Which carburetor?
Burning Brakes
Joined: Oct 2011
Posts: 956
Likes: 86
From: McDonough Georgia
My carb does not have a "kick in the seat" feel from engaging the secondaries - this is endemic of the secondary valves opening too quickly, usually from the air valve tension being too loose (shade tree hot rod trick, or just a worn 30 year old spring), or from the choke pull-off being blown or releasing too quickly. With these problems sorted, you don't have that 1-2 second gap which I'll agree with you as a very real number.
Another problem is that the bulk of them are calibrated quite lean from the factory, to the point that the secondary transition will cause a bog. No accelerator pump shot can safely make the gap that some of these quads have after being lean burn to start with, and then throwing ethanol blended gas into the mix. All of this can be fixed through experimentation.
It's sort of the opposite problem of a Holley; these were designed to run quite rich so no one's motor would burn up with an off the shelf calibration. You won't find a lot of dynosheet power by tuning them, but you will find throttle response and fuel economy. GM had the benefit of being able to tune unique castings for unique powertrain packages, and the handicap of having to have these cars pass smog. Engines that were never designed for it. Run 'em lean, throw a cat on and add ten other garbage systems to handle edge cases. Bleh. And 30 years later people are running stock calibration QuadraJets with gas that burns even leaner. It's no wonder they run like complete crap. Probably with worn out secondary cams and springs. A worn out secondary cam will limit the amount of fuel delivery to the secondary circuit (rods won't pull out as quick) and the spring, as mentioned before, will cause that lovely QuadraBog.
All of that said, I probably spent about 10 hours learning how to do my first QJet. Had it on and off the car 5 times or so playing with jets, rods, float levels and running it down the road. It now runs quite well and is more efficient than ever.
I would have had less time into a Holley for sure, but living in CA I'd have to go back to the QJ once every 2 years. Not to mention the headache of re-plumbing for those. Too much of a perfectionist to just run a rubber fuel line from pump to carb and snake it around for different carb setups. I also don't like engine fires.
Another problem is that the bulk of them are calibrated quite lean from the factory, to the point that the secondary transition will cause a bog. No accelerator pump shot can safely make the gap that some of these quads have after being lean burn to start with, and then throwing ethanol blended gas into the mix. All of this can be fixed through experimentation.
It's sort of the opposite problem of a Holley; these were designed to run quite rich so no one's motor would burn up with an off the shelf calibration. You won't find a lot of dynosheet power by tuning them, but you will find throttle response and fuel economy. GM had the benefit of being able to tune unique castings for unique powertrain packages, and the handicap of having to have these cars pass smog. Engines that were never designed for it. Run 'em lean, throw a cat on and add ten other garbage systems to handle edge cases. Bleh. And 30 years later people are running stock calibration QuadraJets with gas that burns even leaner. It's no wonder they run like complete crap. Probably with worn out secondary cams and springs. A worn out secondary cam will limit the amount of fuel delivery to the secondary circuit (rods won't pull out as quick) and the spring, as mentioned before, will cause that lovely QuadraBog.
All of that said, I probably spent about 10 hours learning how to do my first QJet. Had it on and off the car 5 times or so playing with jets, rods, float levels and running it down the road. It now runs quite well and is more efficient than ever.
I would have had less time into a Holley for sure, but living in CA I'd have to go back to the QJ once every 2 years. Not to mention the headache of re-plumbing for those. Too much of a perfectionist to just run a rubber fuel line from pump to carb and snake it around for different carb setups. I also don't like engine fires.
I agree essentially with all of the above. I don't know that the "kick in the seat" can be eliminated completely. You may not feel it, but that momentary transition will still affect the engine and performance.
As for the old Hot Rod tricks.....believe me, I'm familiar with those. To the point of guys reaming the jet orifices, filing the rods, cutting loops of the piston spring, and a slew of other BAD things.
Back in the day, there were two immediate modifications we wanted to make to grannys car so we wouldn't be embarrassed, a Holley and Headers. H and H.
Most of us couldn't afford them. So when GM started putting q junk in everything from granny's weekend driver to trucks they were plentiful. A 4 barrel in every pot.
Well, it didn't work that way, and still doesn't. As we all know each one has to be set up with the proper sized rods, spring tension, piston weight, cams etc. And quite frankly, a lot of q junks were butchered in the process of trying to make them run better.
None of that changes the fact that the float bowl is too small, they are inherently weakly built and the bodies deteriorate and warp, ridiculously complicated and designed to run lean.
As I've often said, the lean issue is a big one. The carb was never intended for performance. Yes, Pontiac put them in the ram air cars and others, but these were factory mods to eco cars to make them pseudo "hot rods".
When these carbs run really well, and when they are used in racing, they run rich. This negates everything it was designed for!!!!
Why in heavens name would you want those two small venturis and a small float bowl and all the complicated mechanicals, and hesitation when the carb is running a little rich now?
Throw on a Holley, or Eddy, or ANYTHING else that is simpler, and preforms better and be done with it.
Shark, you spent a lot of time figuring it out. I probably spent 10 years, wasted I might add, figuring them out. But you seem to enjoy it, so rock on
One final thought on the junk. Whenever a car acts up, it seems as if the first thing many guys do is fiddle with the carb. This is so wrong. 90% of the time it isn't. Diagnosing a car with a Holley is much easier than a q.
Your engine has to be perfect for the junk to operate properly. If the vacuum doesn't match the spring tension, or the idle is stumbling, or the distro isn't doing it's job then the q junk will not work right.
What do most guys do? Fiddle with the dang thing. They may even make it work a little better thinking it's "fixed". It isn't. The root issue is still there.
A Holley, or any other straight downdraft is much more tolerant of engine issues. It is easier to diagnose the motor and keep your car running well.
And for the record, I'm not a Holley rep. I just prefer them.
Lars is a stand up guy.
Last edited by commander_47; Aug 10, 2013 at 08:56 AM.
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Lars has rebuilt two q-jets for me. One for my '80 L48 and the other for the '69 L46 I had for a couple years. Both came back with repairs and improvements that I could not have made with just a rebuild kit. I think Lars bushed the throttle shafts on the L46 carb. On both carbs, he found bent/broken/missing parts that I would not have caught. On the L48 carb, the secondary metering rods were not quite perfect and he even sent a 2nd set to me for free to make it perfect.
If your distributor is original and you decide to have it rebuilt, Lars may be able to rebuild it. I am not sure if he still rebuilds distributors but he did a great job rebuilding the original distributor in my '69 L46 also. He road tests all work (he used his mid-year convertible to test mine if I recall correctly).
If your distributor is original and you decide to have it rebuilt, Lars may be able to rebuild it. I am not sure if he still rebuilds distributors but he did a great job rebuilding the original distributor in my '69 L46 also. He road tests all work (he used his mid-year convertible to test mine if I recall correctly).
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
I am not sure if we lost the OP along the way, but maybe you could list your best Holley model number (or whatever make) for the OP's setup. With that, he could decide for himself what path to take.
I believe he needs to drive the car and make a plan. If he goes out and spends money on a new carb now (stock), he could be stuck with that if he did other upgrades requiring more cfm.
I believe he needs to drive the car and make a plan. If he goes out and spends money on a new carb now (stock), he could be stuck with that if he did other upgrades requiring more cfm.
