Heavy or light crankshaft for 4.5 build ?

[GoatBoy4570]

I did a search here and the internet "Connecting rod material" and found nothing about jeep rods, kind of a bummer that a Jeep Strokers form has nothing on this topic considering rods are a critical part of any stroker build ?

[jsawduste]

I did a search here and the internet "Connecting rod material" and found nothing about jeep rods, kind of a bummer that a Jeep Strokers form has nothing on this topic considering rods are a critical part of any stroker build ?

If you dig a bit deeper you`ll find several "Jeep" rods.

Scat makes a replacement

Russ has a rod of his design that he sells. Crankshafts also.

Eagle made an H beam rod that is actually longer than the factory 4.0 rod. My personal stroker has these.

Newcomer also has their propriety rod.

Each of these are a little different and unique to the specs dictated by the designer.

[Cheromaniac]

I did a search here and the internet "Connecting rod material" and found nothing about jeep rods, kind of a bummer that a Jeep Strokers form has nothing on this topic considering rods are a critical part of any stroker build ?

Ι believe that the stock 4.0 & 4.2 rods are cast steel.

[jsawduste]

[/quote]Ι believe that the stock 4.0 & 4.2 rods are cast steel.
[/quote]

That they are Dino, along with the block, crank, head and many other components found in everyday life. I`d bet the block might be a different mix than say the connecting rods.

Like Baskin Robbins 31 flavors of ice cream. By adding or subtracting various ingredients (alloys) the properties of the cast can vary widely.

This link shows just a SMALL slice of cast and the numbers. There are plenty of "mixes" and we are not even getting into after cast functions like heat treating yet, Just the base material here.

https://en.wikipedia.org/wiki/Steel_cas ... berg1334-4

[jsawduste]

[/quote]Ι believe that the stock 4.0 & 4.2 rods are cast steel.
[/quote]

That they are Dino, along with many other components found in everyday life.

Like Baskin Robbins 31 flavors of ice cream. By adding or subtracting various ingredients (alloys) the properties of the cast can vary widely.

This link shows just a SMALL slice of cast and the numbers. There are plenty of "mixes" and we are not even getting into after cast functions like heat treating yet, Just the base material here.

https://en.wikipedia.org/wiki/Steel_cas ... berg1334-4

[Pac8541]

First post anywhere on this forum and I’ve been reading all kinds of threads here.

I find this conversation absolutely fascinating. Makes me want to go back to school just to understand.

Thank you.

[GoatBoy4570]

I'm glad your enjoying the thread, your right metallurgy is a fascinating topic what amazes me is what they already knew decades ago, today steel is so ubiquitous its just taken for granted. I never did find out what jeep rods are made of and i suppose no one here knows, i'm just gonna assume they are 8620 same as what many cranks are made from.

[Tolemar]

All rods are forged and not cast. Cast cranks are not as strong as strong as a forged crank The 12wt crank is supposedly stronger than the 4wt cranks. If you look at most performance engines they all have counterweights opposite of every rod throw. I specifically wanted a 12wt crank for my build. Crawler not a racer.

[GoatBoy4570]

All rods are forged and not cast.

Jeep rods don't have a forging line so it's safe to say they are not forged, so the next question is "what are they cast from" my research has turned up next to nothing so from my perspective its pretty safe to say no one really knows, at least no one outside the factory where they were made.

That being said they must be cast from a half decent material as lots of people beat the piss out of them and i've never heard of a failure. I haven't heard of or read of those scrawny little bolts that hold the big end cap on failing ether, so over all Jeep rods, not much ta worry about here !

[IH 392]

All rods are forged and not cast.

The only AMC connecting rods that are forged are the 390 and 401, there is documentation from AMC that they offered forged rods for the 290 and 343 (and probably the 304 and 360, the scans I have are dated Feb 1, 1968) in the "Group 19 Parts Catalog", but I don't know anyone that has ever seen a set?
The cast rods are obviously some GOOD material, nodular iron?, probably cast steel of some sort?, the thin parting line confirms that they are indeed cast.

[Torqsplit]

This question about the specific rod material intrigued intrigued me, so i dug out the old Mopar Performance Jeep engines manual. For the 2.5 they say "Cast Nodular-Iron". 4.0 says "Cast Malleable Iron" and 4.2 simply says "Cast Iron". They give specifics for Length/ Wight and tolerances but no mention of the alloy #'s tho. I'd wager they're all nodular iron, but the 4.2/258 is an earlier design from AMC so who knows what casting materials they actually used. They certainly seem to hold up fine tho. The 4.0 rod is based on the 6.125 LA-small block design and has pretty well proven itself thru the years. Newcomer has certainly taken both setups way out there on his dyno runs!

[Cheromaniac]

They're probably cast nodular iron and that makes them rugged but also heavy. That's why they're used in low revving truck motors.

[IH 392]

The 4.0 rod is based on the 6.125 LA-small block design

The 4.0 rods are DIRECT descendants of the AMC 199, LATE ('71+) 232.

[Torqsplit]

OK I don't really have any info on the other AMC 6's, those just aren't well known to me.

[Tolemar]

I have built multiple engines and never seen a cast rod except maybe a Briggs and Stratton lol. Maybe I’m wrong but I really Don’t see how a thin cast rod can take the punishment. Heavy thick Cranks are a whole different story. Saying that I have built a supercharged small block Chevy with powder metal rods. https://findanyanswer.com/how-are-engin ... -rods-made
Anybody have a pic of these so called rod castings?