Are the rods in late model, truck vortec motors
different, or better, than the ones that were used in our thirdgen 5.0 and 5.7 motors? When did "powder metal rods" come out, and are they in any stock motors? Same question on "pink rods" Thanks for any info.

 

Fan,

The "pink" rods are supposed to be heavy duty factory rods, but the powdered metal are actually just as strong if not stronger. The PM rods are also generally better balanced as sets, better balanced end-to-end, and are inherently stress-relieved. They are by concensus able to handle duty in up to a 450 HP engine with no other special treatment.

PM rods first appeared in SBCs in 1993 IIRC, on the LT1 and L99 engines.

Stock rods in most ThirdGens were plain old cast iron, poorly finished, poorly balanced, and not as suitable for higher HP/RPM use as the PM rods.

 

The only failure of PM rods I've seen firsthand was on an LT1 running 12+ lbs of boost. He blew at least two head gaskets, had the block o-ringed, and one of the PM rods evidently became the next-weakest link.

Not a condition you'll see on a normally-aspirated engine, so if you can get a good price on PM rods I'd say go w/ them.

 

Correction: Small block rods were never cast. They always had forged rods.

 

O.K. So I got lazy and used the term loosely. From my understanding of the process, most "plain" SBC rods were cast into a billet from nodular iron, then forged into shape in a standard two-die drop forging process. So while they are techically "forged", they are not what I would consider an equal to a common aftermarket forged steel rod, or even the factory rods that were forged from a 4340 steel billet. They still started life as an iron casting, much like the nodular cranks. If my understanding is wrong, please feel free to correct me again. Someone has to keep an eye on me...

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Fan,

Incidentally, if you DO decide to use the PM rods, don't be surprised as I was when I first removed a set. While the caps look like they have broken off, they are designed that way and are just fine. (they were made "broken"). You can get a full set of PM rods for around $200.00. (Part # 12495071)

 

jeff don't you just hate it when you know exactily what you meant and no one else does?

 

Yeah, a person really has to watch his step around here. A lot of these people realy know their shiznit, and it's easy to get caught being lazy.

Technically, the PM rods are "forged", too, but not what we would commonly (and, lazily) call "forged" rods.

 

Thanks! everybody. Now I have a true or false I need answered on the subject. "All vortec motors use PM rods" T or F ?

 

I despise using terms like "All", "Always", "Never", etcetera, since as surely as politicians will lie, someone will usually find an exception. However, I'll stick my neck out (and get ready to swallow my foot) and say that to my knowledge, all '94 and later LT1, L99, and Vortec truck engines used the powedered metal con rods.

One wild card is the 262 V-6 engine (L35). While it is a "Vortec" engine, and shares the same bore and stroke dimensions with the 350, the parts used may not have been the same. They could be the same, since the earlier versions used standard 350 pisons, rods, bearing shells, etcetera, but they aren't necessarily the same.

There are a few differences in some years. For example, some early PM rods used cracked caps, and later PM rods had a machined separating line so the rods could be serviced. I think this change happened around '93 or '94, but don't quote me on that one. There seems to be some discussion about which engines got which, and whether cracked-cap rods were used in any '93+ LT1s at all. "Never", "Always", "All", or "None" - who knows for certain?

All I can say is that there is a very good chance that any Vortec engine you open will have PM rods with machined caps.

And since you raise the possibility of using PM rods in your build, remember that the lower mass of the PM rods and LT1 pistons will require some significant material removal from the counterweights on a "standard" 350 crank. The LT1 piston/rod assemblies are actually much closer to the mass of a 305 assembly than the older-style 350 factory assembly. If you have the resources to do a lot of crank machining, you can balance the crank to the piston assemblies if you want. However, in the interest of saving machining time and effort, if you are planning to use a stock cast crank, a 305 crank might be a better starting point, since far less machining will be necessary to achieve a neutral balance.

Then again, if you have access to a set of used-but-nice rods from a Vortec truck engine, that crank should already be closely matched, and require only the normal balancing. I think that you may be pleasantly surprised to find the piston/rod assemblies are already fairly well matched from the factory, due to the more consistent manufacturing processes. I was.

 

OK I think I'm there now. The balance thing was something I wasn't considering. What I have is two low mileage 98 vortec truck motors that were out of wrecked, or flooded trucks, and one 87 4bolt main motor that was just worn out.......... so I have two sets of PM rods in good shape, two roller setups, one standard vortec crank that can stay standard, one vortec crank that needs turned, one set of standard vortec pistons that are good, one standard vortec block that needs a sleeve in one cyl or all 8 bored, the worn out 87 stuff, and a really nice set of vortec heads all for $500. I think I can put together a nice 350 4 bolt with the vortec rotating parts, and heads, and can sell the rest seperate, or in a short block, and come out pretty cheap on the deal. Wish me luck, or throw anymore red flags you might see. Thanks to all.