Question about lightweight pistons/connecting rods

[JAM]

I did a search and couldn't find anything to answer my quetsion. Has anyone here tried using alum lightweight pistions, connecting rods, etc? If yes, did you gain any performance from it?

[WickEdSix9838]

you wont gain hardly anything from doin that unless you go with more compression, and about the aluminum rods, they arent made for street cars, they are for all out race cars, one reason being they have to be changed WAY more often, in my dads race car we run Groden aluminums, they have to be changed after about 150-200 passes, along with the main/rod bearings, rings, and a new hone job, they cost about $800-$900 for a big block chevrolet set....

[JAM]

Ok so if I mill the heads to get higher compression and increase the bore using alum pistons, and leave the connecting rod alone. Any advise on that type of set up?

Just trying to think of ways to get more power without destroying the normal day to day drivability. I know there is always some risk assocated with any change. Just looking to minimize that amount of risk.

Please advise. [img]smile.gif[/img]

[CartmanSS]

If you are looking for cheap horsepower, hook up a nitrous system.

Replacing the pistons and rods will not increase horsepower - they cost a lot to replace, and a modest V6 like the ones in our cars won't see any advantages.

[JAM]

No such thing as cheap horse power it all cost $. :D Just looking to have less rotating mass and friction. But seems like what I am hearing is that this makes the car un-reliable?

[12secondv6]

Not yet but I am building a stronger engine this winter.
Any reduction of rotating mass free's up hp (a very small amount).
Technically reducing rotating mass can also improve gas milage.
I used a search engine for a while but I can not find concrete proof for ya.

[JAM]

James that would be interesting to find out. I'm sure you would get some advantages out of it. Doesn't seem like anyone has tried it yet. [img]graemlins/burnout.gif[/img]

[TheFireChicken]

A lot of people have a common misconception about aluminium. They assume that it is stronger than steel or as strong as steel, but its not. Aluminium is actually much weaker than steel. The reason its used for things like wheels, and aircraft parts, is because aluminium has a density that is about 1/3 that of steel. That means that if I have 2 identically sized blocks of aluminium and steel, the aluminium block weighs about 1/3 of the steel one.

Aluminium is used because its a lightweight material. However, for lightweight materials, your other options are plastics, titanium, carbon fiber, fiberglass.

None of those are really strong. So aluminium is the strongest of the "light weight" materials, but in a strength comparison of other materials, its pretty weak.

Also, you need to understand something about stress. Anytime you apply a force to an object, you are applying stress. When stress is applied, a certain amount of permanent damage is done to the material to weaken it. The rate at which the material weakens with respect to the amount of stress it has endured is a constant number, that is different for each metal. Aluminium has one of the highest amounts of damage per unit of stress of any metal. That means that aluminium will weaken faster than steel in identical circumstances. That is why aluminium rods are used in race cars. They are very light, but they also degrade and require replacement very quickly.

[Slow-N-ugly]

I agree with 12secv6 Any reduction of rotating mass free's up hp (a very small amount). The key word is FREES UP. The noticeable advantage would be spinning your motor up into the powerband. A lighter reciprocating assembly will get to 4200 rpms faster that a heavier one. There is a thing called Parasite drag, that is anything that slows down a moving object. In the case of your motor it is your rotating assembly, including your flywheel, and oil (Ever heard of a windage tray)? It is also the idea behind removing an AC compressor or the alternator.