6.2 cylinder boring vs. honing with org pistons

[neo]

Hi all, I searched like crazy prior to posting and forgive me if this is redundant, but did not find the answer to my particular quesiton. I did however real rheems of great stuff from all the contributors and moderators regarding wall thickness, 6.2 -> 6.5 boring etc. Great stuff!! My question is: As I begin my rebuild of (what I believe) is a 660 block (83 van), I am looking to blueprint and ballance. I got a quote from what is very highly recomended "diesel specialty" shop near Raliegh NC, about 2 hours away. They have a very good reputation,a nd it sounds like I am going to send up the block and components this week for all the machine work and short block assembly. BUT, some folks have said I need to replace the pistons and overbore (.020 or whatever I can get away with) when doing this. Now if this was gas, I would certainly do that, but others have said the walls are kinda thin (I blelieve some of the data here cited .25 on average) and don't recomend going over. I wish to build a strong, long lasting engine, not a powerhouse. I am very nervous about the lower end coming apart, and wish to take reasonable precautions. More than willing to do a new set of pistons at .020 over, if necessary, but would rather stick with the standard bore if at all possible. One local shop says the bores will not be lined up properly and will not be parallel to each other or perpendicular to the crank centerline. What is the general consensus on this? Do most folks always slap in new pistons? The engine is an 83 with around 120k miles. So far it has looked really good as I tore it down. Any input is greatly appreciated.
Neo.

[simon]

It all depends on the amount of wear in the bores. 120k is not a lot of miles , so what happened that the engine is apart? Are there ridges in the bore, if not you could probably get by with new rings.
have that machineshop measure the bores and pistons and the crank for that matter, compare that to the specs and go from there.
it's a good idea to resize the rods as well.

If that local shop can't bore the block strait and true, DO NOT GO THERE.

[neepsjeeps]

Exactly what he said, any "good" machine shop can tell you what is required and discuss the options with you, hard to say what is needed with out seeing each cylinder and measuring each as well.
They as should be able to tell you how much boring it can handle, i dont know that block as well as others but i would be suprised if 20-30 over was a problem..

[More Power]

.030" is the max overbore recommended by GM for these engines, but you can buy .040 pistons.... Have the block checked for cracks, with particular attention paid to the center three main webs.

Jim

[neo]

Excellent info guys. Thanks a bunch. The engine is apart cause I pulled it from the old van that had set back in the woods for 10 yrs since it was last titled/tagged. Did not bother to try and start it cause the rodents had a field day in the intake and packed it full of crap. THat coupled with the long time and unknow condition, along with the fact it is going into a wagonner (fingers tightly crossed) which is a complete engine/drivetrain conversion, I just wanted to do it right from the get go. There is no ridge at all in any of the holes. They all looked very clean and good. Have not measured yet. The machine shop up the road (Raliegh) is much higher recomended cause Diesel is about all they do. I like the idea of going step at a time. First crack check, then cyclinder check then get busy with the clean-up.
Simon:what specifically do you mean by resize the rods? Is this big end or little, or both? Can I safely remove all the flashing from the parting line on the rods? How about the crank? THere are several large-ish pieces of flashing I would like to carefully grind off. Thanks again!