Quadra-Jet rebuild

[Bill75]

My 75 has never been touched other that normal tune up stuff and the engine runs pretty poor at WOT. It caughs and skips pretty bad the more the secondaries are opened. I know the carb has never been serviced so I thought I'd rebuild it and adjust it to specs. I downloaded the article posted here by Lars, which I thought was excellent.
JEGS offers a rebuild kit for around $36 which to me sounds a little light on the $$ if it contains all the necessary jets, needle valves, etc. Any one had any experiences with rebuilding kits from them?? Any advice on doing this is appreciated.

Thanks, Bill

 

[citruspilot]

Well, I just did alot of work on my 79's engine, clean-up, painting, hoses, belts, carb. overhaul, etc. I had a freind of mine who is a master tech rebuild the carb with a kit from NAPA. I do not remember the name but the list price was about $45.00 but after discount I only paid $31.00.

Anyway, he rebuilt the carb with all the included parts in the kit and we installed it on the car. The car fired right up after a few cranks. However the more I drive the car I see that there is a rich running situation and the gas mileage has fallen to about 11 or 12 miles per gallon. Hell, it ran just fine before overhaul. I just overhauled it because it was 25 years old and looked like crap. It seems to runs ok just richer than before and an obviously large drop in mileage and smells richer too.......

I read the same article you referred too here and set the mixture screws at 3 1/2 turns but it still runs kinda weird and blows alot of black carbon out of the exhaust which is making my garage and driveway look bad......

My question is this. Are there some "other" adjustments that can be made without changing jets to make it run leaner??? The jets installed are the ones that it came with...........

Jeff

 

[Bill75]

Quadrajet

Hi Jeff,

Thanks for the reply. I never thought of NAPA, someone else told me the same thing today also. So I stopped by on my way home but have to go back tomorrow with the carb number. I must be brain dead, i was in NAPA the other day to get some plugs!!

Sorry to hear about your carb giving you problems. It might be something as simple as a torn or misplaced gasket or the floats too high. If it ran fine before, the carb and jets should be OK, something in the rebuild process wasen't quite right. I'm sure no expert on carbs though.

Best of luck, thanks
Bill

 

[brusso]

I read the same article you referred too here and set the mixture screws at 3 1/2 turns but it still runs kinda weird and blows alot of black carbon out of the exhaust which is making my garage and driveway look bad......

My question is this. Are there some "other" adjustments that can be made without changing jets to make it run leaner??? The jets installed are the ones that it came with...........

Jeff [/QUOTE]

I thought that the mixture screws should be set at roughly 2 1/4 turns. Then set to the best idle/vacume when warmed up. After all said and done you are still only at about 2 1/2 turns?

 

[citruspilot]

Brusso, I have the special tool used to set those darn set screws. My buddy told me to keep it and mess with the settings. Right now I believe they are set about 3 1/2 turns as the article mentioned. As I remember the author said that the adjustments should be at "3 1/2 turns" each and that is pretty much standard for those types of carbs. While setting them a week or two ago I closed them off, each seperatly, while the engine was running and nothing happened. The engine was cool though............

My question now is do they have anything to do with the higher RPM's fuel usage? I mean are they "idle set screws" or do they mix the fuel/air ratio thru the whole running range of the engine???? Can someone shed light on this subject?

I dont drive the car often enough to have messed with them too much yet. So as the warmer weather arrives I am sure I'll be out more on my days off trying different screw settings and report back.

For now have a great day!

Jeff

 

[Jack]

It's quite easy to accidentally bend the tips of the metering rods (aka intermediate needles). The metering rods are very thin and their tips are even thinner ... without close attention & care to making sure needles are square to jets, those tips can bend easily when trying to seat them into the primary jets (aka seats) ... especially when putting lid back onto carb. If the tips get bent they cannot fully seat and that'll cause over-rich condition. Here's a link to some helpful Qjet info: http://www.500cid.com/mts/tech/Quad.htm
JACK:gap

 

[Bill75]

Carb Numbers

Hey Jack,

I looked up the s/n of my Q-Jet (7045228) and it looks like it's not the origional. It's a California model (whatever that means) and also for an automatic car, mine is a 4 speed. Before I buy this rebuild kit is there something I should do to make this non-California or does that indicate something else?

Thanks,

Bill

 

[Jack]

HiYa Bill:
I honestly don't know how to answer. Hopefully someone else will chime in who has more direct knowledge and who knows if any of those differences really matter. It seems to me that it probably doesn't matter much ... BUT ... Given that I dunno what may or may not need changing ... dunno if it really matters or not ... here's what I'd be inclined to do:

I'd go ahead and rebuild the CA auto carb. If it runs OK after rebuild then I wouldn't worry about it. If it doesn't run OK then I'd be looking around (ebay, local junkyards) for a more correct "rebuildable" carb and then rebuild that one.
JACK:gap

 

[Bill75]

Ca. Carb

Hi JAck,

Thanks for the response and honest answer. Sounds like good advice. I sent for Doug Roe's book yesterday too, so maybe I can get a little more educated myself on this carb stuff.

Bill

 

[drags1998]

Ill try to remember all the questions, NO the idle mix. screws dont do anything at high speed!!! I will bet,the well plugs are leaking & the needle & seat or the float are not ajusted correctly!!! bottom line is, it has to come back apart!! Make sure whoever does it re-seals the well plugs with epoxy or JB Weld. If not youll be taking it apart again!!!!!:confused