So how bad is it to have a 0.009" taper in your cylinder?

[Frederick Smith]

Bentley sez.........08mm (.0031") is the acceptable wear limit.

The first measurement is taken 10mm below the top of the bore,
the second in the middle (top to bottom)
the third 10mm from the bottom.

The measurements can't be taken while the engine is in an
engine stand due to bore distortion caused by the weight
of the block being cantilevered off one end.

Perhaps the measurements weren't taken properly? Although
a good shop would know the proper method, it can't hurt to
ask. If the first measurement were taken at the very top
of the bore, where the bore is virgin (no piston ring travel),
the difference top to bottom would be very different.Tyson Varosyan wrote:
> The engine is an MC that came out of an '87 5000T. I tore the block apart
> because the #1 cylinder had low compression. I found that the head gasket
> around the #1 cylinder had failed and that no other damage was apparent.
> Given that the block was torn out of the car, I decided that it may be a
> good idea to take it to a shop and get new rings and main bearings changed
> out. The guy at the machine shop measured the cylinders and said that they
> will need to bore the them, which means new pistons, etc, etc... However, he
> said that the taper in the cylinders was only 0.009" between the radius at
> the top of the cylinder and the bottom and that the rest of the engine
> looked to be in very good shape. The walls are smooth, no groves, the oil
> looked nice, etc. The taper he said was too great to just do a simple ring
> job, but was not too catastrophic to absolutely require a rebuild.
> 
> I am now a bit torn. With the motor already out of the car and torn apart,
> it is tempting to throw some $2500 at it and get new pistons, get it bored
> out, balanced, get the crank and rods nitrated, etc and pretty much build a
> race motor. On the other hand, I could just have them "deck" the head, throw
> a new head gasket on there and call it good.
> 
> What do you guys think? Is 9 thousandth of an inch worth a rebuild or should
> I just snap it back together and call it good?
> 
> Tyson Varosyan
> Technical Manager, Uptime Technical Solutions LLC.
> tyson at up-times.com
> www.up-times.com
> 206-715-TECH (8324)
> 
> UpTime/OnTime/AnyTime
> 
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