General Category > Quadrajet Carb Talk and Tips

Float level and other Qs

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Cliff Ruggles:
The "M" series rods are shorter and used in the later Q-jets with the APT system in front of the power piston.  For the most part they were used in the single main airbleed models with few exceptions......Cliff

Macadoo:
Okay, I have the '81 Checker Q-jet (M4MC) installed and it runs great!  Very crisp throttle and hard launches.  The idle is MUCH better now that the mating surfaces are all sealed up.  It is, however, dropping too much when put in gear; from 1100 in park to 700 in Drive.  The torque converter is a 2500 but the brand doesn't get great reviews (it came with my 200-4r).
For the carb, I used 74 jets with 56P rods which actually measured at 048 at the widest so maybe they were machined?  Half way down the taper they measured 44 so I raised the APT in an attempt to get that .030 range.  The only thing is; it pings at WOT, where as the Holley did not.  So I must be running a little lean.  Initial advance is right at 14* (recommended for my 455 setup) but I haven't checked "all-in" with the HEI.  Truth be told, I haven't had the guts to stand next to this engine I built myself with it running at 4k RPM  :-[
I'm wondering if your modified primary rods would be a better/richer fit.

Cliff Ruggles:
P metering rods should taper apprx .010" on the upper section unless they are worn down some.

I do NOT put used metering rods into our builds here, most are worn down and often flat-sided, and the jets are typically "egged" out some as well.

Pinging at WOT could be sucking the bowl low and going lean, may not be a tuning issue.

Our "M" series metering rods are full taper with .036" tips and designed to be used in the later model single MAB models.......Cliff

Macadoo:
The 74 jets I bought new last summer and never installed.  The rods are questionable, as they came with the "rebuilt" carb.
I'll replace the rods and play with the fuel pressure.
Thanks for your patience, Cliff.  I'm happy with my progress.

Macadoo:
Okay, well, this is embarrassing but I was told at a car show that I was cranking down on the distributor bolt too hard.  I went out this morning to figure out the pinging and the bolt was loose and the dizzy had jumped forward.
I started from scratch, set the initial at 14* with vac disconnected, played with the fuel mixture screws for best vacuum, and locked it all down.
I went out for a test, shifted from 1st to 2nd (200-4r) and hammered it.  The darn thing broke loose at the 2-3 shift!  I laid a short patch in 3rd gear so I must be getting close.
Cliff, would the shipping really be just $5 for a couple rods?  I'm looking at the 44s and maybe the secondary rods.

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