derekguzz

another thread that has been posted many times.

I have a 94,6spd..hoping to have around 375-400 to the motor after I am done.

My last question I have is what EXACT underdrive pully set to go with.

I am looking for a complete set. I do not want to mix match.
I have no experience with pullys. I am wondering where good deals are and what kits do NOT have charging issues.

Can anyone point me in the right direction. and let me know where they bought their kits. How do I make sure I get the right length belt and the right kind? This is something I am new with !!!!

engle1147

I'm sure March Performance has a pulley kit for your year why not check with them: http://marchperf.com/

I believe most reported charging issues occur at low RPM (idle). I would think worst case scenario you could just increase (reprogram) your "target" idle RPM a bit.

cv67

Although not an LT1 used an underdrive kit on an sbc
Used a high output water pump to compensate cools fine.

Alt pulley leaves the battery slowly draining though need a smaller pulley.
Not sure how the ones made for the Vettes keep up, sure they are probably somewhat similar.

Jonnymac

ASP
http://www.aspracing.com/gm.htm#corvette

silverdroptop

I installed the March aluminum 3 piece underdrive pulley set on mine, No problems with cooling or charging.
Very nice pulley set but cannot comment on any performance difference because I installed the TPIS ZZ9 cam, TPIS BigMouth intake, AS&M semi-siamised runners and the pulley kit at the same time.

Calderone

AVL94LT1383

Quick question...
#1. LT1 = Cam driven water pump.... So what is the phatom under drive pully doing for the water pump?Are you planning on running A/C when you race? Even with AC on when you floor it the clutch disengages... so what do you gain while you idle and need to stay cool?
Depending what you are doing to get the 400 hp at the crank I dont think you will need to rev over 6000 so why risk the charge at idle.
Do you plan to be running 4k to 7k 90% of the time?
So if you are staying with the LT1 that came with the 94 and you drive on the street as I would assume at those hp targets save the money and spend it on hp producing parts vs hp savings snake oil.
See #1

engle1147

Parasitic accessory drag not a myth......under drive pulleys are not snake oil. Removing/reducing accessory load loss is the primary reason why people go with electric H20 pumps. The average accessory load on the LT1 eats ~ 10% of the available hp...even if you only stick an undersized pulley on the crank your still better off and have the potential to spin the engine up quicker. Sometimes it is easier to recover available hp rather than trying to produce additional amounts of it for the same net effect.

derekguzz

well being a 94 6spd. What pulleys should I be looking for. I don't want to deal with charging issues at idle. And how do I make sure I have the right belt length? Do I take a piece of string and trace the belt path?

STL94LT1

Then don't waste your money on underdrive pulleys for your LT1. The alt and power steering pump is the only units the pulley will affect. Get an electric water pump instead, this will eliminate he pumps drag.

Red Rocket

You shouldn't have charging issues if your idle is set at 900-1000 RPM's.
Buy a couple of Gates belts to get the right length. Plan on installing the ASP set up on my 396 and dyno next month.

AVL94LT1383

So 10% loss.... and how much will the underdrive save on the LT1? .. thats what I thought. If the underdrives cost 250 plus install: are you saying that is the best way to spend the $250+ labor?
Is that your best advice for the money ...? Really Now !!????
If you can purchase an electric water pump for $200 ... now how do you like the underdrives on an LT1.
We are talking LT1.... Right?

AVL94LT1383

Amen!

derekguzz

I am confused right now lol..

So there are no kits for my car? like click and see a couple pullys, send the money and bang im in?

Thats kinda what I am looking for. I am an un-educated guy on these pullies. I just want to buy them and install them. I should read a bit more about them huh?

87 vette 81 big girl

MARCH has been around for some time now.

You can take trust in thier products and Uderdrive pulley kits.

For a daily driver, or mild performance use, an electric water pump may be overkill. But can be used too if desired.

Electric water pumps are great for Big Horsepower production, like 600-1,400 HP on street driven drag race machinery.

Also electric water pumps are great for Half way filled MOROSO hardblocked or full hardblocked up engines running larges amounts of BOOST or Nitrous oxide.

Need very high volume of water flow at all times to keep such engines cool on the street or between rounds at the dragstrip.

engle1147

Wow -- you use more punctuation than I do....that is pretty hard to do.

Your kidding right - bottom line is if the accessory drive is using less of the engine output with an underdrive pulley setup installed - then more is available to the rear wheels.

A single crank pulley cost under $100 USD....3 bolts hold it to the balancer...remove the old belt & pulley install the new pulley and belt (if required).

