400 cracked block?

[Schurkey]

Nothing wrong with a PROPERLY MACHINED "reman crank".

Given a choice, I'd rather supply a usable core to my favorite automotive machinist, and let him grind it for me. I have a basic distrust of "production-line" reground cranks.

At least verify that they've left a decent filet radius on the journals, and it spins smooth 'n' easy in the block before you put the rods on it.

I gotta say, I'm concerned about the rod you're saying is out-of-round. I think you need to take care of that before you bolt it around a crank journal.

 

[TBMG270]

Nothing wrong with a PROPERLY MACHINED "reman crank".

Given a choice, I'd rather supply a usable core to my favorite automotive machinist, and let him grind it for me. I have a basic distrust of "production-line" reground cranks.

At least verify that they've left a decent filet radius on the journals, and it spins smooth 'n' easy in the block before you put the rods on it.

I gotta say, I'm concerned about the rod you're saying is out-of-round. I think you need to take care of that before you bolt it around a crank journal.

Thank you for the input. This site is loaded with knowledge. My apologies if all this seems kind of basic or stupid questions. I'm no stranger to turning wrenches but this is the first time I'm completely re-doing a bottom end myself. While I understand it all for the most part I second guess myself and need others opinions before I feel comfortable with it. So from what I've read, tolerance for out of round is half a thou. Should I be looking into buying a set of rods? Or replacing just the one? Like I said I have other rods that are the same as the ones I'm using. The powdered metal type the vortecs have, but the pistons that are on them are visibly different, the skirt is much shorter. I don't have a scale but I'd imagine the weight would be off.

 

[Schurkey]

Pop out the one goofy rod and piston, have a machinist resize it. No need to buy a set, or even one unless you wanted to.

My next 5.7L is going to get flat-top OEM pistons from an LT1/TBI Caprice, and powdered-metal rods. The pistons are about $100 for .030-over, a little more for standard or other oversizes. And I have the rods already.

 

[Hipster]

No builder thats any good would line hone or take block any bigger than spec. King and acl are .001 smaller than a clevlite and all of them offer a "x" bearing thats a extra ..001 clearance. Scat always has the better bearing finish but counter weights are usually out of time and harder to balance. Eagle easier to balance. Callies compstar is best out of the 4340 ones

Not speaking specifically making the hole bigger but cutting too much off the main caps and moving the centerline of the crank closer to the cam when line boring.

 

[TBMG270]

Pop out the one goofy rod and piston, have a machinist resize it. No need to buy a set, or even one unless you wanted to.

My next 5.7L is going to get flat-top OEM pistons from an LT1/TBI Caprice, and powdered-metal rods. The pistons are about $100 for .030-over, a little more for standard or other oversizes. And I have the rods already.

Well I just ordered a bore gauge online, should be here in a couple days. I'd rather have the right tools to check everything and make sure it's just that one that's out of round. And when a rod is resized, how is that done? Is the hole just made bigger? Or is the cap cut down a thousandth or 2 and then it's opened back up to original size?

 

[Schurkey]

The older rods, with a smooth parting line at the cap/rod junction, got the caps cut down a couple thousandths, and then the hole was honed to size again. This has a minor effect on the center-to-center length of the rod--but they weren't made all that accurately to begin with. Nobody really paid attention.

The newer rods that have the "cracked cap technology" (as if that were something special, instead of just a cost-cutting measure) just get the holes honed oversize, then you have to play with rod bearings that have an oversize OD to match the rod, and an undersize ID to match the crank.

 

[TBMG270]

The older rods, with a smooth parting line at the cap/rod junction, got the caps cut down a couple thousandths, and then the hole was honed to size again. This has a minor effect on the center-to-center length of the rod--but they weren't made all that accurately to begin with. Nobody really paid attention.

The newer rods that have the "cracked cap technology" (as if that were something special, instead of just a cost-cutting measure) just get the holes honed oversize, then you have to play with rod bearings that have an oversize OD to match the rod, and an undersize ID to match the crank.

Oh ok that makes sense. Mine are smooth, matter of fact I'm not sure if I've ever seen the cracked type on a sbc. Not that I can remember anyways

 

[TBMG270]

Pop out the one goofy rod and piston, have a machinist resize it. No need to buy a set, or even one unless you wanted to.

My next 5.7L is going to get flat-top OEM pistons from an LT1/TBI Caprice, and powdered-metal rods. The pistons are about $100 for .030-over, a little more for standard or other oversizes. And I have the rods already.

Question for ya, so I bought a bore gauge and micrometer to measure everything the right way. The mic is a starrett and the bore gauge is a used but in great shape Mitutoyo and neither one was cheap. These are not new to me, Im comfortable using them. Had my buddy who's a machinist double check and he got the same results I did. So from what I gather anything more than .0005 out of round is NFG. Couldn't find any factory specs so just going by what I've been told on here. I measured vertically and at about a 45 degree angle bothbdirections from that. Cyl. #1 .0014 out of round #2-.0005 #3-.0006 #4-.0005 #5-.0011 #6-.0018 #7-.0011 #8-.0013 and #8 is the one that was knocking. Could less than .002 really be all that bad? I made sure the gauge wasn't sitting in one of the recesses for the tang on the bearing or on the line where the rod and cap meet. Someone please tell me I'll be alright to just throw this thing together already lol

 

[Schurkey]

Your total oil clearance is around .002.

Now you're going to have up to .0018 of out-of-round on the bearing housing (rod bore).

Nothing good will come of that.

The questions you should be asking are "Do I replace the rod bolts when I have the rods resized?", and "Since it's mostly coming apart anyway, should I pop the pistons off, and have the assembly balanced, too?"