[Sub Boy]

Why are I-Beam Rods more expensive?
Why bother making H-Beams if the I-Beams are better?

:nervous::nervous:

 

[icydude]

H-beams are typically stronger but heavier. Your typical h beam will resist bending better at the same weight as compared to a i beam. it's all about cross sectional width.

much like driveshafts being hollow, outside diameter determines strength more so then thickness.

f1 rods are a mix of h and i
http://i25.photobucket.com/albums/c60/jrobson_1/DSC00063.jpg

http://www.pankl.com/uploads/pics/engine.jpg


these are out of the old cosworth v8's much like our rb h beams
http://www.schuerkamp.de/zope/hoover/racing/historic_f1/images/lsm06_pistons.jpg

 

[Jimbostir]

"H-beams are typically stronger but heavier. Your typical h beam will resist bending better at the same weight as compared to a i beam. it's all about cross sectional width."

Text book answer there!

 

[JD74]

So, if a set of Carrillo Pro H's for RB26 are 507 gr......and my Manley Pro Series I-Beams for RB26 are 610gr.........which are stronger ?
since it's only the H that is stronger at the same weight ?

 

[icydude]

So, if a set of Carrillo Pro H's for RB26 are 507 gr......and my Manley Pro Series I-Beams for RB26 are 610gr.........which are stronger ?
since it's only the H that is stronger at the same weight ?

the i beam you bring up in question has a lot of bling bumps on the bottom

It depends on the thickness of the manley rod in the center. It's possible they are equal in strength but we have no test data so who knows.

 

[JD74]

Yes, I will admit, they are a little bottom heavy.

My average weights are 425 big end/small end 185 (=610gr) on each box within .5gr either way.

 

[GT-R Glenn]

Actually define stronger...
Longitudinally
In compression / torsionally ?
The H is stonger in a bending moment through the two beams.
The most important factor for the rod would be in compression as, correct me if Im wrong that where most fail.

 

[Sub Boy]

So if one was to want to run higher than std compression and rev to 9000k on a RB30....? what's going to be better suited?

 

[GT-R Glenn]

Well, what shape are the factory rods ?
We know that they will support 700/800 hp

You want the rod that is the stiffest ...
And cross sectional area does not automatically equate to stiffness.
Shape dictates that and that would be assuming the exact same material is used with the exact same properties.

H beam I think are slightly more forgiving before they fail.

pauter are x beam btw ...

 

[GT-R Glenn]

Sorry, forgot to answer
Argo I beam rods....
Ask Rob he has a lot of first hand experience with the exact subject....

 

[Sub Boy]

Cheers Glenn,
So if I was going to lower my sights to 7500rpm-8000rpm and had a choice of either keeping the factory rods (shot peened and linished) or a set of cheepie Eagle rods.....?

What is the RB26 rod pin dia? 21mm or 22mm?

 

[infamous_t]

or a set of cheepie Eagle rods.....?

Wouldn't be 6" chev rods your getting cheap by any chance?

 

[Sub Boy]

Wouldn't be 6" chev rods your getting cheap by any chance?

:chuckle: Yes....Should I know something about them?

 

[infamous_t]

:chuckle: Yes....Should I know something about them?

Thought so.

A fellow on SAU is in a similar position to you (access to v8 teams gear)
This thread has pros/cons and what needs to be done
Chev Small Block - Skylines Australia

 

[JD74]

What is the RB26 rod pin dia? 21mm or 22mm?

21mm stock.

 

[GT-R Glenn]

There were some chev rods for an RB30 on trade me ....

 

[nismodude]

Std rods

Well, what shape are the factory rods ?
We know that they will support 700/800 hp

You want the rod that is the stiffest ...
And cross sectional area does not automatically equate to stiffness.
Shape dictates that and that would be assuming the exact same material is used with the exact same properties.

H beam I think are slightly more forgiving before they fail.

pauter are x beam btw ...

Glenn if I may ask I belive you sad in another treat
if you replease the rod bolts with arp ones you can run
600 hp easy?

 

[Chris Wilson]

Actually define stronger...
Longitudinally
In compression / torsionally ?
The H is stonger in a bending moment through the two beams.
The most important factor for the rod would be in compression as, correct me if Im wrong that where most fail.

Rods usually fail in tension as result of trying to stop the piston hitting the head at high RPM. Compression loads are pretty easily assimilated unless you are looking for the ultimate in lightness at modest RPM'S.

Although the stock RB26DETT rods are strong they use a rather dated method of retaining the big end caps, bolts and nuts. I personally think a lot of RB rod failures are really bolt failures, it's very easy to install a shouldered bolt into the main part of the rod wrong, and either nick the corner of the rod to leave a stress raise, or to install the press fit bolt wrongly clocked, so the oval head is cocked around and not sat securely on the flat of the rod. In use the rod bolt rotates a fraction to fully seat, and loses tension, then BANG! Modern thinking, save in Ti rods where bolt galling is an issue, is to use bolt that threads into a female thread form in the upper part of the rod. These are inherently more reliable as you lose half of the interfaces.

 

[GT-R Glenn]

Rods usually fail in tension as result of trying to stop the piston hitting the head at high RPM

Shit, typo.. my bad ... downshifting ....

yes I run factory rods, shotpeined with 300zx tt arp rodbotls and nuts
its about 670hp at the engine

 

[Sub Boy]

There were some chev rods for an RB30 on trade me ....

That's what made think of the Chev rods I can get, They will require some mods (I asked the guy that was selling them on tard me)

...Still will be better than some old factory RB30 rods...Yeah?