I'm pretty sure I mentioned using the electric water pump early in the thread there buddy.

To the OP - I hope you're able to get the info your after - good luck with the rest of the overhaul.

turbotim23

The way I look at it with 10 to 15% better horse power and better gas mileage also, What have you got to lose! I would go with ASP they have a pulley that speeds up alt. for full charge at 900 rpm. You sometimes have to order and wait for them to make them. C4 corvette's aren't as big a market as they once were. Something nobody's said is that slowing down the power steering would be a good thing, as there are problems with the power steering hose breaking at high speeds.

STL94LT1

10-15% horsepower gain, 30-45 hp on a stock LT1.

You have money to lose.

So, on an LT1 you would only be slowing down the power steering pump with this mod.

Red Rocket

From March's website FWIW. A little long but informative.

Top 5 Questions About Underdrive Pulleys
1. "Do underdrive pulleys really deliver more horse power?"
Every experience we have with underdriving engine accessories shows that yes underdrive pulleys do deliver more horse power by freeing up power lost to parasitic drag. The amount you will realize depends on your car and the accessories you are driving, a car with alternator, water pump, power steering, A/C and a smog pump will see a larger HP gain then a car with alternator and water pump only. Dollar for dollar underdrive pulleys are one of the best value for HP gain on the market.

But don't take our word alone on this, every magazine we have seen who have tested under drive pulleys has show a HP gain, some as high as 12.5 HP. Click here to see how 5.0 Mustang & Super Ford "Bolted-on" an easy 15HP for less than $100! and all in under one hour.

2. "But won't underdrive pulleys cause a charging problem?"
Again that depends on your car and how and when you drive. Automotive manufacturers build a certain amount of extra capacity into their cars for situation of high demand like driving on a cold rainy night with the lights on plus whippers and defrosters going. An older car with a less then optimum charging system and a small weak battery may have charging problems with underdrive pulleys and some cars with monster audio installations require higher that normal electrical demands. A well maintained auto should have no problem at all. Sometimes raising the idle by 100 RPM is all it takes to bring the charging rate back up to normal.

If electrical charging is an issue with your particular application March Performance has a smaller alternator pulley available to increase alternator output but to still allow a HP gain from underdriving the other accessories.

3. "Won't underdrive pulleys cause a engine cooling problem?"
Again that depends on your car and how and when you drive. Putting underdrive pulleys on cars with already minimal cooling capacity could conceivably push the car into overheating but our experience is that 99.9% of the cars out there has enough reserve cooling capacity to use our pulleys. Some user find that the simple installation of a cooler thermostat is all it takes to bring the temperature back into normal range.

Underdive Pulleys can in some cases cure cooling problems. With racing applications cavitation can be a problem at high rpms. When a pump cavitates, it actually spins too fast to push coolant, Coolant must also stay in the radiator long enough to lose heat before returning to the motor so you can actually move coolant too fast. Both these issues can be solved by using underdrive pulleys.

But If low speed cruising is your thing then March Performance line of High Water Flow Ratios pulleys may be just what you need to prevent overheating in those situations.

4."Underdrive pulleys sound good but won't an electric water pump set-up give me even more HP?"
Yes it is conceivable an electric water pump can give you more HP than a underdrive pulleys set BUT there are some issues you should consider before you make that commitment. Your HP gain with an electric pump may not be as much as you think, in a recent test Hot Rod Magazine ran our performance ratios pulleys on a small block Chevy (alternator, water pump only) and to their surprise our pulleys only made 1 HP less then a electric water pump set-up. You should also consider that electric kits flow even less water then a underdrive pulley kit and that could cause cooling problems.

Most electric WP are made for racing applications and not designed to be run for long periods of time, and if that electric motor gives out you are stuck with no water flow at all unlike a standard water pump which may start to leak and make noise but can allow you to limp home.

The electric pump does draw power from your charging system and so you can't underdrive your alternator, you must have adequate electrical power just to drive the water pump.

5."How hard are they to install?"
Unlike engine modifications like cams, cylinder heads and intake and exhaust, underdrive pulleys can be the simplest power freeing modification you can do to your car. Some special tools are required such as an impact wrench to zip off the alternator pulley and a crankshaft dampener puller if your installation requires removal of the crank pulley/dampner assembly but all and all most kits are a simple "Bolted-on" operation. Our Mustang 5.0 pulleys can be installed without even draining the cooling system, Click here to see how to "Bolted-on" in less than an hour. Even if you are not the do it yourself type any automotive shop should be able to install your pulleys at a reasonable price.

tblt44