I have a couple of sets of mopar LY piston rods and thinking about loading them up for scrap metal. Does anybody buy these to use anymore?

I've got two sets myself, don't think they will ever be inside an engine again!

R.

I thought LY rods were good rods?
Did I miss something? (Again)


Too heavy? Break at low RPM? What?
Not good to 6000 RPM?

They're good but old these days. I put a set in the 71 Road Runner, I figured with pistons maybe 2/3 the weight of stock that they'd last a long time with a beam polish and good bolts.
You just don't know where they've been for the last 45 years is all.

Sheldon

The 535 LY rods were in production from their debut in the '50s until the late '70s. For the longest time, they were the best rod for the RB engines because no one else made anything.

They have one major fault: 3/8" rod bolts. Yes, the same rod bolts found in 318s are in every LY rod. While they may be great at 6500 rpm in a 360, they are overmatched in a 440 at the same speed, slinging around a piston that weighs at least half a pound more, with longer stroke to boot. Plus they are heavier than some aftermarket rods, but that's not the killer. Plus, they are made of decent but certainly not high strength steel.

When you start out with a set of used LY rods, you don't know how many millions of cycles they have gone through, how their ultimate tensile strength has decreased, but they can lose over 30% of their strength from fatigue. So you buy new rod bolts and pay someone to rebuild them and that totals out to $250 or more. For just a little more than that you can get a 4340 high-strength steel rod that probably weighs less, is stronger and has a 7/16" rod bolt. I know which way I'd go.

From the 'bay listings of sold parts, looks like I'd better get mine up for sale.

If you will hang 600 gram pistons on them with lightweight pins and keep the revs below 6000, no strokers, they will probably be just fine. But is it worth the risk?

R.

How many have toasted ly rods on a street or street/mild strip build?

I broke a couple before I learned to machine 100 grams out of the forged Six Pack slugs that everyone used way back when.

Sheldon

Back in 92 I swapped race cars with a fellow (now considered friend) on a Sunday evening. The following Saturday I started it up (only 3rd time sense Sunday) drove it into the shop to fix the brake lights a things for street use. Pulled it back out of the shop & let it idle a bit with open fender well headers. Began revving it few times to about 2500 on the tach then it just stopped dead on a dime. I remember saying "that's not good"

I found the nut in the oil pan that I believe cause this. It had half of it's threads intact & the other half yanked out, leading me to assume that the nut was at the end of the bolt when the cap finally decided it couldn't take it any more. The nut was by itself with no bolt in it. It's puzzling though how it got that far without a failure first. But looking at the pic it appears to me that the nut was stripped off to the cap bent/broke the other bolt of about mid way. Wish I would've saved the nut.

I couldn't here the knock ahead of time, but my brother who was ~ 200' away said he thought he did just before it stopped on a dime.

When I got out to look, I felt to look under the car first, & there was the right rear freeze plug on the ground. I remember saying "that's not good either" #8 rod had come off, pulled out of the piston & was all wadded up in where the cam used to be. The cam broke just behind #4 journal, 2 lobes then a break, 2 more lobes & a break. #5 cam journal was still in its block journal.

I got word later, it was thought that I was really high rev'n the motor, but I was not. I don't rev motors that are cold, new, or unknown yet.

FWIW: the next motor that went into this same car was also a "someone else built". But this one I went in a retorqued everything. Saw it had ARP bolt & forged pistons so I eventually stepped up to 300hp shot of nitrous & had no stock rod failures. But I did find where all the stock main caps (& bolts) had been doing the Watusi. I guess it was at its ragged edge.

Yeah that's a crack that runs the full length of the pin,...somethings gotta give somewhere. lol.