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Discussion Starter #1
Will twin Holley 750's deliver enough fuel for a 600 C.I. Big M,
Dart 320's,.660 lift roller,8-71 starting at 1:1 overdrive
in a 26Ft. DCB Cat? Got the boat used with this combo
but I sure would like a second or third opinion.
 

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not with the big m. sorry just kidding.

I would think you need min of two 950 or a pair of doms modded for blower app. and i feel your going to have to spin a 8-71 over quite a bit to fill 600 cubes. also i would check the rest of the full system can provide anough full to feed such a monster and keep your investment from burning a few pistons up.:)
 

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Discussion Starter #5
The Supercharger is fully striped and fresh.
I hope the weather holds out long enough to
finish the rigging and get a few runs in this year.
Boating in Ohio is short but SWEET.:)devil
 

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You could make alot of power with the blower and bigger carbs. 850 cfm holleys or more . Search the internet. I run dominators. Blowers love dominators.
 

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The 750's are good to about 6000 Rs at 1 to 1 on the blower. If you spin the motor or blower faster, your going to need more carb. The 8-71 on a 600 incher is good for about 5lbs boost at 1-1, if it is good shape. Maybe 6 if it is fully stripped.
You could make alot of power with the blower and bigger carbs. 850 cfm holleys or more . Search the internet. I run dominators. Blowers love dominators.
I don't think Lotsahorsepower misunderstood this. But some did.
It won't make one HP more with 950s or Dominators, unless he speeds up the blower or runs the engine passed 6000.

Maybe this is lost on some, but you aren't feeding a motor. Your feeding a blower. A 8-71 running 6000 Rs can't move 1500cfm. So what good is 2 Dominators.



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Blowers love the Big Carbs, Maybe it is more than a stamped cfm number on the box. But with my experience the more the better. Wanna Fight?:)devil
 

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The 750's are good to about 6000 Rs at 1 to 1 on the blower. If you spin the motor or blower faster, your going to need more carb. The 8-71 on a 600 incher is good for about 5lbs boost at 1-1, if it is good shape. Maybe 6 if it is fully stripped.
Blowers love the Big Carbs, Maybe it is more than a stamped cfm number on the box. But with my experience the more the better. Wanna Fight?:)devil
No. I don't care to fight. Your the one with the knowledge here. I want you to tell me how a 8-71 turning 6000 Rs can move more air thru a set of Dominators than it can thru a set of 750s. How many cfm does a 8-71 move in one revolution. Its fixed. It can only move so much per revolution, and no more. So how many CFM per revolution.



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No. I don't care to fight. Your the one with the knowledge here. I want you to tell me how a 8-71 turning 6000 Rs can move more air thru a set of Dominators than it can thru a set of 750s. How many cfm does a 8-71 move in one revolution. Its fixed. It can only move so much per revolution, and no more. So how many CFM per revolution.
I KNOW , I KNOW , :)hand
 

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Will twin Holley 750's deliver enough fuel for a 600 C.I. Big M,
Dart 320's,.660 lift roller,8-71 starting at 1:1 overdrive
in a 26Ft. DCB Cat? Got the boat used with this combo
but I sure would like a second or third opinion.
This formula gives you the cfm requirement
((cid x rpm)/3456) x ((boost/14.7)+1) = required cfm
example:
((600 x 6000)/3456) x ((6.5lbs/14.7)+1)
((3600000/3456) x ((.442177)+1)
(1041.667 x 1.442177) = 1502cfm


note: this is much easier when plugged into an excel spreadsheet.
 

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didn't want to run dominators when I built my blown 598 I talked to a few people
decided to run 1050 4150's quick fuel carbs gave them all the motor info had them
wet flowed seem to work real nice. no need for dominators
 

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Its not a matter of running Dominators or not. Its a matter of if the blower needs that much carb. Curious Hallett. What is it you don't like about Doms


As Carnivalride posted, its about 1500 cfm on 600 inch motor running a 8-71 turning 6000 RPM blower speed. My formula comes up with 1467, which is close enough. Havasubyou seems to think it needs 2100. Don't know why he thinks that. I'm certain he some pretty vast knowledge carbing a supercharger that has escaped BDS, RBS, and the Blower Shop.



:DCarnivalride: What I really want was the CFM per revolution of a 8-71.:)hand
Del51, feel free to jump in.



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:DCarnivalride: What I really want was the CFM per revolution of a 8-71.:)hand
I didn't look it up I was just going off boost, guessing about 6.5lbs at 1:1 with an 8-71 on 600cid but it was only a guess on my part.

That and showing him with a pair of 750's "theoretically" he only had enough carb for 6.5lbs of boost.
 

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It really isn't important to know how much air the blower moves per rev with a carb setup. You can just use boost charts and engine RPM to figure the carb size. But that explains the slight difference in our carb calculation. I was a little more conservative at about 6lbs of boost:D

I know Alky Express knows exactly how much a 8-71 moves per revolution. He has to, or he will be picking engine parts up off the bottom of his boat:D

You speed the blower drive up on a carb deal, and the carb just flows more fuel to meet the increase in air flow. With fuel injection, you have to adjust the fuel flow thru the system to match the air flow thru the blower, or BOOM.



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Is there some unwritten law saying a 750 only flows a maximum of 750 CFM? Holley flow rates their 4bbl carbs at 1.5" pressure drop. What happens if you increase that pressure drop to ...say 3" [Holley's rating for 2bbls] Is that same 750 carb still flowing 750 CFM? A carb doesn't care what it is sitting on, be it a blower or the engine's intake manifold as long as there is a pressure difference between the airhorn and the base plate there will be airflow, how much depends on whats creating that pressure drop.
 

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So what would motor run like that is over carbed? Poor throttle response? Poor fuel economy? Make more hp at less than full throttle?
Honest question
I worked for a guy years ago who ran a 350 w 6/71 @ 1:1 and 2 1050's....prepped by "Blown to the Bone'. And yes it was street driven...mini truck.....i would idle perfectly @ 1000 rpm pull to 7500
Never even had a fresh set of plugs in 2 years running every day.

And wouldn't having a carb that is to small cause a supercharger to work harder than necessary? It seems like a higher than necessary
vacuum signal on the inlet side would take more hp to turn than one with lower vacuum.
 

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Discussion Starter #19
Thank you everyone,
You have given me as many answers as questions.
All my experience has been with Blown Injected Alcohol
so I appreciate all the input.
 

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Will twin Holley 750's deliver enough fuel for a 600 C.I. Big M,
Dart 320's,.660 lift roller,8-71 starting at 1:1 overdrive
in a 26Ft. DCB Cat? Got the boat used with this combo
but I sure would like a second or third opinion.

ok so where in the orig post does it say anything about 6000 rpm max rpm?
 
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