LS1 LQ9 Stock Connecting Rods

**LSP1** · 03-11-2008, 10:45 PM

I am new to the site and I did a quick search on the factory stock "cracked" connecting rods but didn't seem to come up with what I was looking for. Maybe I was doing the search incorrectly... I was looking for what people are doing with the stock "cracked" connecting rods after installing ARP rod bolts. I heard a customer saying that most people he talked to are sending them to a machine shop to get the ARP rod bolts put in and then "re-conditioned".

This doesn't make sense to me since you can't technically recondition a cracked rod, all you can really do is check the connecting rod bore to see if its within spec (2.224" - 2.225" in or 56.505-56.525 mm). I like to run the connecting rod bore more to the lower side of the spec for a performance engine and after installing ARP rod bolts in the past the rod generally gets tighter on the bore size like below the 2.224" figure or gets slightly out of round. With a conventional Chevy connecting rod you can grind the rod / cap and then honing the rod bore brings it back into my ideal range BUT with these LQ9 / LS1 cracked rods the bore didn't change, it stayed right at the high side of the spec and pretty much round. If it were just one rod I would say maybe it was just a factory defect or maybe something happened to that rod over the course of its 78,000 mile lifetime but it was all 8 rods that were at their high side limit and none changed after torquing them with the ARP bolts.

At this point there is no "re-conditioning" the cracked rod because the rod and cap can't be cut. By honing the rod bore it will only make the rod bore larger (past 2.225") and therefore causing the bearing crush to be less desirable. So my question would be how is everyone who installs ARP rod bolts in their stock cracked rods getting them "re-conditioned" at their local machine shops?

**C&Cbird** · 03-11-2008, 10:49 PM

I don't see why you couldn't grind the rod/cap and hone it out on a cracked rod.

**LSP1** · 03-11-2008, 11:14 PM

These rods are what is called a powder forged connecting rod and if you ever saw a piece of cast iron that was broken in half its all jagged and rough, its not broken straight across. When these rods are manufactured they are all one piece and then scored at the parting line of the rod / cap and cracked to separate the two. Some cracks go straight across, some go at a steep angle and some have a step in the crack. When you separate the rod and put it back together it fits perfectly but you can't grind either surface because the material you would need to remove to get both surfaces flat would be more than is possible to remove without ruining the rod. I wish I could find a picture on the net to post but I can't. I will take a few tomorrow and post them here because its easier to see what I'm talking about than to explain it.

**C&Cbird** · 03-11-2008, 11:26 PM

I know what they look like, I rebuilt my LS1 and have help several others. I don't ever remember seeing that steep of a crack, most of the ones I've seen were really small. I put ARP bolts in mine, but I don't remember them being off any, I'd have to ask my dad though, he'd be more likely to remember. I know next time I do a motor for my car, it'll have aftermarket rods.

**mrr23** · 03-15-2008, 10:17 AM

the old traditional SBC rods were machined flat across the caps. so, when someone had them 'reconditioned', both cap ends were resurfaced and the bore resized, to ensure roundness.

LS1 style rods cannot have this done to them.

**99transamC/FIA** · 05-17-2008, 09:55 AM

I would not run them rods if the bore is that big. That is now you spin rod bearings.Save your money and buy a set of Scat's i-beams. There are less then $300.
Just my 2cents