Changing Lower Pulley

[mkorgan]

I looked before I asked but did not find exactly what I was looking for so I thought I would ask.

First of all, I want to thank everyone on this forum for making working on my ZL1 so much fun. Seeing what everyone is doing with their cars, what works and what doesn't, and how to best get things done is absolutely fantastic and I for one appreciate it since I do not have a group of guys I hang with (married w/ 4 kids and travel for work) so my "virtual Z family" is fantastic.

With that said, my next mod is the lower pulley/balancer. From everything I have read I believe there appears to be two size to pick from 8.6 and 9.1 so my first question is "what is everyone else running and why did you pick the one you picked?"

My second question is "how hard was it to install and did you go in from the top or drop the pan and go in from the bottom?" I would think the bottom would be easier to get to the pulley once the pan is dropped but I would like confirmation from someone who has done it.

Thanks again for you input. Much appreciated.

[Skylane765]

I am going with 5% and Torco. You can run 10% and Torco also. To install the new pulley and adapter you will need a puller for the LS motor and I used the ATI installer that will also pull the ATI damper. Just pull the fans out to get room, but they do not have to be removed. That's all you need to remove. No need to remove the pan.

[Stephen12ZL1]

here are the pulley install potential issues that people encounter. Removing the stock balancer bolt can be difficult as it is torqued to approx 230ft/lbs (37ft/lbs + 140 degrees). If your car is an automatic, the engine will turn and you have to use a tool to lock the engine at the flywheel once the starter is removed. Otherwise, you can use an air impact tool to remove this bolt (24mm). Next, the lower balancer must be removed using a puller like the OTC 6667. The A/C belt is a "stretch fit" and it will come off with the stock balancer. To reinstall: don't forget the seal on the snout of the balancer. Use a proper install tool like a hawk tool or equivalent threaded rod and nut/washer. You could use a longer M16 bolt but it is not advised as some have pulled the threads out of the crank this way. Make sure the keyway is aligned properly before install which is obvious. Torque the new GM bolt to 37ft/lbs + 140degrees or 235ft/lbs for an ARP(preferred) bolt. You must use a large torque wrench for this duty. Use Red Loctite if you want on the new bolt...there are opinions on this. Reinstall the a/c belt by rotating the crank bolt and pressing the belt with your fingers or use an install tool(no need IMO). Reinstall the accessory belt and the correct length supercharger belt for the ring diameter you chose. Make sure belt alignment is correct.
Access from the bottom is impossible...must do it from the top.

[Skylane765]

The bolt on the stock LS came right off with a 1/2 Milwaukee battery impact gun. It will torque over 200. It surprised me but it will remove it, just let it go for 10 to 20 sec and it will come right off.

Yes just use your fingers to install the rubber band type AC belt. That is about the hardest part of the job. I made sure I have all the right pullers and installer, so I can change back if need be.

[hognutz]

Originally Posted by mkorgan

I looked before I asked but did not find exactly what I was looking for so I thought I would ask.

First of all, I want to thank everyone on this forum for making working on my ZL1 so much fun. Seeing what everyone is doing with their cars, what works and what doesn't, and how to best get things done is absolutely fantastic and I for one appreciate it since I do not have a group of guys I hang with (married w/ 4 kids and travel for work) so my "virtual Z family" is fantastic.

With that said, my next mod is the lower pulley/balancer. From everything I have read I believe there appears to be two size to pick from 8.6 and 9.1 so my first question is "what is everyone else running and why did you pick the one you picked?"

My second question is "how hard was it to install and did you go in from the top or drop the pan and go in from the bottom?" I would think the bottom would be easier to get to the pulley once the pan is dropped but I would like confirmation from someone who has done it.

Thanks again for you input. Much appreciated.

I thought it was easy I did not pull the belly pan but did pull the fans. buy the arp torque to value bolt. just orderd a kit with the OEM torque to yield bolt and found it to be a PITA.

there is 8.4", 8.6", 9.1", 9.5" pulley

9.5psi, 10.5 psi, 11.5psi, 13psi

the 9.1 requries a different idler pully $50 I think and the 9.5 requires a whole relocation bracket like $200 I think.

I already had the rotofab CAI, 90mm tb I got as gifts so I went 8.6 to start with. I did not want to run out of injector but I may have been able to get away with the 9.1 but chose not to risk it.