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  #1 (permalink)  
Old 10-08-2006, 05:03 PM
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Default Carb recamendations

I currently have a pair of Holley #1850 600 cfm carbs that are highly modified and have no choke towers. This is on an inline dual four setup on a 427 FE. With winter temperatures dropping a set of a carbs with manual choke will be desired. There has been some descusion about not having enough vacume to open the secondaries at any achievable RPM with the 600 CFM #1850 carbruetors. Holley carb numbers I know about are the vacume secondary carbs #1850 600 cfm, #1848 465 cfm, #8007 390 cfm and the Holley #9776 450 cfm is a manual secondary carb but doesn't have a choke. Is there a manual secondary carb with a choke to go with the Holley #9776 ? Pros and cons please, suggestions. cost is an ingredient in this choice.
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Old 10-08-2006, 08:37 PM
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What kind of operating rpm range will the engine see?
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Old 10-09-2006, 12:20 AM
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Quote:
Originally Posted by Michael C Henry
...There has been some discussion about not having enough vacume to open the secondaries at any achievable RPM with the 600 CFM #1850 carbruetors...
The air flowing through the primary venturi flows by a hole leading to the secondary diaphragm. The air flowing through the primary venturi pulls vacuum through this hole, opening the secondaries. Engine vacuum has nothing to do with it, just the speed of air through the primaries. You’ve got to have enough speed through both carb venturies in order for the secondaries to open if they’re connected with a hose.

Dan
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Old 10-09-2006, 01:55 AM
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They made a racing movie called redline 7000. original 3.78 inch stroke and ARP rod bolts. I once twisted a 406 to around 8400 rpm one eveninging 1968 and wiped out one or more rod bearings and then the engine the next day.
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Last edited by Michael C Henry; 10-27-2006 at 05:58 PM..
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Old 10-09-2006, 07:44 AM
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If it runs well with your current setup, leave it.

It just takes a few more minutes to warm the car.

If you want, you can increase the idle circuit a few hundred rpms.
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Old 10-09-2006, 10:01 PM
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As the weather is getting cooler, starting is getting harder . Also once started warm up must be done without much razing the throttle. It's only 55° now wait untill temps reach 40° or lower. A manual choke would make all kinds of differencs. Yea it runs great once warmed up.
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Old 10-10-2006, 05:54 AM
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Because the air is more dense you will have to add more fuel on cold ambient air startups.
Once engine fires hold the throttle at 2k (minute or two) until engine runs by itself, again if you have to, increase the idle circuit.
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Old 10-12-2006, 07:08 AM
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I have a 427 side soiler with an original Ford intake for dual carb's. I am looking for carb recomendations for this arrangement. I do not want to "over-carb". I was looking at two Holley 600cfm.
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Old 10-12-2006, 09:42 AM
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Dan,


A guideline................
To calculate what your engine needs with respect to CFM:

.

CFM: Engine Displacement (cu. in) X Max RPM
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3456

.
.

Round up to the next carb size if just above/below rating.
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Last edited by bret a ewing; 10-12-2006 at 09:45 AM..
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Old 10-26-2006, 04:41 PM
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The carbs catalog on the Holley.com, pages 24 and 25 (pdf pages 18 & 19) has a basic guideline for carb selection, that will do just fine in most cases. I suppose they know what they are talking about. The catalog has all sorts of basic info on carburetted systems, very informative.

http://www.holley.com/data/Catalogs/...arburetion.pdf
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Old 11-01-2006, 10:43 PM
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The manual choke will need an air horn which will not work well with your air cleaners, I checked your photos. I throw a towel over my air cleaners to start. I have a hard top and heater and drive it year round in both snow and rain although I try hard to limit both. Even a little snow is a complete loss of friction and cobra wipers suck.
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