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Boat 502
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Discussion Starter #1
Hey, just trying to learn a little bit about these "huffer" motors you guys run !:D So my first question is if somebody is running a 468ci w/ a 671 blower 21% over what the hell does that mean as far as compression/power. Is this another term for "boost" ??? Is this thing hauling the mail or is this mild ? Edjimacate me:)sphss
 

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Hey, just trying to learn a little bit about these "huffer" motors you guys run !:D So my first question is if somebody is running a 468ci w/ a 671 blower 21% over what the hell does that mean as far as compression/power. Is this another term for "boost" ??? Is this thing hauling the mail or is this mild ? Edjimacate me:)sphss

First off, a 468 with a 6-71 is kid sh!t, J/K. Boost is the amount of air forced in when vaccume no longer exists. 21% would be the % over 1to1.
 

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Boat 502
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1,298 Posts
Discussion Starter #3
First off, a 468 with a 6-71 is kid sh!t, J/K. Boost is the amount of air forced in when vaccume no longer exists. 21% would be the % over 1to1.
Ok so when you turn up the boost that is going to make that ratio (21%) increase ? Also, adding more boost to a motor is just a pulley swap, right ?
 

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Boat 502
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Discussion Starter #5
Last questions on this subject.....is there some kind of formula/breakdown to figure how much boost a motor is running if its 21% w/ a 671 ? Also what do you think a little 468ci w/ this set up is making hp wise ????
 

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Cantard
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5,017 Posts
Last questions on this subject.....is there some kind of formula/breakdown to figure how much boost a motor is running if its 21% w/ a 671 ? Also what do you think a little 468ci w/ this set up is making hp wise ????
Would need info like what heads you are using.
 

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Last questions on this subject.....is there some kind of formula/breakdown to figure how much boost a motor is running if its 21% w/ a 671 ? Also what do you think a little 468ci w/ this set up is making hp wise ????

I think BDS has a chart on their site with the #'s your looking for.


Darrell.
 

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mo balls than $cents$
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11,734 Posts
surprised noone has mentioned how hot the intake charge would be at 21% on a unintercooled 6-71. i ran a weiand 6-71 on my 475bbc last summer and there was no noticeable difference between 12% and 21%imo. i was taking out so much timing to keep from detonating the hot intake charge, that imo , it wasn't worth over driving that much unless i had a badass chiller. you start needing to run 21%, than its time for a 8-71:)bulb
 

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Boat 502
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1,298 Posts
Discussion Starter #11
I haven't even seen the motor I'm referring to yet. I'm going off what the guy said. I'm so used to talking about n/a motors that I was a little lost w/ the terminology. I motor has a intercooler on it though.
 

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Cantard
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5,017 Posts
surprised noone has mentioned how hot the intake charge would be at 21% on a unintercooled 6-71. i ran a weiand 6-71 on my 475bbc last summer and there was no noticeable difference between 12% and 21%imo. i was taking out so much timing to keep from detonating the hot intake charge, that imo , it wasn't worth over driving that much unless i had a badass chiller. you start needing to run 21%, than its time for a 8-71:)bulb
x2
 

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Hey, just trying to learn a little bit about these "huffer" motors you guys run !:D So my first question is if somebody is running a 468ci w/ a 671 blower 21% over what the hell does that mean as far as compression/power. Is this another term for "boost" ??? Is this thing hauling the mail or is this mild ? Edjimacate me:)sphss
I run an aftermarket blower in between a 671 and 871, set up by Littlefield, I run 7.5 pistons, merlin heads 15 % over, 12 lbs. boost WOT 6200 rpm w 32 gears in a 19 Sanger bubble..............runs pump 93 octane w/ 35 degree total timing............... about 60 hrs on motor............ runs mid 90's and punishes "100" MPH boats all day long................ All I gotta say is "It works for me"...................
 

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Cantard
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I run an aftermarket blower in between a 671 and 871, set up by Littlefield, I run 7.5 pistons, merlin heads 15 % over, 12 lbs. boost WOT 6200 rpm w 32 gears in a 19 Sanger bubble..............runs pump 93 octane w/ 35 degree total timing............... about 60 hrs on motor............ runs mid 90's and punishes "100" MPH boats all day long................ All I gotta say is "It works for me"...................
Are you pulling timing as you add boost or do you have it locked in?
 

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Are you pulling timing as you add boost or do you have it locked in?
MSD centrifugal, full advanced set at 3000 rpm, 8 degrees at idle......... seems so work good ............The curve is adjustable in the distributer. Thinking about buying a 21 v bottom v drive Rayson or Schriada or something of that nature .............. The flat beats an ol' guy up these days, and my wife still hates em'
 

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"It's HONDO, honey"
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Hydro, SSI 14-71, 38% overdrive. lots of boost to say the least. Go with an 8 you don't have to overdrive it as much as the 6 and it offers more if you want to up the ratio:D
 
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