main bearing bore

[fordperson]

Hey, I dropped off my I6 block at my machine shop and supposedly the mains are out of round, any ideas what might cause that? The block has really low miles and wasnt abused...

Tom

[fordperson]

PS the machine guy recommended align honing it, do I need new main bearings after this?

Tom

[fordperson]

nvm i figured it out

[$upraman]

So what's the story?

[CraigFL]

I'm curious too.... My first thought is that if he is only going to hone them, they probably weren't much out in the first place. I would also want to be sure that the right caps and torque were used to determine this condition. And lastly, how perfect does this really need to be??

[TheSilentChamber]

How perfect.. well anything they measure in thousandths of an inch- you might want it to be damn near perfect.

[fordperson]

for some reason im not getting thread notifications.. The story, its a S52 bmw m3 I6 engine, 60k on it... The engine was in perfect condition, good cr pulled hard numbers on the dyno... Its gettnig fitted with some CP pistons, rods etc... I had my machine guy check the clearances etc, he found the mains to be 1-1.5 thousandths off... 1 thousandths is still within specs according to bmw tis... in any case Im having it honed and new bearings + polished crank
Oh and the caps were marked when I took em off, He's using arp main bolts if that matters(probably not)

Tom

[$upraman]

Originally Posted by fordperson

for some reason im not getting thread notifications.. The story, its a S52 bmw m3 I6 engine, 60k on it... The engine was in perfect condition, good cr pulled hard numbers on the dyno... Its gettnig fitted with some CP pistons, rods etc... I had my machine guy check the clearances etc, he found the mains to be 1-1.5 thousandths off... 1 thousandths is still within specs according to bmw tis... in any case Im having it honed and new bearings + polished crank
Oh and the caps were marked when I took em off, He's using arp main bolts if that matters(probably not)

Tom

Well that's gonna cost a pretty penny.

How much exactly, BTW?

[fordperson]

1.4something(dont have it on hand) thousandths, supposedly there are many blocks that come like this from the factory... is 1.4 thousandths alot?
Im curious as to why this happend, to align hone the block its an extra $200 + 100 for bearings

Tom

[$upraman]

LOL.

Actually I meant how much exactly it's gonna cost you?

[fordperson]

well.. cp pistons, arrow x beam rods, ferrera oversized valves, bearings, guides, vanos were about 3.5gs+2g for labor... :>

labor=oversized valves installed(new seats/valves cut), port and polish(already done), cams/crank polished, align hone, tq plate borred/honed, blasted, baked, degreesed, painted block...

Tom

[$upraman]

I hope that bimmer is worth it.

[fordperson]

well worth it