I know it has the timing mark on it, but aside from that, can you?

Yes, but...
Is it a V6? If so, I would get a replacement as soon as possible.
A 2.5 originally had just a hub and pulley, they added to it later, but I would replace it too, if it is missing the dampener.
It is up to you, but I wouldn't even run it if it is missing. It reduces vibrations that can cause problems.

yes its a v6, but does it really matter? what damage can it do?

quote Originally posted by AL87: yes its a v6, but does it really matter? what damage can it do?

CAN you? Sure..the engine will run just fine without it. SHOULD you? Only if you're OK with potentially snapping a crankshaft.

Each time a cylinder fires, it imparts torque into the crank, causing the crank to deflect/twist a small amount, then snap back, much like a rubber band. At certain engine speeds, this can set up a harmonic, which amplifies the effect, and potentially pushing the crank to failure. The harmonic balancer absorbs these deflections of the crank, preventing failure.

Without it, cranks can and do break, usually before you even realize what's happening.

quote Originally posted by AL87: what damage can it do?

quote Originally posted by urbex: Without it, cranks can and do break ...

Yep. That's the whole purpose of the harmonic balancer ... to damp crankshaft torsional vibrations. The outer rubber and steel rings are what perform that important damping function. The HB is "tuned" to each specific engine design and configuration (e.g. crankshaft torsional stiffness, number of cylinders, spark or compression ignition, max cylinder pressure, operating rpm range, etc.).

[This message has been edited by Marvin McInnis (edited 07-18-2012).]

I have seen a lot of circle track guys remove the outer ring on the SBC balancers to reduce rotational weight and improve acceleration coming out of corners, but then again the circle track engines have a much shorter (although much more abusive) lifespan than a daily driver.

Also, if you look at the lifespan of an engine family (like the SBC) you will find 10+ different versions (shapes, sizes, weights, and styles) of the harmonic balancers over the years with people routinely swapping them for their particular application and running them for years and thousands of miles without issue.

For example, the 88 2.5 in the fiero used a stamped steel serpentine pulley (probably less than 1 lb total) without any signifcant weight or isolated dampener. The 89 2.5 FWD engines have a legitimate pulley/balancer setup with a rubber isolated outer ring (with the serpentine pulley integrated to it) and weighs about 5 lbs. Both engines are very similar, but neither are known to have had crank snapping issues and both have examples of lasting 200K miles.

I do believe having an optimally matched balancer is ideal for longevity (200+K mile life), but if the balancer is off 1 lb (or 1" in diameter) from ideal, does that shorten the life expectancy 500 miles, 5000 miles, or 50,000 miles vs. the 200K original life? If it is 500, 5000 or possibly even 50K miles, then how critical is it, if the engine will still will run for 150K miles without snaping the crankshaft? So in the end, I am not really convinced that a change in harmonic balancer size, shape/weight has a significant impact on engine life.

okay, what if I upgraded the crankshaft?

The balancer should be matched to the crankshaft. Different crankshaft => possibly different resonant frequency => different harmonic balancer.

Why is resonance important? Think of the classic example of an opera singer breaking a wine glass by singing a single note for a few seconds. Why is damping important? Think of a large bell ringing. Now think of that same bell with a heavy rubber (or lead) blanket over it. Think of the wine glass wrapped in a cloth napkin.

[This message has been edited by Marvin McInnis (edited 07-19-2012).]

Been running my 2.8 for years now without the weight.... But then again, I have a 3.4pr setting in the corner to replace the high-mileage motor.

quote Originally posted by AL87: okay, what if I upgraded the crankshaft?

Why are you so intent on not running it? If you're thinking the engine is going to accelerate quicker without it, you'll never see a difference with or without.