I was looking through my handy-dandy JEGS catolog, under the tpi, ls1, and lt1 section. When I came across these under drive pulleys. Now my question or questions is, how do they work, how do they free up 10-15 hp, and do they really work. Are they worth the $143.99 price tag listed. Do they work better on a 350 as opposed to a 305?

90 firebird formula w/305 tpi.

 

Here's the deal on pulley's, basically you replace your crankshaft and alternator and sometimes waterpump pulley. the "underdrive" pulley's are smaller and lighter than the stock ones, the smaller pulley means that the engine doesn't have to work as hard to turn all of these accesories...thus freeing up some horsepower. I have the three pulley set in my car and I noticed at idle my volts are down depending on what I'm using radio, A/C and stuff like that. I was told that they will give an L98 up to 12.5 more horses at the wheels.

Hopes this helps you out a little.

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1992 25th anniversary edition Z28 (Black W/Red stripes) 5.7 L98 engine, 3.73 gears,
Aluminum under drive pulley's, Gutted air box, K&N air filters, Air Foil, Bosch platinum spark plugs,
8MM spiral core wires, stage 2 chip, engine oil cooler, soon to have a high flow cat with a 3" flowmaster exhaust and P7000 Perelli Z rated tires all around.
Did I mention the interior is fully loaded!

 

i have a set of Hypertech's (2 pully set-crankshaft, alternator) and also have a voltage drop at idle. increased the idle slightly 650-700 at idle and 1000-1100 in park. helps keep the juice flowing to 13 volts. really need the volts to have good throttle response off the line.

 

get a 2 piece set, the water pump pulley is a waste.. if you are worried about charging get the march power and amp set.. i wouldnt pay 150$ for them,, i got mine off of ebay for 55$.