GM Truck 6.2 Diesel 82-88 25% Reduction Crank Pulley

[porboyz]

Saw this item advertised and decided to post it.

http://www.streetbeatcustoms.com/asp541200.html

GM Truck 6.2 Diesel 82-88 25% Reduction Crank Pulley (Full Charge 950rpm) (Nitride)

Under drive pulley systems increase engine horsepower by reducing the amount of power required to drive external accessories. For example, the alternator, power steering, water pump and air conditioner all rob horsepower from the engine. By replacing factory-sized crank and accessory drive pulleys with a resized pulley, the accessories are slowed, resulting in more horsepower available to drive the rear wheels. Fits GM Truck 6.2 Diesel 1982, 1983, 1984, 1985, 1986, 1987, 1988.

[john8662]

Hmm, interesting. I'd like to see a pic of the actual product, for the 6.2 because the one pictured is obviously for a smallblock.

Thanks for sharing, hadn't run across this one!

J

[Robyn]

I have seen these advertised before for many different rigs.

Here is my personal take on the idea.

The amount of power to run the accessories is not all that much and the the biggy is the fan when it comes on.

To slow everything down 25% in my opinion will cause issues with the AC's performance at low speed and could cause slugish operation of the power steering.

Now I will give it this, if you were running 4.10 gears in a rig that was seeing serious highway miles the reduction could be a plus.

Most Pickups and Burbs with 6.2's in the years mentioned had fairly high ratios though (3.42 ) Of course the HD 1tons and such would have lower gears.

Guess I just veiw a lot of this little stuff as goody yums to make the guy selling it some $$$$

Only way to know how it would perform would be to try one under a controlled set of conditions and see if it helps.

As John mentioned the piccy is from a mouse motor

Thanks for sharing

Robyn

[JohnC]

I'm gonna get me a high output water pump, lowe temp fan clutch and HO alternator, then I'm gonna drive them with an underdrive pulley. That way I won't need to worry about the freeze plugs with my single thermostat setup...

;)

[gophergunner]

seems to me that you would just be slowing things down for no reason....

first of all, if the alternator puts out a certain power at a certain rpm then lowering the rpm will make less power......you can't get more or the same power from your alternator by lowering its speed.

secondly....power steering, a/c, water pump? they are designed for ideal operations at certain rpms, so when your engine is idling these accessories will be slower, i don't know if it will work too well. when power steering slows down it usually isn't enough power to turn the wheels that easily(in some cases anyways)

this all relates to the point of trying to get the same amount or more power out of something by putting in less power. last i remember its not possible:confused:

[wfyehl]

Wouldn't that also affect the Tach reading by turning the alternator slower? You would have to figure out a way to re-calibrate the tach for the underdrive pulleys.

Bill

[DmaxMaverick]

Wouldn't that also affect the Tach reading by turning the alternator slower? You would have to figure out a way to re-calibrate the tach for the underdrive pulleys.

Bill
The model years of discussion didn't have a tach, or the tach was not driven by the alternator. Later models that had a tach were driven by the cam via the rear mounted vacuum pump, or an adapter (if no pump) at that location.

IMO, slower accessories are fine at the track, but have no business for street or daily driver use. The A/C, alternator, steering/brake booster and cooling is marginal at best at lower engine speeds as it is.