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850 carb too much carb for my combo?

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Old 03-11-2007, 12:16 AM   #1
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Car: '91 Firebird
Engine: 305 TBI
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850 carb too much carb for my combo?

I have a .040 over 350 with ported 882 heads, victor jr, longtube headers, 1.6 roller rockers, 228/234 cam, 10:1 compression. Trans is a th350 w/2600stall and I have 4.56 gears w/posi. I shift at 6200. The carb is a 850 demon. I know for a fact that it's jetted way too rich. But is there any way I could just jet it down and tune it to work with my combo? If not, what size should I go to? Thanks.
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Old 03-11-2007, 12:19 AM   #2
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for the track there is no such thing as too big. For the street you'd probably be better off with a 650/750 carb, but that one could be tuned to work, but honestly those heads have to be killing your combo more than anything.
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Old 03-11-2007, 03:47 AM   #3
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Heh, same position I'm in. I'm putting my Demon 850 on the shelf and bought a used Demon 750. Just could not get the 850 to run right and perform like my old 750. Got it running great for a quick stab to half throttle but any more than that or just cruising around gave me problems. Been trying to work it out for 4 months with no luck.
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Old 03-11-2007, 06:55 AM   #4
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just think, i'm running a demon 750 on my 385 that i am shifting at 6500+.. you be the judge.. a 750 wil be more than enough
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Old 03-11-2007, 09:31 AM   #5
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I also vote for a 750. I think for your combo a 750 will be good for you for sreet and strip.
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Old 03-11-2007, 08:49 PM   #6
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Cool. Thanks guys, I'm gonna try a 750 on there this week.
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Old 03-11-2007, 09:28 PM   #7
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if any of you guys are looking to sell ur 850's my lil 454 is in need of a carb, pm me
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Old 03-12-2007, 12:23 AM   #8
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My 850 is staying with me for when I finally get around to building the 427 I have.
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Old 04-06-2007, 08:34 AM   #9
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Re: 850 carb too much carb for my combo?

Our carburetors are built more specifically than some other brands, so going too large is going to hurt performance.

It can lead to:
-Rich idle
-Poor Throttle Response
-Lean at WOT

On your combination a 750 would be the maximum we'd want to go, and depending on the rest of your specs you may want to go with a 650.
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