no1kicker Posted July 29, 2003 Report Share Posted July 29, 2003 I want a UD pulley and was wondering if you guys knew if most GM crank pulleys were the same size. I thought if some were smaller it would be possible to go to a junkyard and swap one and not have to spend the $100 for the new one. Just a thought. Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted July 29, 2003 Report Share Posted July 29, 2003 I think 2.8/3.1/3100 are the same size, Series I 3800 is bigger than those, and Series II 3800 is WAY bigger because the crank is not internally balanced. Another problem I would see is that with other GM crank pulleys (non FWD and non W-body), the belts maybe different widths, so the pulley from those wouldnt work. But, in all honestly I dont know, and actually have never thought of it, but its a good idea. Just make sure if you find a motor with one that will work, make sure the crank is internally balanced, like the 2.8/3.1/3100/3.4 Robby Quote Link to comment Share on other sites More sharing options...
Bowtiekid Posted July 29, 2003 Report Share Posted July 29, 2003 the crank pulley is the same size (same exact pulley) on the 2.8/3.1/3100/3400 (Approx. 6" dia). The 3.4 DOHC is also internally balanced, but it uses a different setup.... they have a seperate pulley that you can unbolt from the damper. Quote Link to comment Share on other sites More sharing options...
NeverSayDie Posted July 30, 2003 Report Share Posted July 30, 2003 sounds like you're thinking sdrawkcab dude. to underdrive your accessories you need a larger pulley, not a smaller one! just a tip Quote Link to comment Share on other sites More sharing options...
Bowtiekid Posted July 30, 2003 Report Share Posted July 30, 2003 Not if you are talking about the crank pulley. The driving pulley needs to be smaller if you want to under drive it. the driven pulley needs to be bigger if you want to do the same. Quote Link to comment Share on other sites More sharing options...
NeverSayDie Posted July 30, 2003 Report Share Posted July 30, 2003 thinking backwards i was, wiser than me you are Quote Link to comment Share on other sites More sharing options...
lukee1982 Posted July 30, 2003 Report Share Posted July 30, 2003 so if you were able to find bigger pullies for your alt powersteering water and air compressor or some would much horsepower be gained? Quote Link to comment Share on other sites More sharing options...
NeverSayDie Posted July 30, 2003 Report Share Posted July 30, 2003 you really don't gain any, it just frees up power you already had, but were losing to drag. probably 5 whp max Quote Link to comment Share on other sites More sharing options...
Bowtiekid Posted July 30, 2003 Report Share Posted July 30, 2003 you have to look at it as a percentage (or a ratio between EACH accessory and the crank)... if you wanted all your accessories to run 20% slower, then you would need pulleys that were 20% bigger on all your accessories. If you look at the water pump and p/s pump.... there isnt much room to go any bigger. (on the LQ1 at least). You also cant get larger a/c pulleys. You can get the same 20% under drive with ONE crank pulley since it drives all the other pulleys. You also save weight since its smaller VS adding mass to all the other pulleys. In the end, it is much simpler to use a smaller crank pulley. The results would be the same (if you ignore the fact that you add weight with larger pulleys), but one way is much simpler. Quote Link to comment Share on other sites More sharing options...
Bowtiekid Posted July 30, 2003 Report Share Posted July 30, 2003 as far as not gaining hp... no it doesnt make the engine more efficient at making power. It just uses it to turn the wheels instead of turning the accessories as fast. The FFP pulley actually shows a REAL (on a real chassis dyno) gain of over 10hp AT THE WHEELS at about 5000 rpm. Quote Link to comment Share on other sites More sharing options...
NeverSayDie Posted July 30, 2003 Report Share Posted July 30, 2003 ow! i was burned again! we have now established that i need more education on the matter of underdrive pulleys! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.