I was looking at Chevy crate engines and one of the descriptions said the engine had "powdered metal connecting rods". I have not heard of this before. Is this something new?

Paul

They have been around for about 10 years. This is what GM has replaced the "pink" rods of yesteryear with. They are the rods sued all the way up to the ZZ430 (350cid/430hp/430lb-ft) small block. They're decent and will be OK unless you start making power over the 4-450hp range.

They have been around for a year or more and are supposed to be as strong or stronger than forged parts.
Guy

They started advertising them in the mid/late 90's if I remember correctly. Supposed to be a substitute for the LT-1 " Pink " rods. I have an engine with a set in them, but it needs built, and I personally have never used them before.

They are supposed to be the next evolution in strength.
Heres a little light reading.
http://www.superchevy.com/technical/engines_drivetrain/shortblock/1510sc_howards/index.html
http://www.pickpm.com/designcenter/Conrod.pdf
http://en.wikipedia.org/wiki/Powder_metallurgy

Imho, they are STRONG like said, BUT I really don't think they are as tough as a forged rod!!

Take one of each and put them in a heavy vise and whack away at them both w/ a 10 pound sledge and see which one breaks and which one bends and that will tell you if I am right?

And I think I am right in saying that most forged rods break their bolts before they break their beams.

pdq67

What hasn't been said is that the powdered-metal rods are MUCH LESS EXPENSIVE to make--once you've bought the specialized equipment.

There's very little machining needed; they come out of the forging machine nicely shaped.

So, YES, they can be a good choice for a medium-performance build; and YES, they can be an economical choice. They are NOT the be-all and end-all of connecting rod technology.

One downside to at least some powdered-metal rods is that they use "Cracked-Cap" or "Fracture-Cap" technology--put simply; the rod is forged in one piece with a deliberate weak-spot where they want the cap parting line. Then they whack the forging to bust off the cap. Works fine--just like it did in 1959 in chainsaw engines. The problem is that you can't resize the rod in the same way that you do with traditional rods. To re-size a cracked-cap rod, you have to bore the hole oversize and then use a bearing with an oversize OD in addition to the correct bearing journal ID.

Thanks Guys. I had heard of the fracture cap technology as I had seen it in a Chrysler engine from the early nineties but now I know why. I guess the only down side is not being able to resize the rods.

Paul

Powdered metallurgy parts are supposed to be much stronger than cast, probably not forged though. If I recall from my manufacturing class correctly, using PM technology makes the part much more resistant to crack development and dislocation movements. Another advantage is it is easier to add alloying elements and the grain development is not so "random" and poorly oriented as in cast. I know they make most gears out of it now, so its got to be pretty tough.

Powdered metal rod ain't worth 15 cents. I knew a guy bought a new set for racing engine for limited budget for a IMCA open wheel and it lasted one weekend.

Why not use eagle sir rods? They work well and are forged steel. If you can afford it go with eagle "h beam" rods,they hold up real well, just make sure the rods have the proper rod bolt for the intended application. Rod bolts are one of the most overlook areas

the PM rods have been around since at least the '92 model year when they started putting them in the LT1 in Vettes, and in the "ZZ" series crate motors, starting with the ZZ2 or thereabouts, and continuing up to the ZZ4 of today.eventually, they started using them in everything with a small block in it. i don't think GM sells a small block engine assembly (crate or replacement) with anything but PM rods any more.
every small block rod used from 1955 up until the switch to PM were forged- but some of them were given better hardware and got shot peened after the forging process and given a pink stripe painted on them to denote that they were the "good" rods.
as far as durability- i put probably close to 20,000 miles on a set in my Nova, and they never let loose on any of the many 7000+ rpm blasts i did with that car over the 4 years after that motor was put in it. and that was straight out of the box with the stock bolts.