Chevy powdered metal rods

[rfoll]

What year did this stuff show up? I like the piston design/ring package and the fact that they all weigh within a few grams of each other. I'm looking at a low mile motor an I would like to know what's in it. The previous design pistons were horrible.

PICT0401.JPG

[CGT]

What year did this stuff show up? I like the piston design/ring package and the fact that they all weigh within a few grams of each other. I'm looking at a low mile motor an I would like to know what's in it. The previous design pistons were horrible.PICT0401.JPG

Started early to mid 90's intermittently in 350 (K) and 350 (P) engines. By 96 they were pretty much in all of them.

[cardo0]

Rumor was the PM rods showed up with the GEN II LT1 but the motor out of my '94 Z28 had regular forged rods - I have the pix on another PC if you need them. I can get the weights to if you want them. The pistons are definitely hypers though. Sil-vo-lite has them dirt cheap with coated skirts. Part numbers: 1476HC, 1479H, 3476HC.

Now if you do a search for rebuilding the GEN II LT1, you should find an Engine Rebuilders article mentioning the LT1 350 crank is balanced lighter more like a GEN I 305 rather than a GEN I 350 due to lighter hyper pistons and PM rods.

Hope this what you were asking about.

[Schurkey]

The service-replacement for the Caprice/Fleetwood/ "B" and "C" body TBI engine '91--'93 had powdered-metal rods, and flat-top pistons. The Pickups may (or may not) have had powdered rods, but the pistons had a slight dish. About 1/4 point different compression ratio. The Caprice/Fleetwood pistons use a 2.0/1.5/4mm ring pack. About the only downside is they're .010 short on compression height.
https://www.summitracing.com/parts/slp-h597dcp

I don't know about Firebird or 'Vette.

I wouldn't trust that ALL engines got the powdered-metal rods the same year.

[rfoll]

The service-replacement for the Caprice/Fleetwood/ "B" and "C" body TBI engine '91--'93 had powdered-metal rods, and flat-top pistons. The Pickups may (or may not) have had powdered rods, but the pistons had a slight dish. About 1/4 point different compression ratio. The Caprice/Fleetwood pistons use a 2.0/1.5/4mm ring pack. About the only downside is they're .010 short on compression height.
https://www.summitracing.com/parts/slp-h597dcp

I don't know about Firebird or 'Vette.

I wouldn't trust that ALL engines got the powdered-metal rods the same year.

The 1.54 compression distance makes them not such a bargain when you have to deck the block to get your quench back.

[pdq67]

Take an old standard forged SBC rod and a newer PM rod and put them in a great big Blacksmith, "Post Vice", and hit them both with a 10 pound sledge hammer and see which one bends and which one breaks is all I am going to say.

pdq67

[rfoll]

My street engines never have to deal with a 10 lb. sledge hammer. Having a nearly perfect balance factory engine is more important than the likelihood that it will ever see north of 5500 rpm. Most of the 100,000 mile Vortec engines I have found don't need to be bored and it makes for a really nice inexpensive short block.

[Schurkey]

About the only downside is they're .010 short on compression height.
https://www.summitracing.com/parts/slp-h597dcp

The 1.54 compression distance makes them not such a bargain when you have to deck the block to get your quench back.

1.550.

[cardo0]

The service-replacement for the Caprice/Fleetwood/ "B" and "C" body TBI engine '91--'93 had powdered-metal rods, and flat-top pistons. The Pickups may (or may not) have had powdered rods, but the pistons had a slight dish. About 1/4 point different compression ratio. The Caprice/Fleetwood pistons use a 2.0/1.5/4mm ring pack. About the only downside is they're .010 short on compression height.
https://www.summitracing.com/parts/slp-h597dcp

I don't know about Firebird or 'Vette.

I wouldn't trust that ALL engines got the powdered-metal rods the same year.

The 1.54 compression distance makes them not such a bargain when you have to deck the block to get your quench back.

I understand but I plan to deck the block anyways. I'm thinking of GEN II blocks using a thicker composite gasket. But If your going the thin 0.015" shim gasket route you want a higher compressed height. Then again the Sil-vo-lite 3437HC has a 1.56 c/h and coated skirts in 4.020" 4.030", 4.040", 4.060" sizes. 105 bucks at Jeg's! Can you beat that?

[peejay]

Take an old standard forged SBC rod and a newer PM rod and put them in a great big Blacksmith, "Post Vice", and hit them both with a 10 pound sledge hammer and see which one bends and which one breaks is all I am going to say.

pdq67

I have a PM rod from a Chevy engine that hydro locked. It is bent into an S shape, and twisted as well. The engine still ran, but it had a hefty knock from the piston slamming into the crankshaft.

[peejay]

Take an old standard forged SBC rod and a newer PM rod and put them in a great big Blacksmith, "Post Vice", and hit them both with a 10 pound sledge hammer and see which one bends and which one breaks is all I am going to say.

pdq67

Right on. PM is for cheap and quick manufacture, there is no place for any of it in a performance engine.

There are people (well, at least one person) in the 7s with a completely stock 5.3 bottom end, PM rods and all, running over 2 bar of boost and over 8000rpm.

What is your definition of "performance engine" if that is not good enough?

[midnightbluS10]

Rumor was the PM rods showed up with the GEN II LT1 but the motor out of my '94 Z28 had regular forged rods - I have the pix on another PC if you need them. I can get the weights to if you want them. The pistons are definitely hypers though. Sil-vo-lite has them dirt cheap with coated skirts. Part numbers: 1476HC, 1479H, 3476HC.

Now if you do a search for rebuilding the GEN II LT1, you should find an Engine Rebuilders article mentioning the LT1 350 crank is balanced lighter more like a GEN I 305 rather than a GEN I 350 due to lighter hyper pistons and PM rods.

Hope this what you were asking about.

Pm rods showed up in lt1 corvettes in 94 and f body's in 95, afaik and according to the gm lt1/lt4 book. So your Z, likely built in '93 for the' 94 model year, wouldn't have had PM rods anyway.

Reinforced by this article from Engine Builder Mag


http://www.enginebuildermag.com/2000/04 ... t1-engine/

[Warp Speed]

PM technology has came a long way since the mid 90s. It can, and is used for a number of parts in a performance/race engine.

[Krooser]

We built my son's B mod engine with PM rods out of a marine engine. Bought 19 take out rods for $80.00.... came from non winterized engines.

My machinist hates them but admits he's never seen one break on its own.

Howard's PM rods are their top seller and they claim they are the strongest they sell.

[cardo0]

Maybe a little off topic but years ago when I was a GTO owner and Pontiac fan the Pontiac 389 and 400 motors had what most thought an "ideal" rod/stroke ratio of 1.8.  Don't know how that claim came from but for some reason the Pontiac 389/400 motors where designed with long rods.  Cadillacs where even longer though I can't recall those lengths and would have to look them up.  Some more trivia is those long rods where cast iron.  Yes cast iron - not forged.  And what the major cause for rod failure in the Pontiac was the weak stock rod bolt - not the rod.  Again I don't know the how they got that information on rods but Peterson and Johnny Angles wrote about it.  Well forged Pontiac rods where pretty expensive in those days so the common practice was to recondition the cast rod but install better bolts.  All that left me with the impression its not worth the experience in street motor to spend for fancy forged rods.