[south65ss]

Just a bet wth a friend. All Chevy v8 rods I have seen are forged. All Chevy 230 and 250 six cylnder rods I have seen are cast. Do I need glasses??

[DoubleVision]

All small block chevy rods are forged. In the 1990's they started using a new rod which is powdered metal also known as "PM" rods that are stronger than the older "X" and "O" rods.

[ap72]

Originally Posted by DoubleVision

powdered metal also known as "PM" rods that are stronger than the older "X" and "O" rods.

wanna bet?

PM rods were done ONLY because they are cheaper, several OEM's that switched to them are switching back to forgings because they are stronger and more importantly don't flex as much as PM rods. PM rods will rarely break but they will distort pretty easily- which isn't so great for rod bearings.

That being said, as long as you give a little extra clearance on the rod bearings PM rods can work well in most street applications. I actually have a set I'm using a build right now, because I had them on hand.

[DoubleVision]

You know, when I grow up AP, I wanna be just like you. Always right.
Lt1 Pm Rods Or Gm Pink Rods

[ap72]

Well thanks I guess. I'm not always right I just keep my mouth shut unless its something I know something about.

[cool rockin daddy]

PM rods like all sintered metals will snap before they distort. DV, you are correct. Maybe some actual stats on the subject:
http://findarticles.com/p/articles/m.../ai_101939306/

[DoubleVision]

The article was indeed a good read, thanks CRD. I learned something from it and I like to at least learn something everyday.
What I always liked about PM rods is there smooth appearance. No weight on the cap, and no forging line down the middle of the casting gives the PM rods a nice clean look. Don't get me wrong. I used the "X" and the "O" rods plenty of times and had good service out of them. But when the PM rods came out and I read the article written by a GM engineer on how they were stronger than the classic rods and could take more punishment before failure when I did my next build I used PM rods and they're all I've used ever since.

[ap72]

This has been beaten to death on speedtalk, and those guys are a lot more knowledgable than anyone on this site. I'm not a metalurgical engineer but I do know that-

The pro's won't use them
The top manufacturers won't make them
Some of the top oems stopped using them and switched back to forgings
I also know that rod bearing failures are one of the biggest failures on vortec engines

I was told by people much more knowledgable than me that these rods flex which can lead to spun bearings, its best to run clearances on the high side- as a result when I have to use pm rods I set the clearances on the high side and use bimetal bearings.

I will admit that they look cleaner, but looks don't mean much.

[cool rockin daddy]

Do whatever you want, AP. I mean, my god, you're all of 25 and you've built thousands of engines and of course you know more than the GM, Ford, and Chrysler metallurgy and con rod engineers put together. I mean, they're using them in DIESELS. Chrysler's 392 hemi has, ta-daa, pm con rods. But your comment about pm rods distorting more than a conventional rod says everything we need to know about your "expertise".

But gosh, I really do appreciate you slumming around here and gracing us with your presence yet again when you could be hanging around the geniuses at speedtalk. I really thought we had cured you of your attitude a few years back but it looks like it didn't stick.

[sbchevfreak]

Finally, someone else has seen what I saw long ago.....

Originally Posted by ap72

I also know that rod bearing failures are one of the biggest failures on vortec engines

SOOOO not reality....

Just so you know, AP, unlike you, I do this for a living, and have worked on literally thousands of these engines. The main failures are intake gaskets, usually leading to overheat, killing the head castings, or popping a head gasket. Also, another failure area is the distributor drive gear, but usually only after a couple hundred thousand miles, so not really a "major" failure. In the years since 1996 when the SBC vortec started seeing widespread use, the number of vortecs I have seen with a rod knock is maybe 5. The number with intake/head/gasket failure? I lost count.

As for the rods bending, that would preclude using fracture fit caps, as the "sinter" the rod as one piece, then break the cap off the big end. If they were easily susceptible to bending, this process would not be feasible.

[cool rockin daddy]

Well this is what you get when you have a guy who reads a lot of books on his way to collecting meaningless degree after degree posts things. We've asked him before to list all the engines he's built but we get silence.

BTW, good catch on the rod bearing failure misinformation on the Vortec he posted.

Was wondering, is it the formed "sealer" already on the gasket that is the problem with the gasket causing the failures?

[cobalt327]

Originally Posted by sbchevfreak

Also, another failure area is the distributor drive gear, but usually only after a couple hundred thousand miles, so not really a "major" failure.

My experience is much more limited than yours, but I too have seen worn distributor gears coming from Vortec engines. I thought it was a coincidence, but maybe it's actually more widespread than I had originally thought... and I know I'll be on the lookout for this in the future, so thanks for that.

AFA PM rods go, my opinion is they're every bit as good as previous rods, but like the previous rods they should get better hardware and also like the previous design, the PM rods should be replaced by aftermarket rods if the engine is going to be raced or revved considerably more than a stocker. In other words, use them if they meet the needs. Replace them if they don't.

[Silver Surfer]

Originally Posted by cool rockin daddy

Was wondering, is it the formed "sealer" already on the gasket that is the problem with the gasket causing the failures?

I believe I read it is a two-fold problem. The early Vortec heads used 6 intake manifold bolts on each side (new heads use 8). And I believe the plastic on the gasket cracked.

[Custom10]

Originally Posted by south65ss

Just a bet wth a friend. All Chevy v8 rods I have seen are forged. All Chevy 230 and 250 six cylnder rods I have seen are cast. Do I need glasses??

Can someone answer the poor guys question does he need glasses?

[cobalt327]

Originally Posted by Custom10

Can someone answer the poor guys question does he need glasses?

Yep, needs glasses.