Powder forged rods, good read on strength strong

[Guest]

The rod in the pdf link in the top left of the page looks exactly like my 3900 rod sitting on the floor next to me, every ridge, notch and machined surface.

It appears that the stock forged powder metal rods are very strong and if I read correctly stronger than the previous steel forgings. I think I'll scratch the swap to forged steel idea and use the stock rods with forged pistons in my planned forged 3900 build.

http://metaldyne.com/metaldyne/sections/powdermetal/media/ConnectingRods.pdf

Great article here, I know there are two sides to every story but this one's the rebuttle to an attack on the PM industry by the old competitor;

http://www.metal-powder.net/business/jun2005.asp

[Superdave]

I just wish we knew at what RPM would they fail at.. lol

[Joseph Upson]

If they are perported to be stronger than stock forged steel and the old 5.7s were good to 7k (and that was probably valve train limited) maybe 8k is a fair asking. The concern however is with how much the additional length weakens it relative to the shorter 5.7 rod possibly detracting from its additional material strength. 6500 rpm is good enough for me.

[ForcedFirebird]

How similar are the 3500 and 3900 rods? That pic looks exremely similar to 3500 rods. Based on the fact that they are in fact cracked, I would think they are of the same material.

Now, has anybody confirmed the 3500-up cranks? Seems like powder forging would be a viable option for cranks, and explain all the forged characteristics the cranks have, along with the added weight.

[Joseph Upson]

How similar are the 3500 and 3900 rods? That pic looks exremely similar to 3500 rods. Based on the fact that they are in fact cracked, I would think they are of the same material.

Now, has anybody confirmed the 3500-up cranks? Seems like powder forging would be a viable option for cranks, and explain all the forged characteristics the cranks have, along with the added weight.

My 3900 rod looks exactly and I do mean exactly like the rod in that picture, from the notch top left of the big end to the two dimples on the cap and the machined outline with the step like figure where the cap joins the rod.

The cranks are not powder metal, I saw GM cut a 3.6L crank on How It's made. They didn't say it but I recognized the engine.

[ForcedFirebird]

I'm going to look again, and maybe capture a pic, but it looks the same as a 3500 from memory.

[Joseph Upson]

I'm going to look again, and maybe capture a pic, but it looks the same as a 3500 from memory.

It is likely the only difference between the two rods is one is floating and the other pressed pin.

[Joseph Upson]

Another good read on PM rod strength + LS1 facts

Excerpt:

"Rod length is 6.1 in., .400-in more than the LT1/4 rod. The extra rod length reduces rod angularity and piston speed which decreases friction and noise and increases durability. LS1 rods have no balance pads making for less overall mass and allowing the engine to rev quicker. Undoubtedly you're asking, "Hey, wadaya mean 'no balance pads.'? How do they balance the rods, then?"

Well, they don't.

Small-Block rods were held to a weight tolerance of ±5 grams, per end, after balancing. The LS1's PM rods are manufactured to a tolerance of ±3 grams for the small end and ±4g for the big end without machining for balance. Such are the advantages of a net shape.


Bottom line: The LS1 rod is the strongest connecting rod ever used in a GM, production, mid-displacement V8"

Whole story: http://www.idavette.net/hib/ls1c.html

[Superdave]

hmm, alot of local guys have said that the LS1 rods were pretty crappy.

[Joseph Upson]

hmm, alot of local guys have said that the LS1 rods were pretty crappy.

Need more detail than that, for instance compared to what. It's probably easy for some LS1 owners to make that claim but considering the rods are in production engines making an awful lot more power than the the production traditional SBC of yester year in stock form they must be stronger in some way.

I wonder if they are arriving at that conclusion at stock power levels or after they've pushed the engine well past the 300 hp mark it already starts out at with nitrous and blowers. If I recall correctly the only 300 + horsepower production GM V8 between 1980 and the mid 90s was the ZR1 Corvette and that wasn't a small block chevy car and the LS1 is capable of more power than it produced with just two valves per cylinder.

I think this is a matter of lack of appreciation for what they really have. I read a Hot Rod mag article yesterday on an LS1 boost up to 700 hp by a small performance company that put their trust in the crappy LS1 rods with custom pistons for the particular combo they offer for sale. Perhaps there was an upgrade at some point.

[Superdave]

I can't find the thread anymore but iirc they were saying that the rods were failing above 6K RPM..

[Joseph Upson]

I can't find the thread anymore but iirc they were saying that the rods were failing above 6K RPM..

hmmm, 60 degree rods aren't.

[3400-95-Modified]

hmmm, 60 degree rods aren't.

I'll second that one... I'm tapping 6700 rpm on my 1-2 shift, and last night it was hitting the limiter, which was 6900, so I had to back the 1-2 shift down 100 rpm.

[sprucegagt]

hmmm, 60 degree rods aren't.

Apples and oranges. Even if the total HP output of both engines were the same, loading per rod is completely different.

[3400-95-Modified]

They have more rods per HP tho... LOL

Or would it be less hp per rod... lmao