The Big Rod Discussion!

[zin]

A simplistic way to diagnosis a rod failure is as follows: a separated rod will generally be related to RPM and/or rod bolt failure. If it separated at the small end, then the stresses where too much for the design of the rod and/or a flaw or stress riser in/on the rod, be that too heavy a piston, too much RPM or both, it will literally be pulled in two. This mode of failure also has the unpleasant effect of creating what I refer to as "a rotary hacksaw", that tends to try and saw the block in half! The other mode is when the big end comes apart, this is generally due to rod bolt failure, not the rod itself. A bent rod is most commonly due to more compressive force than the rod was designed for, be it cylinder pressure, water in the cylinder, or other debris (valve heads, etc). I don't know how deep people want to get into rods and their part in an engine, so I won't get into rod length, etc.
Hope this is helpful to at least one of us!

Mike

[8valves]

Did the rod bend due to over-revving and the piston crashing the chamber?

No damage to the head in that particular case, but the piston was visibly shorter at TDC than the rest!! Took it out and it had a nice obvious whoop to it halfway through.

Like I mentioned, this is an aluminum rodded motor that I saw this on. That could make a difference I suppose.

[Sloride]

So, to quantify our rod selection and help me make an informed rod choice. we have...


A) Stock Refurbished (400ish hp 700 grams)

B) Eagle H-beam ("up to 650hp")

C) K1 H-beam ("Anything I can throw at them")

D) Carrillo H-beam (The ZEUS of our rod world)

X) GRP Aluminum (+/- 453grams!!! not a street rod )

Could someone fill in the approximate rod weights + recommended power/stress levels (rpm please )

info on other rod choices is also welcome

[GLHNSLHT2]

So if you have a 2.2 and you want to make maybe 600hp and run 8k rpms or more what rod would be the one to use?

[turbovanman²]

So, to quantify our rod selection and help me make an informed rod choice. we have...


A) Stock Refurbished (400ish hp 700 grams)

B) Eagle H-beam ("up to 650hp")

C) K1 H-beam ("Anything I can throw at them")

D) Carrillo H-beam (The ZEUS of our rod world)

X) GRP Aluminum (+/- 453grams!!! not a street rod )

Could someone fill in the approximate rod weights + recommended power/stress levels (rpm please )

info on other rod choices is also welcome

Ok my list-

My TII rods that I removed the parting line and had them balanced-692 grams
Stock TII rods, untouched-710 grams
Eagle EDZ SRT rods-573 grams
TU Billet K1 rod-600 grams

Stock std Mahle 2.5 8 valve piston-366 grams
Sealed Power .020 2.5 cast piston-362 grams
Wisco .040 forged 2.5 slug-368 grams
My 2.5 JE's with rings and a small hole-404 grams
TIII std Mahle piston-418 grams

Stock Dodge pin-125 grams
Wiseco wrist pin-122 grams

Std rod bearings-43 grams

So if you have a 2.2 and you want to make maybe 600hp and run 8k rpms or more what rod would be the one to use?

I would say K1 or Carrillo's at $1400,

[Mario]

Per Chris W:

TU Billet Rods- 600grams

[GLHSKEN]

2.2L Wiseco Pistons 432-434 grams. (I've bought 4 sets.

[sdac guy]

So does anyone have any first hand experience with the Mechart rods? I have a set of them in a spare 8V motor that was built many years ago... Not sure if I should pull them at some point and press them back into service on another motor or not I've heard they were crack prone but again, only what I heard, never seen any break.

I bought a set of the MP Mechart rods about 10 years ago at the Mopar Nats. I heard some stories about them after I got them. At SDAC-8, Jerry Mallicoat was one of the folks on the tech discussion panel. Since he was around Shelby when these were introduced I asked him about them. He said that while he might use them in an N/A application, he would never use them in a turbo motor. While very strong, they are just too brittle. He said when they break, and they do, they take a lot of the block with it. His words were something like "one of these broken spinning around can cut a block in half."

The recommendations on them I have now heard over the years is, have them magnafluxed before using them to be sure they are sound before they are installed. Don't use them in a forced induction app, and more recently, if used in competition in a N/A app, change them out every year.

I have a friend who races SCCA with a N/A 12.5:1 cr motor, which he spins to 8500 rpm on a regular basis. He uses the Mecharts. He has two more sets and wants to buy my set as spares because he is going to start changing them out yearly just to be safe.

A prettier rod was never made though!

Barry

[2.216VTurbo]

Thanks Barry, never heard that they were brittle and not well suited for boost. They were on a ~250 whp motor for like 10K miles, I was either lucky or living on borrowed time

[Mario]

Glad I didn't buy them when I had the chance! Thanks Barry.

[sdac guy]

Thanks Barry, never heard that they were brittle and not well suited for boost. They were on a ~250 whp motor for like 10K miles, I was either lucky or living on borrowed time.

When I quoted Jerry, I didn't really mean to imply that dozens of those rods haven't been used successfully by many folks, including use in turbo motors.

So I don't know if the "borrowed time" is accurate. But what cooked it for me was that Jerry did say, "If it was me, I certainly wouldn't use them in my turbo motor."

Barry

[turbovanman²]

2.2L Wiseco Pistons 432-434 grams. (I've bought 4 sets.

Weird, wonder if the 2.2's are a heavier construction?

Did you take out the wrist pin?

[csxtra]

Weird, wonder if the 2.2's are a heavier construction?

Could it be because 2.2 pistons aren't tuna cans like the 2.5s are?

[MiniMopar]

Yep, longer skirts on the stockers.

[TurboJerry]

Exactly!! Sounds like an echo of the words I just wrote above Jerry

I can think of one instance where horsepower will definitely bend a rod and that's if a cylinder is hydro locked.

Chris-TU

I should make it a habit to read others posts before I post! DOH!!!!

[GLHNSLHT2]

Quote:
Originally Posted by GLHNSLHT2 View Post
So if you have a 2.2 and you want to make maybe 600hp and run 8k rpms or more what rod would be the one to use?


I would say K1 or Carrillo's at $1400,

Would the K1's live? Simon is the only one with an opinion on this?

[Mario]

Would the K1's live? Simon is the only one with an opinion on this?

GRP Aluminum rods. If you're going to be making that power from an 8V 2.2, and spinning that high, you'll obviously be running this at the track, or just making 5th gear pulls on the highway.

You really should start a thread and tell us the recipe for 600HP and a powerband that goes to 8,000 RPMs from a 2.2 8V. I'd really be interested.

[turbovanman²]

If race car only then yeah, Aluminium, if not, then either K1's or Carrillo's.

[Frank]

If race car only then yeah, Aluminium, if not, then either K1's or Carrillo's.

Whats that based on? Where is the facts behind it?

While I dont like Eagles, even they can handle most anything we can throw at it. I would prefer K1 and know they could handle alot of power as seen on Supra and 4G63 cars.... of course that is just what I read nothing more.

[turbovanman²]

Whats that based on? Where is the facts behind it?

While I dont like Eagles, even they can handle most anything we can throw at it. I would prefer K1 and know they could handle alot of power as seen on Supra and 4G63 cars.... of course that is just what I read nothing more.

ACK, time and time again were told NOT to use aluminium rods in a street car, you of all people should know that.