under-drive pulleys
 

Considering installing under drive pulleys . Any info pro or con appreciated.

Any reason why?

A little bit more HP due to less weight of the pulleys (aluminum) and a slower rotation on them, which is where most of the HP is found..

I run the March Pully setup... no problems,,,

Explain what you mean by "under drive"? Do you want your pulleys to turn faster or slower?

You might look into serpentine, worked out great for me.

although the serpentine belt looks (IMHO) mush better, and it is easier to R&R.... There is no HP gain or loss as compared to the standard multi belt design.

The under-drive pulley being larger at the crank, and smaller at the other locations, ie power steering, so the engine work less, thus having more top end HP

Thanks Paul but I wanted to be sure (as was 'bashcraft') what 'caryb78' was after.

I have an ultralight underdrive set up, pulleys have to be sized right. I dont think youll notice 1 bit of gain its more of a "want every little bit real or imagined"..Pulleys gotta be sized right.
Theres cheaper stuff on speedway, turn one KRC?? Wanted bearings that wont pop at high rpm;idles around 1200 rpm so charging isnt a worry
Waste of $ probably oh well lol

Kinda wanted AC but was afriad of belt issues or spitting a compressor out.

Have an RCR system (discontinued)which is pretty much the same thing as
http://www.jonesracingproducts.com/

From ls1 tech:Originally Posted by DamianYou gain more area under curve rather than peak HP with a pulley.

I've seen a solid 1-2 tenths/1-2 mph from a pulley swap. I actually swapped one @ the track once https://ls1tech.com/forums/images/sm...ch/gr_wink.gifYes that is what my dyno comparison showed as well. I think torque & hp were up well over 10 up to peak and 7-8 at peak.

I have a CVF Racing underdrive crank pulley. It was the only way I could stop the car throwing the power steering belts at high revs and steering effort on the track.

Convert to electric power steering pump.

This is backwards.

I'm aware of the so called advantages of under drive pulleys claimed by the manufacturers, but was more interested in the OP's reason for wanting them.

Sure,I guess that would've been an alternative! The underdrive did the trick though. Have you done it (electric power steering pump)?

x2 sorry bout tthe big pic

https://cimg4.ibsrv.net/gimg/www.cor...6365443464.jpg

Correct:-)
Smaller at the crank***

I went with an underdrive pulley on my LS years ago, could not tell any difference in performance from a "seat" perspective. In defense of the pulley, didn't notice any of my accessories performing any worse. I wouldn't waste you time or effort unless you were building a track car with an engine from scratch and plan to squeeze everything out of it you can.

Stock style alternators already have a hard time at low RPM, my fear would be the alternator.
My steeroids rack also doesn't like my stock power steering pump at low RPMs and I'd hate to make it worse.

There were some great dyno tests of underdrive pulleys and different accessories from HotRod or SuperChevy a while back and engine-driven fans were obviously the worst power loss, but after that was the water pump, if I remember correctly. The test compared a stock water pump vs a high flow water pump vs. an electric pump. -Then they installed overdrive pulleys and the most shocking thing was that an underdrive high flow water pump was almost dead-even on power vs. an electric water pump (because of the extra load on the alternator) AND the high flow water pump spinning at the reduced rate still flowed as much and cooled as much as the stock water pump with standard pulleys.

If I'm going to do anything it would be a bigger pulley on the water pump to slow just it down by 20% (already got the high flow pump).

I know the engine masters guys did something on this, but I haven't seen that episode on the FREE motor trend on demand yet..


Adam

Odd...... I also run a steeroids R&P, as well as a hydroboost....
And I am running the March under drive pulley system as well... My Water-pump is the Edelebrock Aluminum
And I do not have any problem with ether, wether at low or high RPM.... they perform perfect.
Note: the alternator I run is a power master 140amp.... charge starts at about 750 RPM,

pulleys
 

Nailed it. Thanks

looking for power