Upping the boost on my 8-71 blown big block

Old 11-04-2013, 02:21 PM
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f35rocket
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Default Upping the boost on my 8-71 blown big block

Here's the set up. 468 BBC. 8-71 with 2 750's. Jetted square with 72's. 8 to 1 pistons. 61 top pulley, 54 bottom, for about 9% under-driven. Runs on 93 octane pump gas. Chassis dyno'd at 461 hp, 420 ftlb tq. I'd like to kick up the boost, without having to go to race gas. I figure swapping the pulleys would be way too much, even jetting up the carbs. So, what size top pulley can I go to? And how much higher on the jets?
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Old 11-05-2013, 06:42 AM
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oldandtired
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Something is big time wrong, those dyno numbers are too low.
JMO
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Old 11-05-2013, 07:04 AM
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f35rocket
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Default Upping the boost on my 8-71

I thought so too. It was on a portable chassis dyno at a car show, so who knows how accurate?
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Old 11-05-2013, 02:37 PM
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zipper06
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Do you have a boost gage? Is the blower teflon stripped?

You can probably get away with 1 to 1 ratio with 93 octane but i wouldn't think any more than that.

JMO

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Old 11-05-2013, 04:10 PM
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f35rocket
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Thanks for the response!
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Old 11-18-2013, 06:47 AM
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f35rocket
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Default Upping the boost on my 8-71 blown big block

Is there any "rule of thumb" as far as jetting increase, when changing pulleys from 54-61 (9% under) to 54-54 (1 to 1)? Like, maybe, one jet size per two teeth or something? Just some sort of starting point, so I don't melt pistons trying to find the right combo!
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Old 11-30-2013, 07:56 AM
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roadkill2
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Default Re: Upping the boost on my 8-71 blown big block

Originally Posted by f35rocket
Is there any "rule of thumb" as far as jetting increase, when changing pulleys from 54-61 (9% under) to 54-54 (1 to 1)? Like, maybe, one jet size per two teeth or something? Just some sort of starting point, so I don't melt pistons trying to find the right combo!
Never heard of a "Formula" like that . . It's just "More air . . More Fuel".

Start with jetting that should put you rich and then lean it out to taste . . Kinda like making Chile . . .
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