Tiha

can some one explain the advantages of this pulleys
http://www.ebay.de/itm/311914895784

Notice the stock crank pulleys is bigger in diameter than in this KIT - water pulley seems to be same...so what a smaller crank pulley do ?

olds 307 and 403

It cools much less and charges less as well. I had to upgrade to a 100 amp alternator and 403 never cooled right with that smaller pulley. They are good quality though. I used the top pulley and a larger March bottom aluminum pulley, still slightly smaller than stock. The idea is too under drive your accessories to gain hp. The factory used a pulley size similar to the March pulley I used, about 1.5" bigger than that one on the high prrformance models to not spin the accessories to fast at high rpm.

Tiha

are you sure that this kit cool less?..a friend use this kit on a 403 -030 over - mild cam with a champion alum rad. but with shroud and it cools really well

olds 307 and 403

Then he got luckier than me. I used the Champion 3 core and it was still a bit small. If he used the 4 core, sounds like it cools a good amount over the 3 core. Yes, it spins the water pump and alternator slower.

Tiha

....so are these pulley KIT are really worth...or more for shine and our eyes ?

It was 3 core he use in his 64...BUT THE SHROUD helps alot...do you use a shroud?

joe_padavano

Do you really think that some yahoo with a lathe will do a better job of picking pulley diameters (and resulting accessory speeds and cooling effectiveness) than the factory engineers who tested these cars under desert and arctic conditions?

Underdriven crank pulleys MIGHT be useful in very specific applications - such as a drag-race only car where you are only running the car for 15 seconds at a time. Try the same pulley combo in stop-and-go traffic on a 95 degree day and see what happens.

Rocketbrian

Speaking of underdrive etc. of pullies, the 70s A/C cars had a smaller water pump pulley, which according to the AMA specs in a kit that came with the GM Heritage package, the ratio of fan to crank was 1.40:1, while the non A/C cars had a ratio of .85:1, thereby turning the fan faster than the non A/C cars. Now, on 71/72 non-aired W30's without A/C I notice they came with a clutch fan, 5.5" pump and a regular pulley and no shroud. I don't know if they supplied the clutch fan set up for cooling at low speeds or more for power by eliminating the fixed fan. I went to this set up on my 71 442 that was modified a bit with higher compression pistons, as it cools fine while driving but creeps up temp while idling, indicating not enough cooling in that situation. Based on the ratios I mentioned, would I be on the right rack if I went to the smaller water pump pulley to turn the fan over at a greater speed while idling? I notice even when warm the clutch fan doesn't exhibit that roar you hear on A/C cars, giving me cause to think it isn't turning over fast enough to provide much benefit.
I realize this means going to three groove pulleys for pump and crank and a six inch pump to keep the belts aligned. Thoughts?

I apologize if this is hijacking the thread, but I thought it was relevant to the topic and I haven't seen this subject previously discussed.

olds 307 and 403

I know one guy who saw improved cooling with the 4 blade factory fixed fan over a 6 blade clutch fan. Yes you will see an improvement using the better ratio A/C pulleys. The 6" closed impellar pump will also make a slight difference and makes the swap possible.

Rocketbrian

Thanks.

rustyroger

Like Joe says, an underdrive pulley may have a place on a drag strip car, also I think on a car built for track use with a high revving engine.
But for street use, save your money for something useful.

Roger.