Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Engine suddenly running terrible

<< < (3/5) > >>

ourkid2000:
Thx Cliff.

Jeez, I just got this thing back from the rebuilders......like it's had fuel in it for a month, tops. I only buy the non ethanol Premium that is available near me.

Cliff Ruggles:
Avoiding ethanol is NOT going to help.  Those POS "O" rings on the drive-in bypass plug are ALWAYS leaking when those carbs show up here (at least WAY back when I took them in). 

I wouldn't touch one these days with a 200' pole, simply because they have fundamental issues that are difficult if not near impossible to get past.

The secondary dampening system is HOPELESS, and why all Q-jets got the BAD reputation for "bogging" when going to full throttle.

The fuel inlet valves were HOPELESS, and why the factory very quickly went to a screw in N/S assembly by 1967.  Ya, I know and before someone slams me they continued with that design into 1967 on a few part numbers, but not too many.  The replacement N/S assemblies to "upgrade" the inlet valves and block the bypass are WAY too small to allow enough fuel into the bowl with high HP set-ups. This fundamental issue is why ALL Q-jets get an undeserved reputation for NOT liking high fuel pressure and float bowl "too small" for high performance use.

Those carb leak at just about every lead or brass plug in them, another issue corrected by 1969 when the factory made the castings thicker and pressed in aluminum plugs and swaged over them.  This fact has EVERYONE on every Forum, blog, etc telling you to smear a bunch of JB Weld over bottom plugs that were NOT leaking in the first place on the 1969 and newer units.

The poorly located hinge pin is HORRIBLE for fuel control and upgraded in 1969 to a far superior design with a much smaller float.  Folks that "rebuild" early carburetor with the short hinge pin are STOOPID enough to still use brass floats in them, see it done all the time.  HOPELESS scenario there no matter what anyone tells you.

Even with all that said with enough effort, correct parts and knowledge of the shortcomings of the 65-66 Quadrajets you can get them to work OK with enough effort.  They are NEVER going to be nearly as good as a later unit, difficult if not near impossible to keep up with anything making big power or a fast vehicle, but for a daily driver to and from Dairy Queen or a local car cruise you'd be OK with one.......FWIW.....

ourkid2000:
Thx Cliff,

I get it, these carbs aren't great I know, but put me in the Dairy Queen category.

Doing what you suggest with a later carb is no small venture. That's a $1000, minimum operation and I'm just trying to get this car back on the road. One thing at a time right? Maybe in a couple years I can get a fancy new carb built for me, but not yet. I've got some body work and a paint job to do which is probably going to come first.

Also, I've got 2 1966 carbs for this car and I will soon have the better part of a 3rd carb so between the three of them, I should have something that will work. One of your colleagues has put together a 66' air horn/float bowl combo for me with all the major flaws addressed. I'm pretty pumped about this and I can't wait for it to arrive.

In the meantime, I have a serious intermittent running problem that I'm having issues narrowing down and I'm really not sure where to start.

ourkid2000:

--- Quote from: Kenth on April 13, 2023, 12:16:04 AM ---Have the leaking bottom plugs in float bowl been fixed?

--- End quote ---

Yes they were sealed up by the rebuilder back in January.

Kenth:

--- Quote from: ourkid2000 on April 14, 2023, 10:33:13 AM ---Yes they were sealed up by the rebuilder back in January.

--- End quote ---

By "fixed" i mean, did they knock the brass plugs out, thread the holes and installed threaded plugs with some thread sealer OR did they put on some epoxy around the leaking brass plugs (short term fix that will never hold up for long).

Navigation

[0] Message Index

[#] Next page

[*] Previous page