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Calibration of 800cfm unit for mild 350 Chevy

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carmantx:
You are getting good suggestions, but aren't helping yourself.  What carb are you working with?  What are the current calibrations? 
Build the entire carb for your engine is best thing to do, not just change some jets.

anvilhandsmagillacutty:
Really?? So, buying the book will tell me EXACTLY which jet/rod combination to use with my particular engine/vehicle/drivetrain? And, the idle/off idle modification I've been advised of, will provide the ideal air/fuel ratio through the venturi/main system for all throttle positions, after idle/transition circuit has exceeded it's design limitations? Even at sustained W.O.T conditions...and provide my engine with the proper mixture to avoid lean out, potentially damaging detonation, or economy destroying/power robbing richness? Wow! I don't see what carb number, or original factory application, plays in jet/rod selection for use on a modified non original engine/vehicle, with far different fuel requirements than how it started out. For example, having none of the factory emissions equipment, EGR, AIR, THERMAC, CATALYST..etc. Seriously, I'm really only looking for replies from someone who has a known, proven combination, on a Chevy 350 or similar size Chevy small block with the large primary carb. All other advice is unnecessary. I'm not looking to get into web arguments, or serious debates over opinions either. My question is titled calibration, but I'm referring to main metering calibration. As I stated previously, I'm NOT going into idle restriction modification AT THIS TIME. This carb will be getting used on the 383 roller cam motor I'm currently building, which will also be using a 125 horsepower PowerShot plate system. That's why I'm not doing anything permanent with idle restrictions now. Thanks anyway.

Frank400:
Primary calibration is not only determined by jet and metering rod.  A HUGE part of it is main air bleed size.  So let's say a 72jet/42 rod combo can be pig rich in one carb (carb number that is) and ultra lean in another one, same engine on both. 

   The idle system also is an important player here, as it's still doing work when the primary main system is working.   

  It's not as simple as "let me know which jets and rods".  The book will tell you HOW to get the correct recipe for your car.  Or just buy a complete carb kit from Cliff (NOT an auto parts store kit !) and if you're willing to tell him your carb number, he'll probably get you in the ballpark for what you want to do.  That is IF you're willing to give him your carb number.

anvilhandsmagillacutty:
 Well alright then!! Consider me thoroughly humbled, AND thankful for that last reply. That explains alot. Especially, the inconsistencies with sizes in correlation to displacement of intended engine family. So, what youre saying here is, the AIR pickup in the air horn, will be sized for the intended engine. Therefore making one size jet, not always providing similar results in a carb with larger/smaller air pickup? BTW, the particular carb I am using is off a 425 Caddy. #17085239. I do not know of the original configuration, as it was gone before I got it. The carb is in very good shape, which is why I used it. I have, however...substituted the Caddy base with a Chevy base that has old type non "tamper proof" mixture screws.
Other than the lack of the third attaching screw, I don't see any problem. But, do you see an idle passage issue with this base?

anvilhandsmagillacutty:
Wait a minute, now. It seems the identification information here is incorrect, at least with my carb. This says my carb is 1985 Caddy with manual transmission. If it was any GM car AFTER 1980, it would be ECM controlled, so I can't see that being right. Also, this carb number came up in MULTIPLE web search results, INCLUDING a GM parts book....as 1985 GMC/Chevrolet 5.0L federal manual trans!!! Looks like my question has been answered, by MYSELF! I will leave the idle circuit, and everything else as is...and simply run the 5.0L or 5.7L calibration. I guess GOD really does help those THAT HELP THEMSELVES!!!  8)

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