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« Last post by cal30sniper on January 22, 2021, 07:27:18 AM »
I’m looking for some feedback on which of the following carb cores I have on hand will make the best rebuild candidate. Both carbs are complete and fully functional, but both have been sitting for quite some time and both are in need of a full rebuild. I plan to use Cliff’s HP kit on whichever carb I select.
First, the application:
-3200lb 1977 Plymouth, manual brakes, manual steering, no A/C
-318 factory roller cam motor, swirlport 302 heads, 9.2:1 compression ratio
-Lunati 20200714 hydraulic roller grind (207/213 duration at .050, 258/264 advertised, .485/.485”” lift, 112LSA)
-Magnum exhaust manifolds (think small headers) with free-flowing 2.5” dual exhaust
-Weiand 4bbl spreadbore intake (Action Plus) with 1” phenolic carb spacer and heat shield
-Early magnum air cleaner with ducting to fenderwell inlet
-46RH overdrive auto with lockup converter and 3.55:1 rear gears
I estimate the combo will be around 275 crank hp with near factory idle characteristics (should be 14+Hg at idle with a slight lope). Application is a commuter that will see 70-80 miles of mixed highway and city driving daily. Altitude here is 5500’, and it will rarely if ever see altitude below that. It may see up to 8-10k’ on occasion, but not on a regular basis. The car regularly sees morning start temps of 20F or below during winter operation. I will be maintaining the hot air crossover under the intake due to these cold operating conditions. The Magnum manifolds I’m using don’t have provisions for air cleaner heat, but I may add a hookup to use the hot air tube and vacuum controls for air cleaner heat during winter operation. It also sees high 90s and occasionally low hundreds during summer operation (high desert environment – hence the phenolic spacer and heat shield).
The carbs in question (please excuse my rough measurements, still waiting on some bits to come in):
1. 1985 Mopar non-CCC Quadrajet 17085408-1994 (should have been used on a 360 4bbl truck)
a. Chevy-style Single Main Air Bleed carb (.080-.090” main air bleed size)
b. Mopar throttle linkage primary shaft (required for my application)
c. Electric Choke with rear pulloff only
d. 72 Jets / 54M Rods
e. EA Secondary Rods on L Hanger
f. Idle Air Bypass ~0.050”
g. Carb has clearly been into before, but the work seems quality (bushed primary shaft, threaded APT adjustment plug, brass float, no marred fasteners or other nonsense)
2. 1977 Olds Quadrajet 17057553-3146 (I believe this came off a 350 olds)
a. front inlet dual main air bleed carb (~.070” for upper/lower main air bleeds)
b. Hot air choke with dual choke pull-off (adjustable front pull-off) and slotted secondary air flap shaft
c. 74 Jets / 48M Rods
d. CV Secondary Rods on F Hanger
e. No idle bypass (passages are present but not drilled through baseplate, I believe this is due to the hot air choke functioning as a form of idle air bypass)
f. No indication that the carb has been rebuilt or modified before
g. Has “idle-stop” solenoid on front driver’s corner
(Part 1 of 2)