Anybody got any dyno results for underdrive pulleys on an LT1? I know the water pump is probably the biggest drain, which isn't belt driven on the LT1 and I run electric anyway. I also know that on my 92 I'd have to convert over to the single sided belt, which requires a few new things but nothing major.

Just continuing to look for those few extra horses. Anybody have any exerience?

 

Nope, I have 'em. I just didn't do a before and after test. Even though one place that runs "Dyno Days" around here charges $40 for 2 runs. That adds up :p: . Yeah I did that conversion too. I don't know why GM wanted to put on a double-sided serpentine belt... :rolleyes:

It's probably worth at least a solid 5hp. One thing I did notice after I did pulleys is that engine would "wind up" a little bit faster.

 

At this point 5hp here and there is all I want. I've got 379 rwhp. I would love to see 400 out of a Hot Cam car. Revised exhaust and underdrive pulleys might give me 15. Where else! It shouldn't be that hard to get those extra horses.

 

They were good for about .05-.10 in the quarter on my car

 

What all do you have to switch out to change to a single-sided belt?

 

I think a Tornado would definitely give you some more power... and about 15 lbs of vinyl would help too. :lol:

Well I guess you could also look at fluids. Try out some of the high performance fluids from Amsoil or Redline in the rear end... transmission and engine. Reducing driveline friction would get more power to the ground... just not more engine HP (unless you change engine oil as well). Maybe 1 or 2 RWHP possibly more. That’s closer and closer to your goal.

 

I believe all I changed was the tensioner, power steering pump pulley, and one idler pulley. I could look up the P/N if you're interested. :cheers:

 

So, everything except the alternator pulley, or did you forget to mention that one? There has got to be a better way than changing all of the pulleys.

 

The idler pulley, tensioner, and PS pulley are all you have to change. The first two are extremely easy, the power steering I'm not so sure about. It sounds more complicated than it really is.

 

:iagree: Yeah, it’s not that hard just three things to change and you're done. You need PS pulley remover to get it off. Just go down to an AutoZone or similar store and you can "rent" the tool for a deposit. Once you return the tool your deposit is refunded... almost free except your gas. It's not like you use a PS pulley remover everyday. :cheers:

 

What brand pulley are you running? How's the alternator charge?

That's about my biggest concern right now, my alternator is a little weak at idle. It's been freshly rebuilt by a very good shop and it does a good job UNLESS I'm idling, with the A/C or defroster on, headlights, wipers, and stereo blasting.

I'm sure my MSD igntion and Electric water pump aren't helping either. I need to just shell out the money for a powermaster 200 amp. It puts out as much at idle as my current one does running full tilt!

 

Summit sales a pulley for the alternator that makes up for the difference. I had alternator problems at idle until I got that pulley from Summit. If I knew the part number I would post it..

 

I bought the 2 pulley system from ASP. I didn't like how low the voltage was with the larger alternator pulley... so I just have the crank pulley. That's the main gain there. It hangs around 13.0 with the alternator pulley. Headlights were dimming a bit... they would brighten once I took off. With the stock one it hangs around 14 give or take a few tenths depending on idle speed (cold vs. hot - readings were taken at the digital gauge). Other than that no problems. Except playing belt roulette to find the right one. Even the original belt ASP suggested was waayyy too tight and would not fit. Then I had to play with belts again since I put on the stock alt. pulley, but I found one that works perfect.

 

Nathan,

My car is a 94 LT1. I put the pulleys on when I changed my opti over to a DynaSpark. No Dyno numbers, and to be brutally honest, nothing that I can recall on the old Butt-ometer either.

I installed the March Underdrive pulley system. I did have a problem at idle with charge, and if you have a dailey driver, that should not be underestimated. If you sit in line at a burger joint, than park to eat your meal while you listen to the radio, it is possible that you may have to get a jump to drive off. (If that sounds like personal experience, well, it is..)

I could not believe the engine pulled down the battery that fast. All it has to do is get to below 11 volts and starting is definitely questionable. To quantify, sitting in idle for 15-20 minutes could be a problem.

March makes a pulley that restores alternator operation to optimum, that now comes with their system. I had the misfortune to have one of their earlier systems, but it only cost me twenty bucks to fix the problem. Long story short, every bit counts, so if you can reduce engine parasitic drag by a set of pullies, you are in the plus column for HP. The A.C. and power steering handle the reduced rpm just fine, but don't compromise operation of the alternator output. There are just too many real life situations, such as traffic, that will make you feel the impact of that oversight.

Best of luck to you in school.

:cheers:

 

Nathan,
I think with the underdrive pulley, you may see a 5-10rwhp gain...it'd certainly be good to see if you did. I'm watching your posts aswell, because I want to see if you can hit that 400rwhp mark too. :cheers:

 

I don't remember where but I read once where it was very little benefit on an LT1, maybe 3-4 HP. But if you're seeking those incremental gains, it'll add up.