C2 BB's, why the "captured" water pump belt?

[Steven S.]

Just wondered what the reasoning was for using the captured belt for the water pump? I assume the alternator belt alone was inadequate for one reason or another.

Thanks,
Steve

[Joe L.]

Re: C2 BB's, why the "captured" water pump belt?

Just wondered what the reasoning was for using the captured belt for the water pump? I assume the alternator belt alone was inadequate for one reason or another.

Thanks,
Steve

Steve-----


The only ones that know for sure are the GM engineers involved in the design of the system. However, it's not just C2 big blocks that used the captured belt. Many C2 and C3 small blocks used them as well as most C3 big blocks. C3 big blocks with C-60 used a water pump-to-crank belt but it wasn't, technically, a captured belt since there was an idler pulley in the system.

[Edward J.]

Re: C2 BB's, why the "captured" water pump belt?

Steve I'd Say That The Pump Speed May Be Slowed Down With The Length Of The Alt. Belt, The Captured Belt Is Almost Like Direct Drive From Crankshaft, This Means More Circulation From The Pump.also Can Act As A Safety If Alt. Belt Fails

[David T.]

Re: C2 BB's, why the "captured" water pump belt?

Steve I'd Say That The Pump Speed May Be Slowed Down With The Length Of The Alt. Belt, The Captured Belt Is Almost Like Direct Drive From Crankshaft, This Means More Circulation From The Pump.also Can Act As A Safety If Alt. Belt Fails

I don't see how the water pump speed would be changed. Shouldn't the water pump turn at the same speed with either or both belts in place? I do agree that it would act as a safety and also provide more torque to the pump.

[Michael H.]

Re: C2 BB's, why the "captured" water pump belt?

Just wondered what the reasoning was for using the captured belt for the water pump? I assume the alternator belt alone was inadequate for one reason or another.

Thanks,
Steve

The idler belt usually found on high performance engines assists the single water pump/alternator belt at high RPM.
Most often used on solid lifter engines but occasionally used on high perf engines too, such as the 350 HP 327.

A water pump requires a lot of energy to turn at high RPM and often causes a single belt to "loose it's way" to the next pulley in line.

[Clem Z.]

Re: C2 BB's, why the "captured" water pump belt?

unless you did mods to the alternator bracket with a added belt retainer you would throw off the long belt at high RPMs as it would "climb" off of the alternator pulley. you can drive a while with out a alternator turning but not too far without a water pump turning. we always use a corvair belt on the long belt because they were a better quality belt and would not stretch out and come off at high RPMs

[John H.]

Re: C2 BB's, why the "captured" water pump belt?

Steve I'd Say That The Pump Speed May Be Slowed Down With The Length Of The Alt. Belt

Component speed of rotation is unaffected by length of the drive belts; the only thing that affects speed of the water pump (or any other belt-driven accessory) is the relative diameters of the driving and driven pulleys.

[Mike M.]

Re: C2 BB's, why the "captured" water pump belt?

Simple, these were designed as race cars.
In addition to what has been mentioned previously,
let's say you are leading late in a race. Overheating is always a problem.
With a single belt design, a thrown belt with result in a fairly quick water pump melt-down with a potentially fatal engine outcome.
With the captured belt design, if the alternator belt gets thrown, there will probably be enough current supply from the battery and with the captured belt continuing to service the water pump offers a much better chance of finishing the race.
HaND