General Category > Quadrajet Carb Talk and Tips

Calibration of 800cfm unit for mild 350 Chevy

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anvilhandsmagillacutty:
Hello guys. I have a mild 350 Chevy in my 55 sedan in front of a 700r4 transmission with 2500 stall lockup converter and 4:10 rear end gears. The motor is a dished piston Goodwrench short block with 58cc 1.84" 305 heads, a competition cams 268H, aluminum Quadrajet intake, dual snorkle Z28 air cleaner with tall lid, E-1500 K&N, and 1 5/8" mid length Patriot headers running into 2 1/2" super turbos. My question pertains to the primary jetting/rods to use in this Bigger 800 carb to make the small block fuel ratio correct. I have on hand many jets, rods and hangers. But, am conflicted about where to ballpark it.

blazer74:
First step is to get Cliffs quadrajet book.

Also a description of what carb number and what's been done to it as far a you know first.

anvilhandsmagillacutty:
I don't really want to get into much modification of the basic design right now. I just need someone with first hand experience using the large primary carb on a smaller displacement engine, to give me some starting point with jetting. In other words, what they are/were using. For example, what main jet number and rod will get me out of excessive richness, if any(that is, if the B.B. calibration is not already suitable). I don't have a problem tuning it once it's drivable, but sure would love to start off in the right direction. Thanks

Frank400:
  Hopefully some people with more experience than me will chime in, but here are my suggestions.

A carb number would really help, I'm guessing you have large (.120") main air bleeds.  If so,  I'd suggest downsizing them to .070" (both), and going with a 71 or 72 main jet, along with Cliff's .044" full taper metering rod. 

    The idle/off idle definitely will need some attention too, I'd say as important as the primary main system. 

anvilhandsmagillacutty:
Here are some various jet/rod combinations I have pulled out of swap meet carbs. These are all late 800 apt type carbs with Chevy style bellcranks. 454: 72 jet w/ 49M rods (DR rods/N hanger). 5.0L: 72 jet w/ 50M rods (CP rods/N hanger). 5.7L: 73 jet w/ 49M rods. Misc. 800: 74 jets w/55M rods (EH rods/E hanger). Out of all these primary combinations, which would suit the mild 350? Or, a combination thereof? Once again, we're only speaking if main metering here. Idle circuit, I'll delve into later on.

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