aluminum or steel connecting rods???
 

I am looking for help on connecting rods. I currently have a custom set of Bill Miller aluminum connecting rods that are going into a 460 stroker. My engine builder is extremely concerned about using them. He feels they are an inferior rod when compared to steel (he is also possible stuck in the olden days).

My cobra will be a weekend driver going to occasional road races. I would like to use to aluminum rods.

Any information good or bad would be very helpful.

This is a very good question. I see those beefy Manley aluminum rods made for race/competition in the Summit catelog and always wonder the same thing. I will be interested to hear a good answer.

Ed

Seriously limebluie,

Didja ask Bill Miller that question? My engine builder uses aluminum sometimes for drag racers - not in any engine intended for other kinds of uses.

I've always "heard" they don't have the longevity (fatigue life?) for street use.

Let us know what Bill says!

Tom

Hello again limebluie,

Here's the Bill Miller contact info:

http://bmeltd.com/contact.htm

The only applications I see for those aluminum rods on his web site are for drag racing. He has pistons which are used elsewhere.

If you want a thrill, read his rod maintenance instructions!

Enjoy, and tell us what you found out!

Tom

Yes, I talked with Bill Miller on multiple occasions. They said there aluminum rods would out last a stock steel rod. They also told me they have many street cars with there rods. Whenever I talk to them they make it seem like I am an idiot for asking. In there minds there is no reason not to use there aluminum rods.

Aluminum rods will certainly outlast "stock" rods. Aluminum rods are beefier becasue they don't have the strength characteristics of a steel rod of the same size. If you're going with a stroker, be careful that the rods don't hit the block. Big stokers sometimes require notches in the block for them to fit.

Personally, I'm going with forged H-beam rods that will outlast those aluminum rods. And, steel doesn't have the large thermal changes that aluminum rods do.

Venom_S :3DSMILE:

About the only application that requires aluminium rods is for nitromethane. There the material is needed as a shock absorber for the bottom end. Their life span is a short one though since they work-harden, losing the properties for which they are needed.

Another reason to use aluminum rods in race only applications is reduce rotating mass. High reving engines need to rev higher faster than a street machine. Aluminum rods were never intended for daily use.

Use a high quality H-beam that has been shot peened, and magnafluxed. You can't go wrong with them.

Venom_S

This is so right.

I know you want to use the AL rods because you have them already, but the same effect can be had other ways.

I went with Crower rods. Heavy right? Not once I changed to longer rod length and shorter, aluminum pistons. The rotating assembly LOST weight overall. Then if you spend time on your crank, you can lighten that up considerably.

The goal is to lighten up your rotating assembly, but not to the point where you're constantly wondering when it'll let go...today, tomorrow, next lap.

The other consideration is clearances, as has already been brought up, though not just in the block/rod area, but in the head/piston area as well. AL rods will stretch more at higher RPM's than steel rods and you need to make sure the valve-to-piston clearances are sufficient as well.

I'd vote for non-aluminum rods. You know Crower makes titanium rods?

Aluminum Rods
 

Aluminum rods grow with age and use and have to be re-sized every 15k miles or so with street use. What a pain in the a*s ! They can be resized about 5 or 6 times then you will have to throw them away. I have said this before , listen to your custom engine builder. Most times they really know what works because they have been there. Most times they don't know how to read those hot rod magazines that get 90% of enthusiasts (myself included) into trouble.
If you haven't got your crank yet I would also look at the so-called Chevy setup. Smaller, lighter , cheaper rods, smaller rod bearings means more power. If your builder is worth his salt he will know what I am talking about. It will cost a bit more because of the higher crank cost but it is worth it.
I don't know much about titanium rods other that a few years back they were used to build Nascar qualifying engines. Seems they clearanced the bearing really sloppy for more power and the rods would hold together long enough to qualify the car without stretching. Today they are illegal to use I think.( I don't know) I hear that they have similar propertys with aluminum rods. Maybe someone else can tell us how they fatigue along with their propertys. I can tell you, titanium normally has low lateral strenth. Like a pensil it will snap in the middle easy but has superior strenth when compressed. (like on a rod)
Now repeat after me. STEEL RODS, STEEL RODS, STEEL RODS.:3DSMILE: :3DSMILE: :MECOOL: :MECOOL:

COBRASHOCK

Aluminum work hardens at a faster rate than steel. That is the more stress cycles aluminum is subjected to the more brittle it becomes. I have had experince with aluminum rods in stock car racing years ago, learned that aluminum rods are for drag racing not for any long term stress. Listen to your engine builder , unless you would like some new inspection holes in your block. :CRY:

More from Bill Miller (2nd hand!):
 

Hello again limebluie,

Here's yet another perspective on aluminum rods. It's from another forum, and the author is quoting (paraphrasing?) Bill Miller hisself about the life of aluminum rods.

http://www.network54.com/Forum/messa...eid=1011293411

I guess the bottom line is whether you plan to put enough miles (and/or passes?) on the engine to warrant rebuilding it rather often.

Hope this is at all helpful,

Tom

I considered aluminium rods, but as stated, many drag racers swear by them FOR RACING but say that they are not good for street cars.

The aluminium rods offer superior performance but they become brittle and can snap after some period of time...

A good Carillo (or equiv. I think I have Eagles) rod is enough for the most wild street motor. Now, if you want a race motor in a street car, then that changes things (including your maintenance schedule).