Measuring cylinder size

[stevend34]

Hi All, I'm putting new rings in my smokey Sierra GB13 and trying to figure out if this motor bored out at all. The pistons have “1.00” stamped on them (nothing else). Is this an indication they are stock size?
I've used a vernier calibre, but depending if I put pressure on it or not the measurement changes.. and yes, that only measuring the top of the bore...
Anyone have a dial bore gauge I could borrow? Any other tips when looking for evidence of stock size vs oversize?

(re smoke: yes, have already done valve stem seals and performed wet / dry compression test ).

[greyghost]

if you measure the bore correctly, you meed an internal micrometer or a bore gauge.
however, you will find that it's oval from about halfway down to the bottom of the stroke.
this occurs as the crack pushes the pistons sideways, it all has to do wit stroke to rod-length ratio.

rings along won't stop the smoking, you need to put new liners in. and this for a suzuki engine, just isn't worth it yet.

[stevend34]

Thanks for that. Not exactly what I wanted to hear! Oh well I’ll try rings and see what happens….

I also found a “N 100” on the rings. Does anyone know if this indicate standard size or oversize?

[greyghost]

typically rings aren't marked with their respective sizes. there is always a first.

clean the tops of the pistons, if the block is over sized it will be marked in the tops of the pistons, as will STD size bores
if possible post up a pic of just one piston, and I'll try and decipher the size for you.

I would also be keeping an eye out for a good replacement engine too, they are relatively plentiful and usually not too dear.

[stevend34]

Thanks. Will keep a look out for a motor.

Here is pick of piston and ring with N 100:

[stevend34]

while talking tech. What do you make of different color valve on number 1?

[gwagensteve]

I would have thought 1.00 was 1.0mm over stock. That should be easy to measure with a vernier on the top of the block. As Mitch points out, g13’s are open deck and ovalise their bores. If the bores are already +1 then I don’t think you can rebore.

Unfortunately G13’s don’t respond to a hone- they’ll start smoking again pretty quickly. They really need to be rebooted with a torque plate on the block. As Mitch points out, the machining work cannot be justified based on the price of the motor.

I think the piston markings for oversize pistons are in the FSM but I don’t have it handy now.

[greyghost]

just check the bottom flange of the block to make sure this number wasn't an assembly number.

there will be 4 numbers in a row (like 2 2 3 2), these were used on the assembly line to get the right pistons into the correct hole, as there are not all the same size.

but looking at that piston pic, it looks like 1mm over which is close to .040 thou over bore.

number one cylinder looks to be running about right, the rest are burning oil.
number one valve is white cause its hot, with minimal cooling unlike the intake valves that have fresh charge flowing over them.

[stevend34]

Just reporting back on the results from this one. They ended up being stock size. ordered new rings, honed the bore and installed them.
Have probably done something like 500Km since installation and no smoke! So far so good!