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Connecting rod discussion of aluminum vs Steel

15K views 25 replies 17 participants last post by  donlenzb 
#1 ·
I have been thinking this over for a long time. My engine consists of a DRCE 2 9.400 deck block with a 2.100 rod journal 3.750 stroke. It will see 9000-9500 rpms. It will be fed by the F3-139 making 2500hp or more. I'm trying to decide if a steel rod can live, or if aluminum rods are necessary. I have called Oliver, they pretty much told me they had not done anything like that before, and would be expensive to design a rod to live. I like the idea of the steel rod life, but if aluminum is the only rod that live, so be it.
 
#4 · (Edited)
499 c.i.d. - 4.600 bore x 3.750 stroke.

If your going to build and run a motor like that you better figure into the expense a rod maintenance program. Personally, I would run a MGP aluminum rod and replace them after 100 runs.
Your piston speed is not unmanageable but will requirer attention.

For comparisons......at 9500 @ 3.75" piston speed will be 5937 FPM, a Pro Stock engine runs around 6300 FPM and a 632 with a 4.75 stroke @ 8000 runs 6333 FPM
MGP and GRP are on my list.
 
#3 ·
If your going to build and run a motor like that you better figure into the expense a rod maintenance program. Personally, I would run a MGP aluminum rod and replace them after 100 runs.
Your piston speed is not unmanageable but will requirer attention.

For comparisons......at 9500 @ 3.75" piston speed will be 5937 FPM, a Pro Stock engine runs around 6300 FPM and a 632 with a 4.75 stroke @ 8000 runs 6333 FPM.

Blessings.........Ron.
 
#8 ·
If your going to build and run a motor like that you better figure into the expense a rod maintenance program. Personally, I would run a MGP aluminum rod and replace them after 100 runs.
Your piston speed is not unmanageable but will requirer attention.

For comparisons......at 9500 @ 3.75" piston speed will be 5937 FPM, a Pro Stock engine runs around 6300 FPM and a 632 with a 4.75 stroke @ 8000 runs 6333 FPM.

Blessings.........Ron.
and most pro stock motors have steel rods in them now too

we run steel olivers in our 525 f3 combo at 8500 rpm, no issues
 
#10 · (Edited)
" I have called Oliver, they pretty much told me they had not done anything like that before, and would be expensive to design a rod to live"


Interesting, Oliver told my builder last week they have a"extreme duty" steel rod for up to 2500hp that are being run in twin turbo cars with no failures... This is what he ordered me for my blower project.... EDIT maybe they just dont make it in your length
 
#12 · (Edited)
They don't make it in a 2.100 rod journal or that short from what the guy told me. Maybe they do, or the person I talked to thought I was a stroke. Happens once in a while, I have a speech inpediment called stuttering. Looks like aluminum rods will be the way to go, plus I can buy multiple sets for the price I was quoted on steel rods.
 
#11 ·
4.600x3.750 - man we've been threatening to do with with a roots combo for some time now.

I would think the biggest thing with a steel rod would be to keep a very close eye on the bearings. Being more rigid they're going to transfer more harmonics and more "bang" to the crankshaft. - I would think in that kind of app steel rods would likely have a noticable duty/life cycle as well as aluminum, thus though they might go 200 runs instead of 100. With the "crazy custom" cost difference, I personally don't see a benefit.
 
#13 ·
Outlaw Bill, Mark Wolfe does indeed run steel rods in his AA/T comp car. But the motor is something like 347"s which would have substantionally less reciprocating weight. Also the turbo's require considerably less gross power to produce the same power to the rear wheels. I think Mark is actually in the 2650+hp area.
You would certainly be on the fringes with a steel rod if you had one made for it. An aluminum rod would be a tried and true area and would serve you. Personally I prefer the MGP rods which use the A-1 rod bolts. If you order from them make sure you torque the bolt as they specify......one pull to full torque.

Have fun.........................Blessings.............Ron.
 
#15 ·
Outlaw Bill, Mark Wolfe does indeed run steel rods in his AA/T comp car. But the motor is something like 347"s which would have substantionally less reciprocating weight. Also the turbo's require considerably less gross power to produce the same power to the rear wheels. I think Mark is actually in the 2650+hp area.
You would certainly be on the fringes with a steel rod if you had one made for it. An aluminum rod would be a tried and true area and would serve you. Personally I prefer the MGP rods which use the A-1 rod bolts. If you order from them make sure you torque the bolt as they specify......one pull to full torque.

Have fun.........................Blessings.............Ron.
419 cubes
 
#16 ·
From Olivers site:

Big Block-Max Series:
This rod is engineered for
use in the most extreme
applications were power
adders are common, such
as big block turbocharged/
supercharged endurance
motors and blown alcohol
drag cars.


Last time I talked to them, the guy said RPM, stroke, weight (piston, pin & rod) and rod length were the factors. Said HP didn't matter.
 
#20 ·
I would think the combination of a blower putting stress on the crank and the rpm you are turning you would be much better off with the aluminum rod. You already have an out of the box, basically one off combo which could end up working really well. It would probably be better off for you to go with what you know will work because if it doesn't you are out a lot of money and the ability to replace what you have might not be easy. One less worry so you can get out and test, I know I have been following your build and am really interested to see how it works.
 
#21 ·
steel rods would work fine if the tune up is there, keep an eye on the bearings. its not on nitro so the cylinder pressure is reasonable still. soon as you add the pop the bearings turn to hell with steel rods... we do a H.D rod in billet 4340 with the radial beam for these types of builds all the time.2.100" whatever you like...the real qustion is the crank , might needto get you on one of those when the time comes. youll spend 5k for crank and rods but will only do it once.
 
#23 ·
Carrillo is also and excellent choice for custom rods
 
#24 ·
I have a 540ci BBC talldeck with a HTC crank 4.250, 6.385 carillo rod(which need changing) wiseco flat top pistons. I am looking to make 1000hp with NOS and spin the engine at a limited 8500. Is it neccessary for me to buy alum.rods for this engine? If so will I need to change them every 100 runs (I am working with a small budget)? I have spun bearings on this engine and I am thinking this rotating assembly is too heavy so I need you all expert opinion so HELP?! (please)
 
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