Classic Mustangs (Tech) Technical discussions about the Mustangs of yester-year.

Carb size 750 or 850?

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Old Oct 9, 2010 | 09:24 AM
  #1  
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GT350son
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Default Carb size 750 or 850?

I'm building a 347 stroker with
225cc AFR Heads
Lunati Cam retrofit - Duration 300 int / 310 exh, Lift .560 int /.576 exh
Edelbrock Performer Air-Gap

And would like to know what size holley carb you guys suggest.
Its going to be a street/heavy strip car
Thank you in advanced
Old Oct 9, 2010 | 09:39 AM
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Well, the 750 should be enough unless you plan to exceed 8000 rpm. The 850 would get you to 9000, if your pistons didn't come through the hood first.

Bear in mind, the smaller the carb, the better the throttle response. If this will be a street driver, you'd be better off with a 650.
Old Oct 9, 2010 | 09:58 AM
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Okay thanks I was thinking a 750 DP, I will try the 650 first since I already have one on the engine I'm replacing.
Old Oct 9, 2010 | 09:59 AM
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Agreed. I have a 600 Edelbrock on my 331 and it works well. I may upgrade to a 650 Demon or QuickFuel in the future, but for now my 600 gets the motor to 6200 rpm just fine. If you're doing mostly strip, I'm sure the 750 would be more than enough.
Old Oct 9, 2010 | 12:43 PM
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What are the specs on the cam, and is it a roller cam?

I run a mechanical 650 Quick Fuel on my 302....with annular boosters could have gone 750.

A 347 with heads that big really would work best with a lot of cam, and would then need at least a 750. 850 annular and light internals and throttle response will be great.
Old Oct 9, 2010 | 01:29 PM
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here's the link on summit
Lunati 55118LUN
Old Oct 9, 2010 | 04:49 PM
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Thinking about it, I have a 351W with a cam close to yours. I run a 625 Carter Comp and it's great to 6K. 99% of people over carb cuz they think, bigger is better, WRONG! When I was at B&M, we sold a 750 cfm for the blown engines. This is a chart that I have found to be very useful throughout the years, hope it helps you.

Old Oct 9, 2010 | 06:55 PM
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That chart probably is best at or near sea level. At higher elevations, more cfm and tuning can help make up for less O2.
Old Oct 9, 2010 | 07:46 PM
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yeah. im at like 500-1000ft so its basically sea level
Old Oct 10, 2010 | 10:37 AM
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well i think we all agree on 750ish with that setup. I heard plenty of times that you can go way bigger without sacrificing throttle response when using annular boosters. carbs have improved over the last 40 years. my 302 with a 650 demon doesn't seem to have any overcarbing problems



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