cruise98

Adrial:

What tolerance group are your pistons? It is stamped on the crown and on the block at each cylinder. Be sure you keep them in order.

All dimensions are in millimeters

For group 0

Bore 100.00 +/- .005
Piston 99.98 +/- .005

For group 1

Bore 100.01 +/- .005
Piston 99.99 +/- .007

For group 2

Bore 100.02 +/- .005
Piston 100.00 +/- .007

The wear limit is +0.080 mm for all sizes.

Granite 944

The .00787 is the out of roundness tolerance yes. I was refering to the max. wear limit of the cyl. bores, which is the .080mm. Sorry about the confusion. The .007" I gave was not meant to mean it was out of round that far (though they are out of round some, but at this point it really didn't matter much),it was a measurement of the smallest part of the bores as compared to max spec. for bores. And as you already know, everything in the FSM is in mm. Your measurement of .0008" difference in the bore probably means your ok for out of roundness. Now you need to know where your at for max. bore size, min. piston diameter, and if it exceeds a difference of approx. .0044" (at least on mine). Thats the max. clearance callout plus the wear limit on piston/cyl. clearance. You might still have a machine shop double check your measurements unless you feel real comfortable with your measuring processes. I don't have enough of the tools to even try, so I pretty much left it up to my shop to make the determination of it being in or out of spec. Another big reason I recommend people go to a shop that is pretty familiar with these engines. A lot of shops are not familiar with the machining of the alumsil blocks. Sorry again about any confusion.

adrial

I was thinking about this more...

Doesn't the crank girdle need to be torqued down again to measure the bearing holes? So couldn't the measurement of the bores be done at that time? Or does the crank actually need to be installed for the bore measurements? Getting ready to call up the machine shops and I want to know what I'm talking about. Also I would rather pull the crank and send it off to Lindsey ASAP...so if its not needed for the measurements and doesn't actually save a torquing on the studs, I would rather get the crank sent out of here. Also this will make the block much easier to carry around!

I see a bunch of line's that could look like one's stamped on the block by each cylinder...I guess thats the group markings?

thanks,
Adrial

Geo

The crank does not need to be installed when measuring the cylinder bores. Just have the crank girdle torqued to spec. Even better if you can find someone with a torque plate for the 944.

adrial

Thoughts on honing the bores, if done correctly?

Geo

The bores are not honed in the 944. It's my understanding that as long as you don't bore the cylinders, the finish should be just fine. If you bore the cylinders, you must lap the bores to expose the silica which is harder than the aluminum and prevents the galling.

This is a combination of what was explained to me and what I've read in the FSM. If someone knows otherwise, I'd be interested in hearing about it. But my understanding is unless you bore, you won't need to lap the cylinders.

cruise98

Adrial:

I responed to your PM, but George already gave you the correct answers.

Use some maroon very fine or grey ultra fine scotch brite pads to remove the carbon and glaze in the bores. Do not go crazy here, just wipe the bores clean. These engines cannot be "honed" like an iron block, but have to be polished with a special paste and felt pads. When simply re-ringing, polishing is nice but not required. Stick with the stock Goetze rings to ensure proper seating and ring seal.

After you get everything clean, scrub the bores with some ATF and lint free clothes to remove any embedded dirt/metal in the cylinder walls. Do this until the clothes do not show any dirt. Since you did not rebore/polish, this should not take long.