[updated:LAST EDITED ON 29-Nov-02 AT 02:14 AM (EST)]Are there under drive pullies for the big six?

 

[updated:LAST EDITED ON 29-Nov-02 AT 10:57 AM (EST)]Here's my standard response to underdrive pulleys, FWIW:




In my somewhat informed opinion, this installation is counterproductive labor. Consider:

1. The alternator is controlled by the voltage regulator, which will cause the alt. to draw as much power as it needs from the engine, regardless of the speed at which it is rotating. This means that, with a smaller pulley, the belt will be put under higher tension (because of the shorter lever of the small pulley) and will be forced around a smaller radius curve. Both of these situations will cause the belt life to be significantly shorter, and the tension is applied directly to the alt. & crankshaft bearings, shortening their lives.

2. The power steering pump pumps fluid as demanded by the steering box. Assuming you will still want as much assistance in steering as with the larger pulley, at low engine speed you will cause the same problems as with the alt.: higher tension, smaller radius, shorter belt and pump lives.

3. The air pump is unregulated (and a VERY small drain on engine power), but underdriving it will still have some effects, to wit: at low engine speed, there may not be enough air flow available to the air injection system and catalytic converters to meet the goals the EEC was programmed for, resulting in high emissions/failed smog test/"Tread Heavily".

4. The difference in pulley sizes will change the total length of the belt(s), meaning you will not be able to walk into a parts or tune-up store and get the right belt(s) the first try. And when you get the new belt, it won't be the same one 5,000,000 other trucks are using, so it will cost more.

5. The only system that will probably be affected the way you intend is the A/C compressor, which will not be able to produce the pressure needed for the cooling system at low engine speed, which is when I assume you really want the power to be scavenged for propulsion. But you will STILL see the effects of tension and belt flex and WHY WASTE THE EFFORT??? Just turn the A/C off when you don't want the power to be drained.

I've spoken to engineers and other mechanics, and the opinion I've formed is that the underdrive pulley is a HOAX! I have never seen empirical evidence that the effect is appreciable on the trail, where you are paying for it to be. I think that anecdotal evidence ("I put them on and my rig works 1000% better now!"), while useful for some mods (like shocks, electric fans, tires, gears, etc.), is at best, questionable.

 

thanks for the info heres some more info about my truck i live in montana we dont do smog here and i was going to try to find a serpentine belt sys. i want to ditch emissions completly i heard that under drives (free up) horse power. im trying to decide if its worth it or not?



ok wheres the keys

 

also to go with my prev. post what about oil pan windage trays ive heard these free up horse power does any one make these for the big 6?


ok wheres the keys

 

You're wasting your time. All of that is voodoo physics. On an 8000RPM V8 dragster, underdrives & windage trays are necessities. On a daily driver, they're totally useless, especially on a straight 6 that never needs to go over 3500RPM. Get a K&N and a tuned exhaust and do the regular maintenance. It'll last forever and never give you problems. Start swapping crap around and trying to out-think the factory engineers and you're asking for trouble. If the smog system is working properly (something that's not as hard as many people make it out to be), it won't hurt performance.

 

ok ok i hear you screaming so no under drives and windage trays for a stocker but i like the idea of a serpentine belt sys. can some one help me here?


ok wheres the keys

 

You'll have to change all the bracketry for the engine accessories to get them all in line for a single belt, which means you'll also have to change the accessories to fit the new brackets and so you can get serpentine pulleys that fit. Look in your local junkyards for an '87-96 4.9L that they'll sell the brackets off of. Plan on recharging your A/C, too...

Although maintenance is a little more hassle, V-belts aren't that much worse than a serpentine. I made the switch when I went EFI, but I don't think I'd have done it just to do it.
http://www.webphotos.com/list_photos.asp?mi=3&smi=2&a=13217

 

[updated:LAST EDITED ON 29-Nov-02 AT 01:32 PM (EST)]maint. and looks is what im looking for i dont have ac will this effect the parts you told me to find?


ok wheres the keys

 

Well, you'll just have to find the brackets for the A/C delete option and buy the shorter belt. They might have just added an idler pulley in place of the compressor, which would make your life a LOT easier, but if you have trouble, just buy a junk compressor with a good pulley & use it as an idler. That might be the cheaper way to go, anyway, considering the prices of the belts - the A/C belt (being more common) MIGHT be cheaper than the A/C-delete belt.

 

You'll also need to change the water pump. The serp. belt drives it the wrong way.

 

[updated:LAST EDITED ON 30-Nov-02 AT 00:45 AM (EST)]Ooooh! Good call! I forgot that! Fan clutch & fan, too.

 

[updated:LAST EDITED ON 30-Nov-02 AT 01:03 AM (EST)]that is a big help i didnt know about that thanks you just saved me a lot of money can i use a electric fan and ditch the old set up???






ok wheres the keys :P

 

Sure, but it's a LOT more expensive... And from my experience, it can't be any more reliable. I'm using a junkyard fan and a LLT replacement clutch and I've never had any problems. I've put about 150Kmi on the clutch, so I'm about to swap it for a new one, but it'll be free. You won't have that luxury with an electric fan.

 

well i want reliability this truck got to last so i geuss ill stick with a belt driven fan. now about this reverse style water pump will the 87-96 style fit on my 84?



ok wheres the keys

 

Yes. The block is the same, so either pump will bolt up & work. There's a slight chance you'd have to find a different lower radiator hose, but I think your original should work.