New Zealand Datsun Club

Hi all.

Just had to put new rings in my a12, some were cracked, the motor is already bored out to 60 thou too.

I have rubbed my finger in the bore & near the top they have like a ring taper only slightly though, is this anything to worry about or should I hone each cylinder??

Cheers guys

If you are fitting new rings you will need to deglaze (hone) the bores.

The cross hatch pattern that a hone leaves serves two purposes.
One is, the roughness acts like a micro file to wear the new rings to the same shape as the bore. this happens within the first 20miles, and then that roughness worn away.
the other job it does is, the thin hone lines hold oil, which helps lubricate the rings as they travel up and down the bores.
if the lip at the top of the bore can be felt with your fingernail, then you must remove it with a ridge reamer. (butler auto mart hire these out I believe)
if you home the bores yourself, it's very very important that you do it slowly. and as you hone it, move the hone up and down. this will give you the correct angle on your cross hatch pattern. I've seen tons of photos on the net of bores where the drill was going too fast, and the lines are too horizontal.
for what it costs, I'd just pay a shop to do it for you. then you know it's done right.

as Bart said if you can feel the ridge it needs removed, this may be what broke your rihgs

And it can easily damage the ring lands on the pistons too.
in a perfect work if there is a lip present in the bore, it's removed prior to removing the pistons from the block.

Rings don't brake unless something is wrong ie piston slap ring grove wear I would look further .

cheers guys, its on my racecar, might ring butlers in the morn, ta bartman for the explanation.

if 60thou over maybe look the the possiblility of sleeving the cylinders to keep the block still viable

an A12 block can stand a 120 thou overbore is the rule of thumb.

Bartman wrote:an A12 block can stand a 120 thou overbore is the rule of thumb.

whoops sorry ill re word what i meant if 60 thou over and want to keep it at that then look at sleeving