[Shotimes] Rod Bearing Change @190K miles

[cmichaelo@optonline.net]

I changed the rod bearings on my 94 MTX at 125k miles....and boy am I glad I did.

Here's how much (%) Copper was showing:

Cylinder            #1   #2   #3   #4   #5   #6
Upper bearing   66   90   50   15   10   40
Lower bearing    0   90     0     0    10   10
			
There seems to be a problem in cylinder #2.  This cylinder also showed chared spark plug. The others didn't.  I also have high oil consumption - 500 miles/qt.  

I'm suspecting either a scratch in the cylinder wall or broken piston ring.  I've had two cats fail on the car, so this has probably something to do with it.

To deal with this temporary, I'm doing the Auto-Rx treatment.

I plan to take the pistons out soon  to inspect. Wanna replace them with high compression forged pistons.

Michael
94MTX,green,BOS+,Koni/Intrax,Baer,Corbeau
SHO items for sale: http://hometown.aol.com/cmichaelo/for_sale.html

----- Original Message -----
From: Donald Mallinson <dmall@mwonline.net>
Date: Tuesday, January 31, 2006 11:26 am
Subject: Re: [Shotimes] Rod Bearing Change @190K miles

> I would agree with the lugging theory, sounds good.
> 
> I just replaced the bearings in my '89 with 180,000 miles, and 
> only the 
> top ones showed any real wear, a small 3/4" oval still in the 
> silver/grey material.   the car had Valvoline 10-30 for the first 
> 45,000 
> miles and Synthetic (mostly Amsoil 0-30 or 5-30) for the rest of 
> its 
> life.  Ran the 0-30 for 25,000 miles between changes for a few 
> years.  
> So much for having to change every 3000 miles!   :)   The car got 
> puit 
> on the track quite a bit the last 30,000 or so miles.
> 
> Don Mallinson
> 
> bjshov8@comcast.net wrote:
> 
> >There has been speculation that the ATX does not allow the engine 
> to "lug", and therefore reduces wear on the bearings.  With an MTX 
> you can run the engine under load at real low rpm's which is what 
> is theoretically bad for the bearings.
> >
> >
> >  
> >
> >> Just changed the connecting rod bearings at 190K miles on my 
> wife's 1993 ATX.
> >>I think it was a waste of time! The bearings had very little 
> wear. I just
> >>could not believe how clean the engine is! Only had a small oval 
> patch of
> >>copper showing, maybe 1.5 or 2 inches long. Not even all the way 
> across the
> >>bearing shell. We have had this car since 78K miles and have 
> only used Mobil 1
> >>synthetic oil, changed at 5K intervals. The new rod bearings 
> checked with
> >>plastiguage were right in the middle of the factory clearance range.
> >> Maybe the ATX SHO's can go without changing the rod bearings? 
> Even up to and
> >>over 200K miles?
> >>    
> >>
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