I installed my under-drive pullies I think they are from March Performance. Black not polished (just more stuff to have to clean otherwise) they were pretty easy to install.

I used a 15/16th socket for the alternator, 9/16th for the 3 bolts on the crank pully and 5/8 for the set bolt on the crank pulley. I had to jerk around with belts cause they sent me the wrong size for my car -- sent me stock size 96 inch rather than 92.3 inch under-driven diameter. The belt code is 609230 which stands for 6 rib, 92.30 inches long. This is the kind of stuff that you find out all about when a simple mod fouls up on you.

Driveability: the car runs really well with the new pullies. I have to say I like it ALOT more than stock which tended to whine alot due to high accessory rpms I guess ? No big diff in alternator work (I have the HD unit for A/C). After about 2 minutes of idle the voltmeter on the dash guage starts to drop but I don't notice any difference in say the A/C fan or stereo. My fist impression was "hey the car sure runs good with these pullies... "

Performance: there is a marginal feeling in seat-of-the-pants test, mostly unnoticeable. Even so there have been some pretty big changes -- my effective redline has suddenly jumped to 5900rpm. No kidding I took a guy I work with for a spin just to show him (he has a '97 Z28). I will need to get roller rockers and new push rods before I spend anytime at 6k rpm in a 305. The car is definitely travelling faster at each redline so I expect my 1/4 times will have increased in mph ?

Conclusion: definitely a worthwhile mod for a 3rd gen car, certainly the 305 TPI. I really like the effect slowing down the accessories has on the system. I can hear more exhaust and less stuff whining up front. And the car defintely accelerates faster. Now if I can just figure out how to hook up that Jacobs system....

my .02 cents,
RP.

 

I've had starting problems since I installed the alternator pulley from my March Power & Amps set. Please let me know if you experience any problems with your pulleys.

 

I also have underdrive pulleys ( Mac) I have charging problems with these. In the city when im in traffic, the amp goes low, and gets worse when im in there for a long period of time. Especiallyt when i have the fans on. Maybe ill have to try the march pulleys. Tell me if you have any symnptoms of this.

 

Bugger wouldn't start again tonight It cranks fine, it just won't start. You boost it, it starts right away.

 

Usually, AcceldZ's GTA would require a bosst every 2 weeks or so since we installed his pulley's. Like the battery isn't getting sufficient charging it needs, but we had to boost it yesterday at a car show, and then again today at my place. Weird, the crappy Ac Delco battery don't help either, but that doesn't explain it

Dave

 

Update: I haven't had any problems sofar but of course it has been less than a weeks worth of use.

The car starts perfectly everytime. As a matter of fact it starts so quick (barely turns over) that passengers have commented on it. Probably has something to do with 8 new injectors, a tune up and the low kms (72k) ? It was like that before the pullies as well.

I have had pullies before on my '88 Formula that had the 70amp alternator and they were a problem on it. Mind you that was in Vancouver in November with the headlights, front and rear defoggers, windshield wipers and stereo on (rainy Vancouver during afternoon rush hour). This car has the HD alternator that may make a diff and I usuaLly only have the stereo on, nothing else. I have pulled the fuse on the DRLs -- doesn't the regulator fit into the picture somewhere ?

RP.

 

I popped in March underdrive pulley's a few weeks ago. Was a pain to get in.. crushed my pinky on a wrench slip.. ow... Black set, not power/amp series, 2 set.

So as far as charging goes, I tested it on Friday afternoon rush hour from downtown Toronto out to Brampton. Total time in traffic: 5 hrs. Avg temp 30 C with humidex like 40 C. I have no A/C lost charge long time ago and interior is black, man needed the fan on anyways. I drive with my lights on all the time and because its heavy traffic I have to run my rad fan on too. Interstate Megatron 650 Battery.

Results:

Avg Voltage 9-11 V
Avg Temp 190 F (I have a 180 thermostat)

Voltage dropped to 9 V on long stops with turn signals on. For the hell of it I turned on rear defroster and that got it down to 9 V quick. It always managed to stabilize though with no problem. I wasn't satisfied with such low voltage though but it was critical either.

I decided I'd paint my stock pulley black (alternator) and put it back on. It was smaller and lighter than the one from March, therefore requires more power to turn (remember bikes, small gear in back harder to accelerate) Basically its this the smaller the pulley, the more current you generate due to the ratio b/w the crankshaft and the alternator. Ratio you want is crank to go smaller, alternator to go smaller too. If it goes larger, you gain power, but lose current due to less rpm. I figured the difference in power was very small b/w the alternator pulleys but the voltage difference would be greater.

Results

Avg Voltage 12-13 V
Avg Temp Unchanged (Why would it change lol? Same coolant to crank ratio)

Under same conditions rpm for rpm, there is a considerable increase in V. I don't ever see it below 10 V and the power oomph you feel is there. It's almost as dramatic as going from 15x7 to 16x8 rims.

Idle is much better with stock alternator pulley than with the March alternator pulley with the stock one. Belt is not an issue, use the same one recommended by March it is a small change in tension, but well within tolerance. You still get the benefit of an aluminum crank that turns accesories less, thus freeing up torque and horsepower to the rear wheels. Some people can feel it, some can't. I'm an acceleration junkie I can tolerate up to 4 g's (been on north America's largest rollercoasters, made it a point to know how many g's they can create) without problem and am sensitive to it so can feel a slight push increase. The reality is, your torque does increase. (Simple physics) Therefore your acceleration will too.

My recommendation is get a set since every little bit you do will improve your car.