Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Qjet 17057253 on a 380 Olds stroker
Cliff Ruggles:
HIC is for really hot climate/conditions where the engine is so heat soaked that it needs some additional air to speed up and help cool things down at idle, like stuck in traffic, for example.
In a cold climate you need a working crossover in the intake manifold, hopefully it's open.
Where is the float set, what size fuel inlet seat and how much fuel pressure?....Cliff
Seff:
Crossover is blocked. Aluminum intake ought to have decent heat transfer, once warmed up?
Float set to 1/4", fuel inlet seat is .135, using a factory fuel pump.
The changes to float and inlet made no difference to the issue. Would a vacuum leak cause such problems?
77cruiser:
How cold of a climate? Should have the cross over open & hot air off of the exhaust going to the air cleaner. If you only drive it down to freezing or so it'll be good but if colder, maybe not.
Cliff Ruggles:
Unblock the crossover and see if things improve some. Complete waste of time to run a cold intake on a dedicated street car. It's a wet-flow system and the heat is your friend with that sort of thing. Even GM used a heated intake on their TB engines well into the 1990's.
That will help your scenario, but I still think you have other issues. Right to start with the A/F ratio should go rich with increased throttle angle as you change the pressure differential above and below the throttle plates. By design the carb will fatten things up and the power piston raises to the highest position.
Make sure you have the correct length primary rods in it even if you got them here. One of my hired help some time ago tossed an entire order of 44B metering rods into the bin with our 44 late model tapered rods. A few sets went out before we caught the error.
Also verify metering rod height in the jets and make sure the PP arms are level and exactly even. Every single time we get a carb in here with similar issues the hanger arms are bent up, down, and never even.......Cliff
Seff:
I haven't unblocked the crossover, as the passage in both heads is filled up with poured aluminum. The temperature of the heads after a test drive was 182-185 F, the intake under the carb was 142 F, and the carb body itself was 125 F.
I measured the primary rods to 2.400" precisely, end to end.
The arms of the power piston were the same distance to the bottom of the power piston, so I assume they're straight as well.
Rods sit with the tapered part in the jet.
While looking for vacuum leaks, I noticed that idle picked up when I pulled a small vacuum hose. I got the engine to idle with 16"@850 by leaning out the mixture screws a quarter of a turn, but I couldn't replicate it after having turned the engine off and on again. I once again had 16" after having test driven, just when coming to a stop at a roundabout/traffic circle.
During the test drive, I noticed that the car would run at around 14.6-14.9 when cruising. When climbing a slight incline, or increasing speed, it'd lean out to about 15.5-15.9. This corresponds with a weaker vacuum signal compared to cruise. Adjusting APT moved the cruise AFR, but not the hill climb AFR.
Having found nothing wrong with rods or PP, I swapped the green PP spring for a light blue PP spring, but didn't have time to test drive.
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