Crank pulley

[bentandbuzzin]

I noticed when i pulled my crank pulley to do the timing belt replacement the center groove section for the a/c belt moves freely. Is it supposed to do that? I thought the pulley was all one solid piece. To make this clear...i can hold the pulley in my hand and spin the center section like a wheel. If this is not right i think i may have found my problem with trying to get the timing mark to stop rotating around when i put the timing light on it.

[evildky]

uh oh! nope it's not supposed to do that, sounds like your ballancer has gone bad, replace it! do not put that back on the car! you're gonna need a new ballancer

[DanDrath]

time for an upgraded under drive pulley

[NORCAL300ZX916]

on the ac pump or the crank pulley? the ac pump should do that. i dont understand how the main/crank pulley could spin with out being broken in two.

[bentandbuzzin]

uh oh! nope it's not supposed to do that, sounds like your ballancer has gone bad, replace it! do not put that back on the car! you're gonna need a new ballancer

I already put everything back and i was trying to set the timing. I didn't think that was right so i guess this is why the timing mark rotates counter clockwise when i have the timing light on it. I set the idle at 700rpm and even lower and the mark still moved but took forever to return to the top. Thats when i remembered about the pulley. I will get that off asap before it destroys all my hard work. Thanks for all your help evildky and everyone.

[bentandbuzzin]

on the ac pump or the crank pulley? the ac pump should do that. i dont understand how the main/crank pulley could spin with out being broken in two.

The problem is with the crank pulley on the center section where the a/c belt goes not on the pump but on the crank pulley.

[bentandbuzzin]

time for an upgraded under drive pulley

Should i get one or just find stock pulley. What is the advantage of an underdrive pulley?

[NORCAL300ZX916]

i was going to my local z specialist and he cautioned me against the underdrive pulley due to its lighter weight it lacks dampening ability. i guess it makes sense that you wouldnt want your main pulley to change speed even faster than it already does, wearing out belts faster.

[NORCAL300ZX916]

time for an upgraded under drive pulley

Should i get one or just find stock pulley. What is the advantage of an underdrive pulley?

although i have come across statistics stating losing 1lb of weight off the crank gains 2.4 hp

[DanDrath]

its supposively a 16-18 hp gain on n.a probably cheaper than a stock pulley i didnt look it up but i would imagine it is. I have one my buddy has one with no problems i havent really heard of anybody having problems with them. Only think i can think of is if u have a big mombo jombo stereo your light might start dimming when you are idling do to the alternator not turning as fast.

[bentandbuzzin]

i was going to my local z specialist and he cautioned me against the underdrive pulley due to its lighter weight it lacks dampening ability. i guess it makes sense that you wouldnt want your main pulley to change speed even faster than it already does, wearing out belts faster.

I heard the same thing about the lighter pulleys. I heard that the lighter weight can throw the crank off balance and possibly destroy the engine.

[evildky]

the stock crank pulley, aka harmonic ballancer has a membrane sepperating a weighted ring form the inner ring, this absorbs the natural harmonic of the engine and helps ensure a smooth idle and a long life

many ballanced race engines do nto run a ballancer and some cars do nto sue them, most honda's for instance

the power gained by an underdrive pulley comes in 2 ways, first reducing the rotating mass, this is actually a very small gain, low single digits, not enough to actually notice, second this smaller diamter slows down the accessories being driven, meaning your alternator water pump, power steering pump, and even a/c are spinning at a slower rate, this means they are not working as efficiently so that you can reduce the drag by another very small amount also not enough to feel, and the acessories are running at less than optimal speed but still within a reasonable range taht you won't miss the loss of cooling charging etc

if you watn a stock replacement I can sell you 1, $20 shipped in the US

[bentandbuzzin]

the stock crank pulley, aka harmonic ballancer has a membrane sepperating a weighted ring form the inner ring, this absorbs the natural harmonic of the engine and helps ensure a smooth idle and a long life

many ballanced race engines do nto run a ballancer and some cars do nto sue them, most honda's for instance

the power gained by an underdrive pulley comes in 2 ways, first reducing the rotating mass, this is actually a very small gain, low single digits, not enough to actually notice, second this smaller diamter slows down the accessories being driven, meaning your alternator water pump, power steering pump, and even a/c are spinning at a slower rate, this means they are not working as efficiently so that you can reduce the drag by another very small amount also not enough to feel, and the acessories are running at less than optimal speed but still within a reasonable range taht you won't miss the loss of cooling charging etc

if you watn a stock replacement I can sell you 1, $20 shipped in the US

You're just full of info. from now on your new name is professor evildky.

[NORCAL300ZX916]

many ballanced race engines do nto run a ballancer and some cars do nto sue them, most honda's for instance

hondas do use a balancer shaft to correct only having half a motor!

[bentandbuzzin]

Can i use a balancer from a j30? It looks a bit bigger. I guess i can get the belt as well.

[AZDave]

Do you still have that stock harmonic balancer for an 1987 300 ZX? If so, I would like to purchase it. - Dave [email protected] 480 201 6201

[t.mcginley.jr]

AZDave, have you checked in the 300zx classifieds section? Someone there might have one they can sell you

[J30tChumpCar]

[/quote]
although i have come across statistics stating losing 1lb of weight off the crank gains 2.4 hp[/quote]

i was going to my local z specialist and he cautioned me against the underdrive pulley due to its lighter weight it lacks dampening ability. i guess it makes sense that you wouldnt want your main pulley to change speed even faster than it already does, wearing out belts faster.

Try asking someone thats running one if they are having problems, never heard of it causing issue even on moderate track cars.. oh a aluminum under-drive pulley saves not 1 or even 5 pounds it is 10+lbs lighter then stock!

The only downside is you will need all new belts and the alternator belt will need cranked tighter then normal to prevent slip and sequel