Both "I" and "H" beam designs have their strengths and weaknesses. Quality of the metal, grain structure, consistency, purity is important. Design of the part is also important and any imperfection becomes the weak link where a failure can start. Rod bolts are also critical as is INSTALLATION, proper stretch and proper clearances.
A quality rod of either design will handle the power output of most street efforts.
All the above in consideration there are definite benefits to light weight. Less weight is less stress as RPMs rise. Unnecessary weight is of course unnecessary.
I would like to price a set of those in the correct size to combine a stroker crank with a 3UZ block.
What type of material is your rod manufactured from?
Each and every Oliver connecting rod is manufactured
from American made 4340 aircraft quality steel
produced right here in the USA.
Can I use an "Ultra-light or do I need a "Standard weight"
rod for my application? As a rule of thumb if your
reciprocating components such as piston, wrist pin,
and ring combination are of lightweight construction and the
acceleration rates in your given application are quite high
then you may favor a light connecting rod.Always take the
safe route when choosing a connecting rod based on
weight if applicable. Cycle life diminishes as you take
away cross sectional area in any component whether
it is a connecting rod, piston, crankshaft, etc.
BE SAFE-DON'T BE SORRY!
What rod length is best for my application? Each engine application is different based on engine
modifications for your particular type of motorsport and
the RPM range where it will function the majority of the time.
Forced induction applications sometimes are limited on
choices relating to piston configurations. Have you ever
assembled an engine with too much cam timing?
The same applies to many applications when
it comes to rod length!
What rod bearing clearance should I run?
This is one that has the general rules that have been
learned though years of experience along with special
applications. Competition engines generally are looking
for clearance in the .0025 to .003. Some smaller journals,
2 inches in diameter and smaller may run slightly tighter
clearance of .0022 to .0025. Large journals 2.200 in.
diameter and larger might run slightly more clearance of
.0029 to .0032. Blower motors that tend to build a lot of heat in
the bearing will run clearances of .0032 to .0035 with a
heavy weight. The extra clearance lets the oil flow easily
to help cool the bearings while the heaver oil helps cushion
the load. Small journal cranks will have a slower bearing
speed and can run lighter oils with tighter clearance
of .0020 to .0023.
Do I need a bolt upgrade for my application?
There are several factors to consider in determining whether
or not to upgrade bolts. They all come down to tension
load—the more tension load the engine has experienced,
the more you'll want to consider upgrading your bolts.
Tension load is the result of reciprocating (piston, pin, rings,
locks, bearings, rod weight and stroke) weight
versus RPM. Light reciprocating components and short stroke
cranks create less tension load. Heavy reciprocating components
and long stroke cranks develop more tension load.
How the engine is used also plays a big part. Circle track and
road racing use the engine to "brake" into a comer. When closing
the throttle at max rpm this exerts an abundance of tension load
not only on the connecting rod but also on the fasteners.
It mostly comes down to the way the rod loads and unloads, an I beam rod will be stronger on the compression stroke, but if you maintain too heavy a piston/pin combo, excessive stress occurs around the bottom if the small end bushing.
Conversely a H-section rod will be less resistant to the buckling moment of the compression stroke but will be stronger around the pin.
And this is where you need to decide your application and then choose your rods.
However i have to agree with JBrady where you can have the most effective design in the world, but if its installed incorrectly its still toast.
Oliver rods are a Parabolic I-beam, which means they look less like an I-beam and more like two 'U's facing away from each other. They claim to be analysed using Finite Element Analysis which give them an excellent design with no apparent stress concentrations but I dont think ive seen enough of them to compare to comething like carrillo.
Generally speaking, an I beam is better suited to a forced induction motor, not seeing atmospheric RPM's, and the H-beam better suited to an atmo motor that turns a bit quicker.