From what I've seen, Holleys can be "an acquired taste" of sorts. I'm not sure why, but back in the 1960s and 1970s, I heard lots of complaints about anything Holley from Chrysler people, but as the 3310 780cfm 4bbl was on the high-level Chevy performance engines of those times, never heard anything bad about Holleys from them, by comparison.
By the middle 1970s, I had been around some Chrysler people to ask questions as to what was wrong with Holleys, considering they were supposed to be the premier high-perf and tunable carb of those times. I heard about gasket issues, mainly. It seemed that people who knew to buy quality parts and carb kits from the right places (Holley, specifically) usually had no issues with them, but people who did not understand them did have issues.
THEN the local Chrysler dealer service manager summed it up well . . . anything with a OEM Holley 4bbl usually needed a rebuild kit once a year, along with the normal tune-up, just to keep things going well. By comparison, the OEM AFBs and AVSs were "rebuild them and forget about them", which their Chrysler customers liked, so if the particular car had an OEM Holley, when it started to cause problems, they'd get a similar OEM AFB and install it. Customer happy!
Now, let's jump up into the 1990s, I bought a new 4160 OEM Replacement for an engine I was upgrading. No issues of any kind, except by the time I needed to pull it apart and such, I was wanting a new 4175 Spreadbore, again OEM Replacement. I ran that carb for many 100K miles with no issues of gasket leaks or similar. I did replace an accel pump diaphram after ethanol'd fuels became common. Other than that, after tuning the secondary spring (with the Holley kit), it performed great and upped my mpg about 2mpg on the highway. No leaks, especially after it seems their new gaskets glue things together. Only thing I've been able to remove easily are the float bowls as the metering block is glued to the main body. Very well glued!
My '70 Monaco 383 4bbl had an OEM AVS on it. No issues. My '67 Newport 383 4bbl had an OEM AFB on it, with no aux air valve in the secondaries, for full manual secondaries. No issues. I later added a different intake and a 9801 TQuad to the '67 Chrysler. Not impressed as no increase in fuel economy or power, although it was claimed that carb was calibrated for a 383 4bbl engine.
I've had both brands and had no issues with either one. By comparison, the Holley has lots more parts in them. First time I saw an old Chrysler AFB apart, I wondered where all of the "other parts" were. I later learned there were no missing parts in that AFB, just that Holleys had many more, which made them much more tunable for non-OEM modified engines. Which was Holley's strong suit in the racing community, street or track.
At this point in time, the older OEM Replacement Holleys have been replaced with newer "lines" of carburetors which are completely aftermarket. Many can get close to the older OEM carbs, but seem to have 'gimicks' the older ones did not. It seems that one can get "in trouble" easier with these newer Holleys, following "tricks" others tell them about "that worked for them". Especially on the square-bore models.
Now that the newer AVS2 carbs are around, that's my new favorite 4bbl.
When the then-new Thunder Series AVS was introduced, it had the normal GM-style throttle hookup, for which the Chrysler adapter bracket was needed. I sent Edelbrock an email suggesting that they build ONE part number specifically for a 1969 Chrysler 440HP application, as an OEM replacement. I got no response back or saw evidence they were moving in that direction. Oh well . . .
Enjoy!
CBODY67
