Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Quadrajet running lean after head and cam swap

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bcarlson78248:
Cliff - called today, but they told me you wouldn't be in until tomorrow, so I will call tomorrow morning.

Thanks,

Bruce

Repeating the engine and carburetor info.
Engine upgrades in July 2018
- Blueprint aluminum 195cc heads, 2.02 intake, 1.60 exhaust, 64cc chambers
- .026 Mehle head gaskets to increase compression to ~ 9.4 compression ratio
- Edelbrock dual plane intake
- Howards roller cam 213/217 @ .050, 112 LSA, lift 0.485 int/0.495 exh
- AC delco 41-629 plugs, gapped at .040
- Cast iron manifolds and full duals
- TH350 with stock converter, 4.10 gears, 31" tires
- Truck weight ~ 4800-5000 lbs
- Quadrajet (17080213 Q243 CPX)

Timing
- Initial timing 12 degrees BTDC
- Centrifugal adds 20 degrees by 2200 rpm
- Vacuum advance adds 17 degrees
 
Current Quadrajet setup
- Quadrajet (17080213 Q243 CPX)
float - 1/4"
Power Piston Spring - dark blue
Jets #73 (stock)
Primary rods - unknown
Secondary hanger - G,  33797  .545", 2nd shortest
Secondary rods - DP, - leanest (686)
Accelerator pump - 2nd hole

Cliff Ruggles:
We got in late yesterday, took a long weekend to go to a wedding out of town.  Will be in the shop the rest of the day.......Cliff

bcarlson78248:
Cliff,

I was out of town, so I just got back and opened the parts package you sent for my Quadrajet - 17080213 Q243 CPX.  Now I've got it apart and am installing the parts you sent.

I have quite a few questions, so please bear with me.

- Jets are #74 vs. the original #73, so a little bigger.
- I removed one of the idle air bleeds and found that it measured .032, but the new ones you sent are .030.  I expected them to be bigger, maybe as much as .037.  Did I get the right ones?  Or should I just drill these out a little bigger?

- Power piston is orange/red vice the dark blue I had before. Which spring do you think will work better?  It looks like  moving to the orange spring would make sense for smoothing out the power transition.  However, I still get about 19" of vacuum at idle with this 213/217 @ .050, 112 LSA cam. 

- I set the APT 2 1/2 turns out for now.  Any suggestions about whether this should be changed?

- New Secondary rods are DA (.0440 tip), originals were DP
- Primary rods are:
old ones measure at .049, tapering to .034,marked 49Y
new ones measure at .050, tapering to .038 (marked as 50C). 
Would I be better off leaving the old ones in for a stronger power mode, or would it get too rich in power mode when combined with the #74 jets?

I've got the float set at 1/4" right now.  Any reason to change?

Thanks for your help.  I appreciate any input you have.

Bruce

Cliff Ruggles:
Removing airbleeds at .032"?  Hoping you are referring to the idle tubes.

Yes, we don't pre-drill the idle tubes unless requested, so open them up some.

This will bring in more fuel to idle, off idle and transition.  It also feeds the main system.

Use the jets, metering rods and PP spring provided with the larger idle tubes and make sure the DCR's are at least .055".

Do some testing, use the APT system to fine tune, and see where things are at......Cliff

bcarlson78248:
My error - new idle tubes measured at .030, so I will drill them out to .037.

DCR - i

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