i'm buying a new engine to build that has a spun bearing. i plan on doing a complete rebuild with new bottom end and all anyway to build it tougher. will the spun bearing ad any significant costs or trouble since im already replacing the bottom end?
thanx,
chris

 

Yes.

If it's a rod you'll have to turn the crank journal down (probably replace the whole crank if it's really chewed up) and and remachine the big end of that rod pretty good, maybe just replace it is often easier. Chances are you'll be remachining all of the rod's big ends anyway just as a normal part of the rebuild so it's not as big a deal.

A spun MAIN bearing is a different story. When they spin they chew up the block main saddles. Align bore and hone job is not usually part of a typical street performance rebuild and so would definitely be more money. Plus you still need to machine the crank or probably replace it completely.

If there's any way you can start from a tired-but-undamaged bottom end you'll be WAY ahead of the game money-wise, trust me. I don't recall actually PAYING for a small block with a spun bearing ever. Pick up a good junkyard core for $250- it'll usually cost you less in the long run than fixing one with serious bottom end damage.

 

And, if a block had a blow-up in it, it's full of metal shavings; and needs to be COMPLETELY torn down, including the cam bearings and ALL the oil passage plugs out of it; and rifle brushes run through every oil passage to get rid of the chips.

Don't pay very much for it, unless it has LOT AND LOTS of good parts in it that you can re-use. Otherwise, like Damon said, if it's just some stock stuff, it's cheaper to just go to the junkyard and buy more, than it is to fix a motor that's smoked like that.

 

well, its a 3.8L tubro out of a GNX thats goin in the Camaro. not as easy to find or as cheap as a small block.

 

Isn't the block just the same as every other Buick 3.8?

 

you gotta get the crank turned.

 

buy it, scrap the shortblock and keep the turbo setup and whatnot. Just get another 3.8L out of some granny driven olds delta 88, buick park ave, etc etc, from the late 80's, and build that up. Put in new forged internals and whatnot.

 

Then you have even more of a reason for not trying to half-a** it.

So yes, the fact that the motor is blown up WILL add significantly to the costs of using it. No doubt about it.

 

An align-bore job on the block can run you another $150 to the cost of machine work you already need to do, like a bore on the cylinders ($100), plus a hone ($80), plus cleaning the block, and changing the freeze plugs and cam bearings (another $100). But if you're doing a serious performance build, you'll be doing this stuff anyway, so you should probably get the block checked for cracks too. If you're going with all new internals, you won't need to worry about the condition of the pistons, rods, or crank for that matter. BUT, if it did spin a main bearing, it can cost you depending on how bad the saddle is, as mentioned above.

 

it will cost a little more than 100 to bore all the cylinders to, its usually around 30 per cylinder. thats what the machine shop here told me.

 

$8 a cylender here

sometimes living in hick town helps

 

I don't think we're talking about some hick-town out-in-the-woods tractor veterniarian job here. This isn't the kind of motor whose machine shop work goes to the low bidder.

Or, wouldn't be, if it was mine, at least.

I'd be looking for somebody that has the right knowledge, experience, and equipment (high $$$/hr shop rates) and is willing to take the time to do it right (high number of hrs) so that I wouldn't be watching some sweeper truck sweeping the shrapnel my new motor created and spread all over the race track as I was paying the fine for an oil-down and putting my car back on the trailer. Not the cheeeeepest guy that would shove a tool through the block.

But, that's just me. I'm kind of weird that way I suppose. A motor like that would get a torque plate bore & hone, measured deck height, align hone (or bore if necessary), balancing, etc. etc. etc. I doubt that $30 a hole would get it done right, let alone $8, in amongst all that other stuff.

Catch me some time when I'm not in such a good mood, and I'll tell you what I REALLY think about crappy cheeeep low-bid machine work.