LIL SS

iTrader: (9)

So on my 418ci motor in my truck, I do not run anything but an alternator. Is there a pulley out there that is made that only has the front belt grooves? I'm thinking there is rotating weight there I don't need.

I currently have a Camaro ASP UD Pulley so I'd prefer to keep the same belt depth but not afraid to move my alternator forwards or backwaeds if needed.

Damian

iTrader: (89)

FWIW, the pulley has to be a certain weight and design to properly balance the engine. I don't think you're going to find what you're looking for without throwing off the harmonics of the bottom end.

Not to mention, shedding 1-2lbs off the crank pulley is not going to make a noticeable difference on a 418ci motor.

djfury05

iTrader: (30)

Isn't the only thing that changes with an underdrive pulley is the diameter itself, which in turn helps the motor to spin faster. The weight should be the same as stock because its a balancer to the rotating assembly. You aren't going to benefit any by findiing one with no grooves for the a/c.

Beau@SDPC

iTrader: (14)

The only ones I have seen are the ATI balancers. They are alot more $$$ than the ASP you have now, but are ALOT better than ASP as well.

LIL SS

iTrader: (9)

Never realized they needed to be a certain weight to "balance" the harmonics. Just thought they needed to be balanced since the motor is internally balanced. Obviously an out of balance pulley would cause a bad harmonic and probably beet the snot out of crank bearings and timing set.

So if what you are saying is true, ALL the crank pulleys are the same weight aftermarket or factory? I think I'm going to have to check that out next time I pull my ASP off as I have a factory pulley for both a vette and F-body.

If that's the case, I might see about a 25% reduction pulley if I do buy a new one since I don't really drive the truck on the street..

LIL SS

iTrader: (9)

I know my stuff is internally balanced. The idea of the crank pulley keeping balance does not make sense to me. Here are some reasons why:

1) I doubt Truck, F-body, and Vette crank pulleys are equal in weight. Perhaps self balanced but not identical in weight.
2) If the crank pulley had an ill effect on the "balance" of the motor, wouldn't a SFI aproved flexplate that is typically thicker and weighing more mess up the "balance" in the same effect. Yet as long as the flex plate or flywheel is balanced, well, you can change them in and out as you pleat. Not to mention converters and clutch systems that all weigh differently.

Roatational weight is power, period. Even if it is 3lbs in a 8" circle. Understandably less than 3lbs in a 12" circle, but it requires energy to spin its mass. Every little bit helps.

I understand the crank pulley has a function, but I believe that function to mainly be running the accessories and isolating the harmonics caused by them. So with that, the weight of it, diameter of it ect would have no effect on "balance" of the motor. But I don't know this for sure. That's why I'm asking the question.

Beau@SDPC

iTrader: (14)

A torsional dampener does not dampen harmonics from the water pump. Check out that phrase on wiki or something, you will see what it means.

Also there are alot of interesting reads about guys with the SBC engines going to a larger balancer and having no ill effects from it, but also reporting gains in different areas. Meaning going from a 6 3/4 or 7 to an 8" balancer. Its available to read if you search just right.

FYI lightweight flywheels and clutches can cause a whole other mess of problems too, and so can super lightweight balancers on the front of an engine. Mass is a factor, but there are other forces at work as well. Its not 1 dimensional.

LIL SS

iTrader: (9)

John,

I can see an arguement that heavier can be better in some places too. IE a clutch car that needs to 60'.. The heavier pulley, clutch and flywheel might help keep the revs up when the clutch is dumped since there is more rotating weight to slow down in the first place. Perhaps it would benifit me on the 60' to have the heavier mass as well just to get my brick rolling all though I run a high stall (Even higher now with the glide going in). But with that, perhaps ET or MPH would suffer. I have no real answer and wouldn't unless tested. But that is what makes this sport fun. Trying new things and experimenting.

Another thing, the only thing I am running off the crank is the alternator. With that I don't even loop it to the idler pulley on the electric water pump..

Beau@SDPC

iTrader: (14)

I am not just talking about racing. I am talking about normal street driving and tuning as well.

Its not all about the weight being a factor against the application. Sometimes it helps.