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

[Tyson Varosyan]

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)

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