Under Pulley?
03-11-2005, 12:13 AM
#11
1st Gear Member
Join Date: Dec 2004
Location:
Posts: 141
RE: Under Pulley?
Underdrive pulleys are definately worth it. I have a 1 piece March pulley. This one replaces just the crank pulley. Theoretically, and in actuallity they free up the engine by spinnning the belt slower. Think of it as the big pulley, little pulley scenarios from high school math. Its a lot easier for a little pulley to turn another pulley than for a big pulley to turn the other pulley. The smaller crankshaft pulley will remove some of the stress on the engine. In turn, the drive belt will turn slower. This is where you might have had your problem, Mike. I had the same problem when I made a custom pulley for my old dakota. The pulley was so small that the alternator didnt spin fast enough to create enough voltage at idle. This puts a heck of a lot of strain on alternator. If you run into this problem, you can buy a smaller alternator pulley. There is a ratio equation that you can use to figure out what size pulley you'd need for alternator, but I'd be easier if it just works the way it is, which it should. Hope this helps a little
03-11-2005, 12:28 AM
#13
5th Gear Member
Join Date: Mar 2004
Location: Northern New Jersey
Posts: 3,645
RE: Under Pulley?
I was thinking of getting them too. Will I have to get a different belt if I do that. My mind tells me yes, smaller pulleys = smaller belt. And what size belt would I need if I do need one?
03-11-2005, 01:17 AM
#14
1st Gear Member
Join Date: Dec 2004
Location:
Posts: 141
RE: Under Pulley?
I think I used about a 1 1/2" shorter belt, but it depends on the setup. If you buy a kit, it should tell you what size to buy. Otherwise, wrap a string around the pulleys. To figure out the belt size, do the following. Measure length of string, in inches(Make sure that tensioner is unsprung). Lets use 70", for example. Then, count number or ribs on old belt. Mine is 6 ribs. A common size would be a 700K6. This means a 70.0" belt, with 6 ribs. Bumper to bumper uses this. Another option would be a k060700. same basic principle, 6 ribs, with 70.0 inches. Otherwise, usually they will have a slide ruler made for figuring the length to size.
03-15-2005, 10:20 AM
#19
2nd Gear Member
Join Date: Jan 2005
Location: Cinci
Posts: 238
RE: Under Pulley?
Slowing your alternator down will cause more stress on it. Just think at night with headlights on defrost running on high and windshield wipers running while sitting idling at the light with your turn signal on.........and now you have your alternator turning slower than stock. I may be missing something but this couldn't be good. Also slowing your water pump down seems to explain itself.
Like I said I am all for easy bolt on power.....but I am just not sold on this yet. I would like to hear from peeps that are using new pullies
and how long they have had them and problems if any.
Anyone?
Like I said I am all for easy bolt on power.....but I am just not sold on this yet. I would like to hear from peeps that are using new pullies
and how long they have had them and problems if any.
Anyone?
03-15-2005, 11:17 AM
#20
5th Gear Member
Join Date: Feb 2004
Location:
Posts: 2,028
RE: Under Pulley?
I have run underdrives on my 04GT since it was new with no problems at all.The only thing you want to remember is to ONLY use non-piggyback pulleys.These have the harmonic balancer built into the pulley.The piggyback pulleys require you to bolt the old stock pulley to the new underdrive crank pulley so you will have a harmonic balancer.Without a harmonic balancer the crank is subjected to torsional vibrations that can cause the crank to break.Steeda and March sell non piggyback pulleys.Without looking,I think they cost around $150.The cheap ones are piggybacks.