To Resize Connecting Rods or Not?

[65 Cuda 340]

It's unfortunate, because a lot of shops don't even check length. They just get the hole round.

They don't check straightness either. Putting together a 340 once, with reconditioned rods (this was back before we had generally available aftermarket rods). All the valve reliefs lined up except for one. Took that one out, the rod was twisted enough that you could see the twist with your naked eye.

 

[tvt59]

Kind of off the subject. I've ran stock 340 and 360 rods in a lot of braket cars. New bolts and polished beams. Resized and lengths equalized. Bushed and non bushed. Back in the 80's and 90's aftermarket rods were available but VERY out of my budget. We ran those domed Speedpro pistons that felt like the weighed 2 pounds each. We ran those engines 1000's of passes shifting at 7800 rpm and crossing at a little over 8000 rpm. I never broke a rod. I've never seen one broke that didn't have a spun bearing or something else. I admit that we were only making about 500 hp back then. But the stock rods are pretty tough. I've seen a lot of SBC broken stock rods. But the SBM stock rods are pretty tough. But they are heaver than the SBC.

 

[74 Cuda]

Engine blocks have a register or dowl to locate the main cap. Everytime you remove and reinstall the cap it sits in the same location. Connecting rods without dowls use the bolt shank to locate the cap. If bolts are replaced the rods needs resized.

 

[66fs]

I just replace rod bolts and do not always resize. But I have a real dial bore gage and a setting ring gage for the bore I'm checking. I also worked in a metrology lab checking and setting up production gages. I check before and after rod bolt replacement. Like a lot of things in an engine, unless you take extreme care, how do you keep the same center to center distance when you are grinding the cap mating surfaces and then the hone? The factory stuff was pretty good from what I have seen, some rebuilders, not so much. I'll buy a virgin engine long before I'd buy a rebuilt engine. 60's and early 70's stuff is good, later stuff, seemed get cheaper and not as good.

 

[CRUZE 418]

My opinion but, everytime a rod gets resized, it gets weaker. I had an unknown set of 7/16" rods in a big block Chevy boat engine. Thrown together at the end of the season. Had it out 3 times. Tore it down for the winter and checked the rods, they were already out of round on the big end. Sold them to some street guy and bought a good set of used Crower rods, those rods never got out of round over the years till I sold the boat. No way of knowing how many times that set of rods had been resized, or maybe it was a bad metal recipe.

 

[Swinger 340]

Oh yeah. I've had a few engines over the years marked with the Maltese Cross. That means non standard size "somewhere".

In case someone don't know where to look for those stamps, they are at the top of the block below the head on the driver side front. Remember, they are for a stock block and may have been changed after a rebuild. As everyone says here, CHECK, tolerances before closing up a rebuild.