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Discussion Starter #1
I have a 540 that will be a 548 or 555 later this year. I am starting to get the parts together and was wondering two things:

1. Can you run a 6-71 or would it need to be at least and 8-71 to make some decent (IE up to 1300) hp.

2. How large of a blower can you have and still be able to use alky carbs. I know that the HP950's can be used up to about 1200 on a 540 with a 420 mega blower. Was just wondering where it runs out and can a 10-71 be run with carbs.
 

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question 1- on a motor that big run the largest blower you can
I'd consider a 10 a small blower
question 2- if running alky, and you should, put a injector and a pump and leave the carbs to gasoline. But you can run carbs on any blower, if looking to make the best power put it on alky
 

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Discussion Starter #3
Not looking for the most power but also will be index racing the motor. I don't want to have to constantly changing pills when the weather changes a few 100 feet DA, or change nozzels when it changes over 1000ft DA. The carbs will meter themselves based on the altitude; and I am willing to give up the tenth that an injector would be giving me for consistnacy.

Gas is not an option, Alky all the way.

Gas is for the generator, Alky is for racing !!!
 

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The carbs might meter themselves, but they aren't going to do you any favors on fuel distribution. Start getting into the larger blowers, and there's a lot of rotor in the back that the carbs don't cover. There's a reason there are fuel injection nozzles in the back of the larger blowers.

I don't think you're going to see as much of a variance as you think with injection.

Like Shawn said, on that big of a motor, a 10 would be the smallest.

Make sure the carbs are as big as you can get.... 1250s or larger.
 

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With the kind of racing you'll be doing it would not require changing pills or nozzels for weather adjustments. Alcohol has a very large window of tunning. For maximizing power for class racing, that's another story.

Blessings............Ron.
 

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The injector is the only way to go, one bypass jet is all you would change,
much easier than carbs, been there done that. Probably cheaper also
 

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RED ROCKET
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hey steve,my brothers 565 made 1375hp with an 871 and a hat..at 17% over..so an 871 would reach your goal hp wise.
 

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I kill parts
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An 8 is a good blower; we've made good power with one but on a little bitty stroke BBC. 17% isn't turning it none to hard neither.

If I were to go back to a "smaller" blower I would go with an inter-lock.
 

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Discussion Starter #10
Will, you got an 8-71 laying around? might need to talk to you about what your brother has and did. Might call you this evening.
 

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I have a nice polished littlefield 14-71, standard rotor set up for alcohol with a billet snout, its all fresh with new strips and bearings. Let it go for 1,800 with the snout.

P.m. sent
 

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Contact Pro Systems for your carbs. I am buildng a 598 with a 14-71 on gas and they recommend a pair of 1200 Doms. I was thinking I needed to go larger, but they said no.
 

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