five7kid

iTrader: (14)

According to the service parts list for the ZZ 350 engines, the ZZZ, ZZ1, ZZ2, and early ZZ3 engines had the forged "pink" rods, while later ZZ3 and ZZ4 engines received the PM rods. I just picked up a core short block that was called a "ZZ4", but it may have actually been an earlier ZZ version. At any rate, it does have the forged pink rods and forged steel crank, so whatever its origin, it should be the "good" crate motor stuff.

Are there any advantages to either type of rod? All of my projects to date have involved standard production SBC hardware, so this is a little new to me. The answer probably won't make a whole lot of difference, since my plans are to put it together with hyper pressed pin pistons, FM trimetal bearings, and ARP rod bolts, but for future reference it would be nice to know the capabilities of what I have on hand.

FWIW, the block casting # is 14093638, crank 14088532, and block s/n is VH243811 (no VIN). I'll have to look again for date markings. I can't read the rod #'s.

ME Leigh

Pink rods are the same as regular stock forged SBC rods, but a little stronger. They may also be alittle heavier.

PM rods are far superior to the forging process rods. Better strength, lower weight, and much better consitency between rods and within the rod itself.

five7kid

iTrader: (14)

All I've been able to determine about Pinks so far is:

- Forged
- Used first in the LT-1
- Hand picked, matched sets
- Finished to higher standards

They certainly don't look like the regular production SBC rods I'm used to.

I understand the production advantages of PM's, but hadn't heard that they were necessarily stronger. For that matter, haven't actually put my hands on any.

VetNutJim

The pink's are handpicked for weight matching and treated to exactly ONE stage of shot peening.
They DO have some pink paint on them.
They "USED" to be the hot ticket that we HAD to have.


The PM ones are the newer technology from the General.

ME Leigh

PM's are stonger because they have a better grain structure, metallurgy, and uniformity!

Anyway it doesn't really matter the bolts are the weak link and have always been so.

Air_Adam

PM rods aren't rebuildable though, from what I've heard (I think that has something to do with resizing for new bolts?) So if you have a core, the pink rods would already be a good thing to have, no?

five7kid

iTrader: (14)

PM rods are sintered as one piece. The "cap" is then fractured off (in a precise fashion) and the fractured halves locate each other when bolted back together - unlike the ground halves of "normal" rods. However, that also makes them un-resizeable.

Forgings have long been known for strength due to grain flow in the forging process. Having uniform grain structure is not necessarily a strength enhancer - although it can be a consistency enhancer.

I'd like to see some side-by-side tensile tests of full-up rods pulled by pin & journal. Agreed, though, the typical weak point is the bolts.

ME Leigh

The new PM rods are definitely rebuildable, only the first couple of years were not.

bnoon

Correct. I was corrected on this issue too when I first went looking into new rods a year or so ago. Now I have '97 LT1 rods that didn't have to be resized (but it's nice to know they could have been if needed, especially since I got them on "the Bay"). They are now sitting in wait for the block work to be completed.

From what the machine shop tells me, as well as what an ex Ford powertrain engineer tells me, is that the rods can be rebuilt only a limited amount of times as the heat trating process on the crank end machined sufaces (both bearing and cap to rod faces) are very thin. Once that heat treated "skin" is machined through, failure can happen rather rapidly. Rebuild once = safe, more than once becomes questionable.

five7kid

iTrader: (14)

That doesn't make any sense. Surface heat treating is for wear purposes, like drums, rotors, and in some cases, crank journals. Rods should be heat treated throughout (if in fact they are) for strength.

What may be happening with PM rods is you need to grind off all of the fractured surfaces from the rod & cap in order to do the resizing. You'll have to take off a lot more than you would "regular" rods, so the caps would get thin from the material you would have to remove in order to get past the fractured surface.

That I would believe. The guy who sold me the shortblock said he resizes PM rods, perhaps he hasn't come across some of the earlier ones.

If the later PM rods are resizeable, I'd guess they stopped fracturing them and started cutting them. Just a guess, as I have no direct information.

ME Leigh

Don't quote me on this, but i remember hearing that you use oversize bearings that fit the larger hole of the rebuilt rod.

JP84Z430HP

Just FYI....
The PM rods I bought for my engine about 5 years ago are NOT fractured, but machined cap to rod mating surfaces.

As for the heat treating, Case hardening (surface treating) would not be needed for a rod, even in the bores. In the big end bore, the bearing is the wear surface (Actually the film of oil is, but that's a different story) and the small end the pin is press-fit into.

HTH
JP

Parrydise7

iTrader: (1)

Have you checked out "Bowtie" connecting rods? This is from the GM Performance Parts Catalog:

14011090 Bow Tie Connecting Rod (5.70" long)
Heavy-duty Bow Tie connecting rods are engineered to withstand the stress and strain of racing. These premium quality rods are forged from tough 4340 steel which has been vacuum degassed to eliminate impurities. Dedicated forging dies are used for the two different center-to-center lengths to minimize rod weight. Fatigue tests have shown that Bow Tie rods can endure more than 10 million cycles at racing loads without failure! Unlike the bolts and nuts used in production connecting rods, heavy-duty Bow Tie rods are equipped with aircraft quality 7/16" bolts which thread directly into the rod fork. Alignment sleeves positively locate the cap on the rod. Bow Tie rods are machined for pressed wrist pins, and are shotpeened to enhance their durability.

five7kid

iTrader: (14)

I'm not looking to buy new rods. I was mostly curious why they switched from pinks to PMs partway through the ZZ3 engine run, and if I should be concerned about that since mine are pinks.

bnoon

It is my understanding that the machined surfaces need a surface treating in order to retain integrity of the powder metal forging's machined surfaces, even not being a wear surface. If not done, the compressed powder internal surfaces could fail very easily because of the lack of "togetherness". Think of it as styrofoam with all of the little pellets of metal being stuck together... put a layer of clear tape over the top of the styrofoam as skin and the taped piece of styrofoam would hold together better than the non-taped one. Cutting the tape skin creates a failure point when stressed... just as machining through the heat treated skin would on the rods.

