stay in the same range of the 150. The 
> one down to the 120 will bump up considerbly say to 150. Like I 
> said this is a generic example and not actual SHO figures. What 
> happens is if your getting enough blow by to lose compression your 
> burning oil at the rings when the oil is added on top of the 
> piston your getting it before blow by.
> Then again you could just have the same problem I'm having. Bad 
> valve stem seals. I don't puff on start up and I don't puff any 
> oil at all.........Unless I'm into the throttle and between 
> shifts........Then I smoke big as hell........
> Dave
> 
> cmichaelo@optonline.net wrote:
> Considering the car is 10y old, has 130k on it, I'm using Amsoil 
> and that I don't race my car, is it still likely that a piston 
> ring can wear down this fast?
> 
> ----- Original Message -----
> From: Leigh Smith 
> Date: Thursday, June 17, 2004 4:31 pm
> Subject: Re: RE: [Shotimes] What can destroy a cat?
> 
> > What he said. As a ring wears, it may still seal well, but the 
> gap 
> > grows,and you get more blow-by.
> > There is such a thing as a gapless ring, for those racers 
> looking 
> > for almost
> > zero percent leak-down.
> > No clue whether there is a version for our SHOs.
> > Lee
> > 
> > , a failing piston ring will result
> > > in oil being burned in the combustion chamber which
> > > may be closer to what you have happening in your car.
> > >
> > > Ian
> > > --- cmichaelo@optonline.net wrote:
> > > > I've heard about oil leaking into the cylinders
> > > > through the valve guides, but supposedly that should
> > > > generate a blue puff of smoke when I start the car,
> > > > and that I don't see. So I can imagine that perhaps
> > > > oil is entering the cylinder through the cylinder
> > > > walls or due to a broken cylinder head gasket.
> > > >
> > > > Which one is more likely, and are there other ways
> > > > oil can enter the cylinders?
> > > >
> > > > Michael Olsen
> > > > 94MTX,green,BOS+,130k
> > > >
> > > > ----- Original Message -----
> > > > From: Bill Murray 
> > > > Date: Tuesday, June 15, 2004 12:32 pm
> > > > Subject: RE: [Shotimes] What can destroy a cat?
> > > >
> > > > > Burning oil will also cause cats to go bad. They
> > > > are not designed to
> > > > > burnoff the extra "stuff" that the exhaust will
> > > > have in it.
> > > > >
> > > > > Bill Murray
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: cmichaelo@optonline.net
> > > > [cmichaelo@optonline.net]
> > > > > > Sent: Tuesday, June 15, 2004 11:20 AM
> > > > > > To: shotimes
> > > > > > Subject: [Shotimes] What can destroy a cat?
> > > > > >
> > > > > >
> > > > > > I have now destroyed my second catalytic
> > > > converter. I'm
> > > > > > trying to find out if something is wrong my
> > > > engine, or if the
> > > > > > cats were just of poor quality to begin with.
> > > > > >
> > > > > > Both cats were bought from Sho Shop in 1997.
> > > > > >
> > > > > > The first cat lasted about 40k, and the second
> > > > about 30k.
> > > > > >
> > > > > > I strongly suspect that the first cat died to
> > > > some prolonged
> > > > > > trouble with the MAF which produced rich fuel
> > > > mixture. During
> > > > > > the life of the first cat I only averaged 17-18
> > > > mpg.
> > > > > >
> > > > > > But with the second cat I had no such problem
> > > > with the MAF.
> > > > > > I'm now averaging 20-21 mpg. However, I do have
> > > > an excessive
> > > > > > oil consumption, and I'm wondering if oil is
> > > > leaking into the
> > > > > > cylinders and is burning up, if that can destroy
> > > > a cat?
> > > > > >
> > > > > > What else could destroy a cat? I have 130k on
> > > > the car. New
> > > > > > oxygen sensors. New 77mm ProFlow MAF. No chip.
> > > > Good
> > > > > > acceleration. Good idle. Car is due for 60k
> > > > though.
> > > > > >
> > > > > > Michael Olsen
> > > > > > 94MTX,green,BOX+
> > > > > >
> > >
> > >
> > >
> > >
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