Mighty Whitey

A few years ago I had a guy give me A stock harmonic balancer and, and asked me to machine off the a/c belt grooves off the back side of the balancer.

I chucked it in a lathe, indicated it in ,and machined off what he wanted and gave it back. He weighed it, said I removed around 4lbs of material, put it on the car, and said it made World of difference in how quickly the car revved considering all he is turning is te water pump and alternator.
This was back in late 2006, going on a forged 347. After roughly 100lbs of nitrous, numerous runs down the track in excess of 7200rpm (a couple accidental 7600 rpm runs) and a pile of mid 9sec timeslips, it's still going strong.

Has anyone else done this, or Thought of doing it? If his motor lived to regularly see 7200rpm shift points and held up, it can't be that bad, and a very easy means of getting rid of 4lbs of rotating mass.

djfury05

iTrader: (30)

never heard of it.. too much weight off could cause a problem to the balance though.. sounds like just enough was taken off to make a difference and remain in balance.. pretty sweet

BIG_MIKE2005

iTrader: (116)

As far as I knew it shouldnt matter cause the LS1 engines are internally balanced not externally.

Someone correct me if I'm wrong.

Sales2@Texas-speed

iTrader: (5)

If it was ground down unevenly it would still wobble on the front of the crank and cause problems, despite the engine being internally balanced.

BIG_MIKE2005

iTrader: (116)

Good point. didnt think about that when I posted that, was mainly meaning for the weight removed from the pulley when done having any effect on the balancing.

I just "assumed" if it was machined down properly everything would be symetrical & not outta round when finished. I should know better than to assume by now, LOL.

Sales2@Texas-speed

iTrader: (5)

It's a hard lesson to learn, but internet forums help teach that lesson for sure!

Mighty Whitey

grinding? What exactly are you refering to here?

I chucked on the ID of the "hub", indicated within .0005" TIR on the seal surface AND the ID of the crank hub (where the crank snout goes through) took a tungsten carbide turning tool insert and let the cast iron grains fly!

I was under the assumption that an ls1 is fully internal balanced, meaning the "balancer", is really just a harmonic dampener, so any material removal would just mean a lighter rotating Assembly.

Basically, to remove 4lbs off of the rotating assembly would require a crankshaft with profiled counterweights, cross drilled crank throws, and or gun drilled mains, assuming you can even do that. A crank like that would cost atleast $1500bucks i would think.

Not sure if it's worth anything in the power dept. Or not, but it makes for Bhell of a conversation piece when you pop the hood around other lsx afficianado's and they notice it.

Gary Z

Weight removed from the damper pulley will not make a noticeable difference in how quickly the engine winds up - the pulley radius is too small to have a significant flywheel effect.

Mighty Whitey

I was a little skeptical about A day and night noticeable difference myself, just putting out what the "customer feedback" was, that's all.

Rotating weight is rotating weight no matter how you slice it, I'm sure it's bound to help somewhere along the lines tho.

The_Rizzle

iTrader: (4)

Yes it will. Thats right around the rod throw radius. And the weight is on the outside of the pulley. It will make more of a difference in the car in lower gears, since the engine is revving up faster.

EDIT: I was also considering doing this on one of my buddies (budget) race engine.

orangeapeel

iTrader: (18)

This thread would be better suited in the External section vs Internal. Moving thread.

Sales2@Texas-speed

iTrader: (5)

I am not saying you did not turn it accurately or without precision...I was simply pointing out for Mike that if turned down unevenly it would cause an issue. Congrats on having the guts to try this, most wouldn't think of it, much less attempt it!

Gary Z

It won't make a noticeable difference in any gear or in neutral. Rotational inertia is proportional to the square of the radius. That is why pure flywheels have their mass concentrated at the rim. Eliminating the damper pulley would not noticeably change the total flywheel effect.

Mighty Whitey

I gotcha... I'd say an improperly turned dampened would wreak havoc on the rotating Assembly if it was more than .0002" out, especially on an eccentric.


Gary Z:

I understand the fywheel effect, and that the inertia is greater on aarger diameter wheel than a smaller one, but regardless of the size of A wheel, even if you take all of the mass out at the center of the hub, that is still xxx amount of weight that doesn't have to be moved, which means less work exertedto get something rotating.

Go roll a 1foot piece of 6" roundstock on the shop floor, then roll a piece of 6"x1.00" wall tubing of the same length across the floor. Then tell me which one you had to exert the least amount of energy to get moving, and which one you had to exert the least energy to keep moving, and which one you bad to exert the least amount of energy to get slowed down, or stopped.

I'm willing to bet you'll find the tubing requires much less energy to change whatever state of motion it is in. But how could that be? Assuming something of that small of a diameter could not have a measurable difference of inertial force? Every bIt of the material removal is right at the center point too. Just imagine if you shortened the overal length of the tube by 40% and compared it to the original tube in regards of energy exertion. (same thing as my proposed material removal from the dampener)

Not to be an ***, but to say that there is no effect on inertail force by removing weight from a part that is only 6 or 7" in diamter is a little far fetched.

A rod/piston is going to exert the same amount of force on the crank regardless of what is attached to it, the less rotating mass there is, the easier it is going to be, for it to do what it wants, in this case: acceleration.

If it does nothing for me, it's still 4lbs off the nose of the car, weight reduction is like free horsepower...

01ssreda4

iTrader: (96)

OP, If I was in your friends situation I would definitely have asked you to do the same thing. Eliminating 4 pounds of spinning weight will make the motor rev slightly quicker. I know bc with an aftermarket converter 35 lbs. vs. stock 50 lbs, its night and day difference.

joecar

+1 what he said ^

rotational inertia is proportional to mass and radius squared: http://en.wikipedia.org/wiki/List_of_moments_of_inertia

angular acceleration is inversely proportional to rotational inertia: http://en.wikipedia.org/wiki/Angular_acceleration

How much difference does 4 lb make...? Not as much as 15 lb, but it still is a difference (every small bit adds up).

S10xGN

iTrader: (11)

I've been looking for a cheap C-5 balancer to try this with, as my S&P A/C setup runs off the front (normal) set of grooves. Mainly for looks, but also for the weight...

180ls1

iTrader: (4)

i wouldnt risk it

nysbadmk8

Awesome idea.. But I like my a/c

Damian

iTrader: (89)

While this is true, screwing with the weight of the pulley in any way can cause problems with timing chain harmonics. For example, a lot of the Corvettes are breaking timing chains because of the balance issues with the ASP pulley design for that engine.

I wouldn't manipulate the pulley in any way. It is what it is, and the gains are going to be negligible at best in comparison to the risk taken.