love-my-V8-280Z Posted December 28, 2003 Share Posted December 28, 2003 Ok, I need a crank underdrive pulley for my LT1 to not rub on the cross member. What is a underdrive pulley? Just a smaller pulley? And as for a Water Temp sending unit, Lets say I tossed my 280Z motor not think I may need parts of it... Can I just buy the Stewart-Warner sending unit, use it to replace the unit that came on the LT1. Assuming it has one, it does right? Ok, every time I ask a question, the answer generates two more! Overwhelmed and liking it! Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 28, 2003 Share Posted December 28, 2003 What is a underdrive pulley? Just a smaller pulley? This answer shouldn't create two more questions. Yes, an underdrive system can be as simple as a smaller crank pulley only, or more complicated by using larger pulleys on each of the ancillary devices as well. I've used one on my 240SX and love it. I not only noticed a very slight performance increase, but I have rationalized it's purchase based on less wear-and-tear on the ancillary devices due to their slower spin rates on my frequent 6k driving style. Quote Link to comment Share on other sites More sharing options...
love-my-V8-280Z Posted December 28, 2003 Author Share Posted December 28, 2003 Well sure enough now I have 2 more questions One I can figure out after I go get my dictionary... The other is what size should I buy? My concern is it hitting the crossmember, I like the idea of a two row pulley I would think I would be able to somehow figure out how to use the second channel to run a A/C. Can I just walk into my local Nappa and order one? Thanks! Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 28, 2003 Share Posted December 28, 2003 I'm not well versed in this area, but here are my thoughts. I'd stick with something no smaller that about 20% (keep the % of underdrive at or below 20 such as 18% for example) underdrive for a daily driver. I say this because the A/C, alternator, and water pump, even though they turn slower now, will still be able to provide their services at idle or slightly above. When you slow them down even more, you will start seeing the effects. When I raced my car, I was using a 50% underdrive, and this worked fine with only a water pump on it, but now that I am street driving it (plus I have a power steering pump on it) and I needed more speed at these devices. I don't know if NAPA sells these or not. I bought mine directly from Unorthodox racing, but I think Ebay has them all the time for the GM motors. Whatever you do, do your best to find out what size belt(s) will be needed for your new pulley. I can be a PITA trying to figure this out on your own. Quote Link to comment Share on other sites More sharing options...
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