BBC pulley sizes - Chevelle Tech
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post #1 of 6 (permalink) Old Jun 10th, 07, 11:36 AM Thread Starter
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BBC pulley sizes

I was just checking my pulleys on my 454, and they are from Classic camaro. The crank is 6-1/2" and the waterpump is 6" should the crank be larger to drive the waterpump faster to increase flow and cooling?

My 468 has 12.3-1 compression, AFR heads and a big soild roller. It made 708 HP on the dyno, and 622 TQ. The distributor is locked at 38 degrees timing,so it has 38 inital as well. The cooling is as follows a griffen 2 row 31x19 rad, new 16 LB rad cap 180 Robert shaw stat.and a GM shrowd. the fan is a Plastic 17" flexalite fan.

On warm days the car will run 200-210 sitting in traffic once i get it rolling in clean air, it drops down to 190. I was wondering if i need to increase the crank pulley size if that would help? Or is this just the way its going to be with this type of engine on the street.

Sheldon

My other car. 1977 camaro prostreet car.
9.65 @ 137 MPH-1.39-60' more left in the car.


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post #2 of 6 (permalink) Old Jun 11th, 07, 2:09 PM
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Re: BBC pulley sizes

Are we talking about SWP or LWP here?

The LWP uses a creative set of pulleys on the BBC with two different diameters on both crank and water pump. When I measured the crank I came up with 6.75" and 7.75" diameters. On the water pump it came out to 5.5" and 6.25" diameters. Both of these result in a 1.25 overdrive between the crank and the water pump based on pulley circumference (which is what the belts see).

I don't think I would recommend increasing the drive ratio. If you rev to 6000 RPM, your fan/WP is going to be turning 7500 RPM. This is fine if they are designed for it but if not...

It sounds more like you need a better fan. The factory used the thermal fan clutch in there for a reason. They could use a big high pitch fan and gear it down through the fan clutch viscous coupling. This would make it easier to turn and also make it turn slower. Then when things got warm they could lock up the clutch and take advantage of the overdrive ratio built into the pulleys for extra air flow at slower/idle speeds.

Steve
1968 El Camino, 402 with TKO
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post #3 of 6 (permalink) Old Jun 11th, 07, 9:44 PM Thread Starter
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Re: BBC pulley sizes

I use a long waterpump and spin the motor to 6800 on the motor, and it will most likely see 7400 on nitrous going through the top end. well i guess i will just have to live with it?

My other car. 1977 camaro prostreet car.
9.65 @ 137 MPH-1.39-60' more left in the car.


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post #4 of 6 (permalink) Old Jun 12th, 07, 2:55 AM
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Re: BBC pulley sizes

Hmmm... that works out to 9250 RPM at the fan. I have seen some 8000 RPM fan ratings. So this is definitely something you need to watch out for.

I might consider converting over to electric fans in your case.

Steve
1968 El Camino, 402 with TKO
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post #5 of 6 (permalink) Old Apr 14th, 19, 5:49 PM
 
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Re: BBC pulley sizes

Quote:
Originally Posted by Grumpy 427 View Post
I was just checking my pulleys on my 454, and they are from Classic camaro. The crank is 6-1/2" and the waterpump is 6" should the crank be larger to drive the waterpump faster to increase flow and cooling?

My 468 has 12.3-1 compression, AFR heads and a big soild roller. It made 708 HP on the dyno, and 622 TQ. The distributor is locked at 38 degrees timing,so it has 38 inital as well. The cooling is as follows a griffen 2 row 31x19 rad, new 16 LB rad cap 180 Robert shaw stat.and a GM shrowd. the fan is a Plastic 17" flexalite fan.

On warm days the car will run 200-210 sitting in traffic once i get it rolling in clean air, it drops down to 190. I was wondering if i need to increase the crank pulley size if that would help? Or is this just the way its going to be with this type of engine on the street.

Sheldon
I have the same problem,today a race car mech. told me to use a larger then stock water pump pulley,he says you want the water to flow slower so it carries the heat out to the radiater.Iam looking now for a bigger dia. pulley for my 454.
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post #6 of 6 (permalink) Old Apr 15th, 19, 8:21 AM
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Bob
 
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Re: BBC pulley sizes

On my one owner LS-5/M-22- with A/C it has all the Org. engine pulleys. All the pulley numbers start with " AO " . If you need any pulley Diameters let me know. I also run the 811TX water pump.
P.S. Stock clutch fans & Blades, For the most part never spin over THREE grand.
ALL the big three Ford, Mopar, G.M. big cube High H.P. engines ALL had clutch fans. The MOPAR 426 Hemi GAINED 17 H.P. using a clutch fan. Overdriving the water pump may cause the coolant to be removed from the heat exchanger before it has dropped in temp. The correct fan blade, Moves XXXX number or Cu. Ft. per Min. not only pulls ambient air through the heat exchanger it also removes Super Heated Air from the engine bay.
Super Heated Air will cause problems such as VAPOR LOCK or boiled fuel, High engine Temps Etc,Etc.
Bob


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Last edited by Robinls5; Apr 15th, 19 at 8:39 AM.
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