• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

4.0 Pulleys-Looked Everywhere I Cannot find...

D

digibts

Guest
4.0 Pdhleys-Looked Everywhere`K Cannot find...

Getting a little frustrated, I have looked all over for some undtv drive pulleys`gor my (8 4.0, l do any`kf xou jdow where I can get some or possibly a set from a different vehicle that will work well.
Or possibly even a c~ipany txkt villpmachinepqome for me.
 
There aren't any underdrive pulleys available for the 4.0. You could try ASP or March and ask them if there are pullies from other models that'll interchange.
 
A friend fabricated one, Aluminum, at a machine shop. It's smaller than the stock one for 4.0L.

I was afraid it will alter balance or create vibration.

Is the 4.0L pulley neutral or does it have any mass balance attached to it.
 
Last edited:
Faiz, the 4.0 is internally balanced so you don't have to worry too much about the weight/size of the harmonic balancer. Just make sure it isn't too light otherwise it won't adequately dampen the crankshaft harmonics and the engine will feel rougher at high rpm.
 
Woudlnt smaller pullys alter all the acc.?? With a smaller pulley it will have to rotate more to get the same effect correct. So the alternator wont be charging as well at idel and such??
 
That's the point of an underdrive pulley. You put them on the accesories that you don't neccesarly need to spin full tilt--the factory builds in some tolerance for extreme climates and inefficiant systems. That is, however, the main reason they don't make them for the 4.0 . Most of the 4.0L performance stuff is geared toward offroading and towing stuff, not speed. High RPM & slow speed (trail) or towing are deffinetly two situations you do not want underdrive pulleys.
 
I already asked around at March and ASP, and they weren't much help. Looks like we're on our own...

Having said that, the power steering pump is a metric Saginaw case, so that should be fairly common (Camaro/Firebird comes to mind) and the RENIX alternator is a Delco, so we're back to the Camaro/Firebird app as well. The water pump pully would probably have to be made (but I'd not want to mess with that one, with the design temp of the 242 being about 210-215) and reducing the AC is a pain because you have to fit the clutch in there.

Reducing the upper idler would have no net effect on power at the wheels, but reducing the lower idler (the one with the fan) would decrease drag somewhat - again, with reduced cooling.

Don't forget that if you go with smaller pullys, you'll have to go with a shorter belt as well.

And, if you THINK you're going to spend any time off-road, I concur with other opinions - underdrive pullys are a bad idea. If you're "street only," then go ahead.

Underdrive pullys will reduce accessory output at low RPM - alternator output at idle will be lower, and it will be a little more difficult to steer at or near idle due to reduced system pressure and volume output. That's why underdrive pullys are typically found on street only or racing cars (that live at high RPM) and not on trucks or off-roaders.

5-90
 
Back
Top