Author Topic: 8v-71 Blower drive ratio  (Read 2918 times)

Offline 3408cat

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8v-71 Blower drive ratio
« on: August 10, 2009, 02:41:30 PM »
I'm trying to come up with some low dollar horsepower gains - pistons, turbo, and coolers are not within my budget). What I was wondering that instead of the normal advance the timing, big injector black smoke thing, what about more air and more fuel. Are there different blower drive ratios for 8v-71 engines ? Most truck 8v-71 are 318 hp. Can I set up my engine to have the right torque curve for a 4 spd manual trans and have 318 hp by changing injectors and blower speed ?  Thanks, Bill.

Offline luvrbus

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Re: 8v-71 Blower drive ratio
« Reply #1 on: August 10, 2009, 05:33:23 PM »
3408, there 3 or 4 different ratios for the blower drive along with different blowers if you like I can look it up for you.FWIW the A timing doesn't help much on a bus with a 4 speed     good luck
Life is short drink the good wine first

Offline 3408cat

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Re: 8v-71 Blower drive ratio
« Reply #2 on: August 10, 2009, 05:57:22 PM »
Luvrbus, Is my thinking correct ??? I have access to free junkyard 8v-71 engines. If I knew how to tell which ones are which by serial number or engine code I'm sure I can find the parts I need to change mine. Would you know where I could find any of that info ?

Offline Don Fairchild

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Re: 8v-71 Blower drive ratio
« Reply #3 on: August 12, 2009, 02:50:22 PM »
Bill;

There are three gears that were used in most of the V engines, a 38 tooth a 39 tooth and a forty tooth gear. The 40 tooth slowed the blower down 5% from the 38. The only one that will speed up the blower is the step up gear found on some 6 & 8 V 92 naturals.

Don

Offline luvrbus

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Re: 8v-71 Blower drive ratio
« Reply #4 on: August 12, 2009, 05:29:03 PM »
3408, here are the drive ratios I found so far for a 8v71

205:1
200:1
195:1
175:1 used on industrial N/A engines for operation above 10,000 ft

I will keep digging through the books and see how much each ratio changes the air box pressure and what blower produces the most pressure and air.
   


good luck
Life is short drink the good wine first

Offline 3408cat

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Re: 8v-71 Blower drive ratio
« Reply #5 on: August 13, 2009, 03:11:25 PM »
Thanks guys for helping me with this one, Do you think I will gain as much as I'm thinking = 25 - 35 hp ???