The rest of the rod wouldn't benefit from surface hardening because of the skin that is created within the sinter forging process. This also kills any ideas that cryo treating does any good for sinter forged internals.

JP84Z430HP

Hmm.... Sounds good! Doesn't sound like a for sure thing, and I would like to know! Maybe that's why they originally used the cracked cap design on the first one's, to save a surface that get's heat treated. Although, I would think that they would just heat treat the entire big end, and the entire small end. Realistically, I would think that the entire rod would get it all at once.....

Does anyone know if the rods used in the vortec trcuk engines are the same PM rod's used in the ZZ4? I have a couple sets here, and would like to know what they compare to, if anything!

F-BIRD'88

May be I'm "old school" or just getting old.
but there is something about "powdered metal"
reminds me of the old Powered Metal tail light trim bezels of the typical 50's and 60's car. Not very strong.

I'd go with the tried and tested Forged LT-1 Pink rod. Up to about 430-450hp they are hard to beat. For a extreme race SBC You're going to surely go aftermarket anyways.

I think if memory serves me well GM rates the PM rods at 400BHP.

just my

JP84Z430HP

Same rod they used in the ZZ430....430 HP 430 torque...

I ain't skeered to be usin 'em!

anesthes

iTrader: (12)

Interesting. I was always told the gm "X" rods were the strongest.

In any event, stock rods are not bushed, and don't come with ARP hardware. For the price of eagle or scat, I don't see the point. For what you pay to have the pistons pressed on and off the rods, you're halfway into a set of new ones.

-- Joe

five7kid

iTrader: (14)

This all may be true if you're getting new or different rods. These are what I have, so these are what I'm going with.

What I really wondering was if the factory went from the pink to PM in the performance crates because of performance/reliability, or cost. My bet would be cost.

(Oh, $25 to press the pins - does that mean new Eagles or Scats are $50 a set?)

Floor guy

Amen, My vote is on cost savings

anesthes

iTrader: (12)

$25 eh? They charge $50 off, and $50 on around here. Do they used a sunnen where you have it done or?

Eagles, scat are $159

http://cgi.ebay.com/ebaymotors/ws/eB...943948045&rd=1

So, you can see why using stock rods and stock hardware is just. Dumb.

-- Joe

anesthes

iTrader: (12)

Cost savings at the expencive of a ruined motor. Sorry, thats dumb.

Sure, many people, including myself over the years have cranked 450+hp outta stock rods + crank, but .. For what the "good" stuff goes for now, you'd have to have your head checked to do it these days.

-- Joe

Floor guy

You are probably right. A major manufacturer would probably never make a change to reduce cost. I have seen many engine failures in extremely hp engines fail. Rarely is a rod to blame. A pm rod went in a 355 hp crate motor. The crappiest of rods will hold up to that number below 6k. In the corperate world cost dictates every decision made. GM could probably care less what we do with a production rod in a strong motor. As long as it lives in theirs.

anesthes

iTrader: (12)

When I used to buy f-bodys (I used to sell parts on ebay back when these cars were popular), I'd get a TON in with "locked up motors". Usually the #2 rod broke at the wrist pin. Dunno..

I'd rather spend afew extra bucks on a rod, then have it ruin a good block.

The 4 bolt 1pc roller motors are getting harder to find for some reason.

My earlier point was basicly, if hes using "used" rods, hes gonna need to press pistons off and on at min, he SHOULD mic them, mag them, etc. And .. It just isn't worth it. WHen you can buy a set, with bushed small end, arp hardware, allready magged, x-rayed, and from a BETTER forging to begin with.


-- Joe

Floor guy

I never disagreed with your statement that good stuff is too cheap not to use. I personally would not use a stock pm rod. I simply agreed with a prior post regarding cost because gm's butt is so tight. I foolishly have been running stock rods w/arp bolts on spray into the 10's and never hurt one "yet". I have seen 1 pm rod fail. For some reason it snapped just above the big end when the motor was shut off. Never seen anything like it before or since. The owner foolishly changed 1 rod and went back to racing. Never knew why it failed but left a bad impression in my head.

My rods are the x rods. I would be too sceered to put a pm rod thru my paces

anesthes

iTrader: (12)

I ran "X" rods for jeez. years.. On my lst motor, about 5 on there alone, and years before that. Was always the "rod to have" because the good stuff was too expencive.

But for my new build, I went with a h-beam rod. ($300).. But I'd have at LEAST gone with the scat or eagle i-beam.. The x-beams are in a box collecting dust.

-- Joe

SSC

Well then better give those rods a nice fresh stripe of pink so next time we'll remember. I'd say yes they are quite fine I'd expect a pin to break free or the rod bolts to fail before the actual rod broke. Just have them magnafluxed to be on the safe side and forget about that being a weak link. Reminds me, anyone got an extra $1200? My machinest has a set of Carrillo rods he's been pushing me on. Oh yea I a warm fuzzy holding them.

five7kid

iTrader: (14)

Already been magnafluxed. ARP bolts going in. Tanking took the pink paint off.

Price for pressing the pins might have been sweatened because I bought the block from him.

Anybody know the correct shade of pink to use?

ME Leigh

How much did all the rod work cost? $100?

If you ever have to resize them, just get aftermarket ones!