I am looking at building a long rod 2.0 for my 57 trim witch will turn into an hta35r sometime in the next 2 years. Looking to put out 500ish on the 57 and 600-650 on the 35 (both on e85).

Would you recommend alum. rods for this kind of build? Will the possibility of having a lighter piston have any effects on the aluminum rod pro or con?

Thanks

 

SILVERnSLOW- I would only because I dont like to see people spend money twice on parts of engine rebuilds. If you intend to step the car up to 600+whp with an ultimate goal of 650 or so I think your bearings and overall engine life will be greatly enhanced. 156mm 2.0 will be pretty cool by itself. I get stoked hearing about all these non-typical builds.

 

What if you were building a 2.6L with really high compression, 10-11:1, and high boost, 40-50psi, with the rod angle and increased cylinder pressures would aluminum rods be strong enough? It seems like for strokers something like carrillos or pauters would be better than bme and grodens with the opposite being true for 2.0L and 2.1L. Confirm or deny?

 

Are Aluminum Rods able to handle the extra compression type loads of a stroker?

 

Cant wait to build my motor w/ these rods Aaron.

 

They handle 1400whp so I doubt there is much you can throw at them that will make them just break. The lighter weight is ideal in a stroker becuase you are talking about reducing reciprocating mass which frees up the engines ability to rpm (or in english frees up hp). Remember these are the rods that are in TOP ALCOHOL and TOP FUEL, I am pretty sure our stuff is covered under that umbrella

It still comes down to things like bearing life, reciprocating mass, etc.

I am curious why you are building a 2.6 that will see 50psi? Honestly you will have lag no matter what so opting for a better R/S ratio of the 2.4 is a better way to go, if not something like a 2.3L 4G64.

 

Brent Rau likes these rods

 

Exactly

 

IIRC, one snapped in half on him, wreaking the usual havoc.

When it comes to attempting to gauge the service life of the rods, I'm not certain that checking for stretch is a viable/reliable indicator. Those rods do continually stretch and compress while the engine is running. This is why engine building guides will typicall advise to increase piston/head clearance by 40-50% more than an equivalent steel rod engine. If pistons begin to kiss the heads, it's curtains.

Aluminum rods definitely have advantages and disadvantages, just like anything else. I remain highly skeptical of manufacturers' claims, simply because they produce no data pool, no statistics, and since they can't really be held accountable, they're free to say pretty much anything they like.

Ultimately, it boils down to what is practical and financially acceptable to an individual. Regardless of what's claimed, I would advise changing these rods at regular intervals. I would advise the same for the rod bearings for high HP steel rod motors that are expected to last (DD applications). For me, it's far easier and more cost effective to change rod bearings than rods. Those with unfettered access to a specialized shop, low cost expertise and labor, and parts at jobber cost are likely to see a different range of practicality than most.

 

^ nice

 

Those engine building guides i beleive are more geared toward v8's.. From my experience a tiny 85mm piston doesnt cause as much rod stretch as a BBC will.. Taking that into consideration i still believe that aluminum for big hp has more advantages then disadvantages.. I havent seen an aluminum rod fail as of yet.. I have seen wreckage due to other failure but not rod failure being the cause of the wreckage..

Mike

 

Right here Mike:

https://www.evolutionm.net/forums/5801773-post1.html

I understand your point about the smaller mass piston not creating as much force (which ultimately stretches the rod). I would think that the mass of the rod would (or should) be sized with approximate piston mass taken into account. Maybe they do this or maybe not, I don't know.

Again, I'm not arguing the virtue of an Al rod, I am questioning the practicality of changing the rods at periodic intervals vs changing the bearings. I'm not questioning it from a vendor/drag racer point of view, but from a retail consumer/daily driven transportation point of view.

For those who may find it interesting, here are some average rod masses for common 4G63 rods. These are for a 6-bolt 4G63, but I'd expect the 7-bolt figures to be relative:

Stock = 695 grams

Aluminum:
GRP = 470 grams
Map = 470-480 grams
Groden = 490 grams
R&R = 500 grams

All other material:
Crower titanium = 410 grams
Carrillo = 520 grams
Engine pro = 557 gram
Manley H beam = 573 grams
Eagle = 575 grams
Oliver = 605 grams
Pauter lightweight = 610 grams
Crower = 612 grams
Scat = 640 grams
Map billet rods = 652 grams
Pauter = 685 grams
Manley I beam = 690 grams

(from DSMtuners.com)

 

Maybe i should have specified better.. of course i am aware there have been aluminum rods that people have broken.. I personally havent seen a failure myself on any of my motors.. My little RS that ran 8's is still getting beat on weekly on the streets today.. The picture of Al's broken rod could have come from any failure in the motor. I am not sure if he determined the exact cause or not.. Also, i might be mistaken but i believe he had re tq'd those rods more than 1x also.. Unless i see the failure for myself on something we have assembled and tuned here i dont see any drawback to the aluminum rods yet..

Mike

 

Sure, but the only thing that can prove anything for certain is the passage of time. Not a few passes at the track, not a few months of use, not a few thousand miles. Why? Because time (specifically heat cycles) is the thing that eventually fatigues aluminum to failure. When she goes, nobody really knows, and that is the issue at hand.

 

Well I think there have been 12k miles logged atleast on an aluminum rod motor and its still running so thats good sign.. Id never really expect 12k miles out of a race motor that sees 50-60psi.. Thats a lot of street driving and track use.. In most cases you go to aluminum rods for a race motor not for longevity of street use.. So if its 2k heat cycles before they lose shape and break i can handle that..