The bore will move a good bit after the plates are taken off. If the bores a dead straight, there is a good chance plates were not used. Aftermarket blocks are more stable than stock blocks.
I think .0004-.0005 is acceptable. Those numbers will hurt your feelings if you write them on paper, because engine builders like things to be "perfect", but I don't feel as if you would see any performance loss.

make sure the piston measurement is taken at the correct guage point on thr piston with a micrometer. This guage poit varies greatly from piston manufacturers. See you piston spec sheet foe where to measure. Than transfer that measurement to a dial bore gauge. Actually the gauges from Summit and Jegs work well. They are not as good as a Sunnen, but who has $1200 laying around to buy a tool that will only be used a few times.
If you are truely concerned, torque the heads on the bare block, flip it over on the stand and measure the bores with your gauge from the bottom.

All good info!! Thank you all for you comments.

Please keep them coming!

How far are you from Dart, it's their block maybe have them bore and hone it to fit the new pistons.

Hey Dick - give Joe Soller a call at Champion Performance 586.755.7400 a shout. He does the majority of the machine work for the area performance shops as well as their own builds. He'll be able to get you setup or can do the work for ya. Tell him Neil sent ya.

Dick,

I try to get bores within a couple of "tenths" .0002" from top to bottom. It takes a lot of time to do this properly. I always let the block cool off for an hour or so before a final measurment and hone, they will move around a little as they cool off.

Although I have tried as hard as I can, I have yet to see a Dart block move more than a tenth or so when you put a torque plate on it ?? GM blocks certainly move, but I have yet to see it on a Dart block. I still use the plates, but really wonder sometimes if you need them on the Dart's

Also, as some others have mentioned ...... you CANNOT measure roundness with a bore gauge. Only size between 2 points on the cylinder. Only a CMM or laser type measuring device can tell you if the cylinder is actually "round"


Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Thanks Bill, that is the info I am looking for. Trying to learn something as go. Tell me what a DMM is. I would like to see info on that process.
Hearing a lot of ideas on how people look at this subject. Very interesting! Motor building has always had a lot of questions in my mind.

Dick

I would also plate hone it with the same head gaskets you intend on running also

Dick - I think you mean CMM. It's a coordinate measuring machine. It's a very precise robotic measuring device. I use to program one for an aerospace company, and prototype stamping company. We did the Cobra R parts, and the gen 1 dodge Viper prototype work.

It costs about $165 per hour to use one, plus programming time. Not really feasible for engine measurements.

Thanks WJB.. I kind of figured it was a high dollar experience.

Thanks!
Dick