Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Idle problem
Cliff Ruggles:
With 15" vacuum at idle any PP spring will be down. The stronger ones lift the rods earlier, and can improve throttle response slightly with some set-ups.
The orange spring should be fine for what you are doing, but you may be able to make improvements tuning in that area.....Cliff
dlphil10:
So I shaved the deck down 0.020" and went to an 0.040" over bore, but same heads and cam. It should be around 8.8:1 - 9.0:1 SCR. I know thats still a large cam for the setup, but I would have expected different results.
I am now getting around 11inHg in park and if I put it in gear it dies. If I put my hand over the carb it picks up rpms and will make ~15inHg. Sounds like I should replace idle tubes again with larger ones and drill out DCRs? Can DCRs and idle tubes be englarged while they're installed? Would the carb sitting for a year and a half cause issues?
Cliff Ruggles:
They make long precision bits to drill idle tubes in place. Dcr's are easily accessed to no problem opening them up a tad in place.
Sitting shouldn't be an issue unless a mud-dabber crawl into it and muddied it up some......
dlphil10:
Alright so I went through the carb and changed the idle tubes to the 0.037" ones you sent (thanks!)
It idles so much better at around 12-13inHg, but we took it for a drive and it will NOT accelerate... Heavy and medium throttle makes it slow down. It only wants to speed up with light throttle and very slowly at that. Do you have any ideas on whats wrong?
Air horn idle bleeds are ~ 0.050"
Air horn main bleeds are ~ 0.070"
Lower air bleeds are ~0.070"
DCRs are ~0.050"
Mixture screw holes are ~.100" (They were like this already)
Accelerated pump hole ~0.027"
Orange power piston
42 rods and 72 jets
Float ~0.25"
Cliff Ruggles:
Power piston stuck or hanger bent down to keep the rods from coming up out of the jets high enough??
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