[Shotimes] rod bearings

Wed, 13 Aug 2003 19:17:22 -0400

Thank you Don.

A few months back there was a discussion on here in which several people
defined "lugging" as running below 2000 rpm.  I was a bit confused by this
since I was taught in the military that lugging was a condition best likened
to an airplane stall.  An engine is considered to be lugging when the RPMs
continue to drop even though the throttle opening was increased.  That is
the reason I responded the way I did.  IIRC there was no mention made of
throttle opening in that former discussion but the number 2000 RPM was
tossed about considerably.
Personally I drive my SHO below 2000 RPM all the time.  I cruise in 5th at
45 MPH on the way to work on a nice flat stretch.  I also run the engine to
7000 RPM almost every time I leave a stop.  I don't think that my driving
style contributed to early bearing failure.  After all 200,000 miles is
really not too bad for ANY motor.

Jim
'93 MTX
and 238,000 before replacing the transmission

-----Original Message-----
From: shotimes-admin@autox.team.net
[mailto:shotimes-admin@autox.team.net]On Behalf Of Donald Mallinson
Sent: Wednesday, August 13, 2003 6:49 PM
To: shotimes@autox.team.net
Subject: Re: [Shotimes] rod bearings

Jim,

I don't think anybody (especially me) said that running a
motor (including the SHO) at or below 2000 rpm is "lugging".

The definition, for this purpose of "lugging" is running the
motor at extremely low rpm (generally, for any motor,
between idle and about 1200 to 1500 rpm) and LARGE throttle
openings!

Big difference between just cruising at 1500 rpm and trying
to accelerate at full throttle at 1500 or less rpm.

When the motor starts bucking and has that rough rumble at
low rpm's and big throttle openings, you are going to do
damage that would not be there if you were at a higher and
more normal rpm setting.

NO manufacturer I know will advise running a motor like
this.  And it applies only to Manual trans motors.  Yes, you
can get SOME throttle application with an ATX if working
right, but not much, and that is the big difference.

Don Mallinson

Jim and Debbie Leyden wrote:
> I concur, lugging a car engine doesn't do anything to damage the bearings.
> One of the points that I have disagreed on that is popular on the list is
> that you shouldn't run it under 2000 RPM.  Heck, 2000 RPM in 5th is barely
> 55 MPH.  I can't believe that they would design a car that was "lugging"
at
> what the maximum posted speed limit was in those days.
>
> Jim
> '93 MTX
> replaced rings and bearings at 200K
>
>
>
> -----Original Message-----
> From: shotimes-admin@autox.team.net
> [mailto:shotimes-admin@autox.team.net]On Behalf Of John Weidenbenner
> Sent: Wednesday, August 13, 2003 10:34 AM
> To: 'David Schultz'; shotimes@autox.team.net
> Subject: Re: [Shotimes] rod bearings
>
>
> The 3.2 oil pump capacity is 25% greater than the 3.0 pump. This has to be
a
> major reason why the 3.0 is so hard on rod bearings. Not everyone believes
> that lugging the engine kills the rod bearings. Lugging the engine on a
worn
> engine will sometimes make the oil pressure light flicker at near stall
> speed, but that's just showing you the condition of the lubrication
system.
> I believe its just an old wives tail. Anyone have any real proof?
>
> Sometimes just rod bearing replacement will increase the oil pressure
> enough. To do it right replace the rod & main bearings and the oil pump.
>
> John W.
>
>
>
> Subject: RE: [Shotimes] rod bearings
>
>
>
>>Yeah, the rod bearings on my '95 were trashed at 86K miles. See Rod
>
> Bearing
>
>>Job:
>>
>> http://www.picturetrail.com/gallery/view?username=rsporter
>>
>>But, this was an MTX.
>>
>>One of our suspicions is that MTXs can have more wear if the engine was
>>lugged around, with poor maintenance playing a lesser role.
>>
>>Now, you are doing a 3.2, which I assume has spent it's life in front of a
>>ATX. What did the rest of the engine look like? Was the oil ever changed
>
> in
>
>>90K+ miles??
>>
>>Ron Porter
>>
>>-----Original Message-----
>>From: shotimes-admin@autox.team.net [mailto:shotimes-admin@autox.team.net]
>>On Behalf Of David Schultz
>>Sent: Tuesday, August 12, 2003 1:18 PM
>>To: shotimes@autox.team.net
>>Subject: RE: [Shotimes] rod bearings
>>
>>
>>This is true.  I am in the process of rebuilding a 3.2l, and have replaced
>>the main and rod bearings.  Where as the rods had considerable, but even
>>wear, the main bearings had considerably less visible signs of wear and
>>probably didn't need replacing.  The rod berings however, did not have
>
> much
>
>>life left in them.  This on an engine '94 engine with 90,xxx miles on it.
>>
>>Dave
>>
>>
>>>I see it as the other way around. Rod bearings, by design, take more
>>>punishment and are more susceptible to failure. Mains have a rather easy
>>>life (relatively speaking). I see the loss of oil pressure due to wear on
>>>rod bearings.
>>>
>>>Ron Porter
>>
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