I have a stock L-48 with the origibnal Q-Jet. However, ever since I bought it, it has been running a little rich. Isn't there a simple, basic procedure for a simple adjustment on the carb?

I had read some where that you turn the air mixture screw inward, (clockwise), until the engine started to "stumble", then back it off counterclockwise 1 1/2 turns. Same procedure for each adjustment screw.

Does this sound right?

 

Rich at idle? Cruise? WOT?

The idle mixture adjustments won't impact much besides idle. Might check your choke first,..make sure it's opening all the way and you may want it to open sooner.

 

How do you know it's rich? Do you smell gas?

The Q-Jets have two idle mixture screws...one for each side and if you don't know carbs it might be a good idea to leave them be if they still have the plastic lock caps on them.

If you like doing the mechanic kind of thing then go ahead and buy a rebuild kit...you will need the part # on the side of the carb for the correct kit: http://www.partsamerica.com/ProductL...Carburetor+Kit
, and a parts dip can with basket for $20 like this: http://www.partsamerica.com/ProductL...=Parts+Cleaner

I also bought a stainless steel 20 Quart stock pot like this one: http://www.qvc.com/asp/frameset.asp?aol_refer=false&msn_refer=f alse&nest=http://www.qvc.com/scripts/detail.dll?item=K180832!tpl=DETAIL!ref=C J4&ref=CJ4&

and the 5 gallon can of Berryman's B9 since the carb body won't fit all the way into the 1 gallon $20 can.

The instructions which come with the kit help explain everything you need to know about carburators in order to properly adjust it. Carbs sometimes just need some cleaning and new gaskets & seals to get them running good.

So, for about $100 you can completely rebuild your carb and learn everything you need to know so you can adjust your carb yourself. It's much cheaper than buying a rebuilt carb or having a shop do the work.

 

Are you sure its the original carb?
Can you post the stamped # on the throttle linkage side?
It should start with 170 and be 8 digits long

Also look for any paper stickers on it which commercial rebuilders usually affix somewhere.

 

Hi Guys,

I appreciate all the above responses, but no one has asnwered my question.

I know it's runnng rich because you have a very heavy gas smell at idle, it you have to race it up and hold it for a second to "clear it out", and then it runs fine. If you stand behind it your eyes will start to water from all the raw gas coming out of the exhaust. Alos, if you follw behind her when someone steps into the gas really hard, it puffs out a quick black smoke puff, (NOT blue which would be oil burning), but blacjk as if it was running rich. It's not the choke, as the choke would make it completely die out as it would eventually overload with gas. The plugs are slighlty blackened / sutty, which also indicates a rich mixture. Lastly, if you romp down on her hard from an idle, it takse a moment for it to overcome the gas overload. All these are signs of a too rich mixture.

The plastic lock cap covers are already gone.

The carb doesn't act like it needs rebuilt, it acts like it needs adjusting. Two very different needs.

I am uncertain if this is THE original carb for my engine, but it IS an original STYLE Quadrajet as used on the 1976 L-48's. Evereything else on teh car is matching numbers right down to the A/C compressor and the xcar only has 60K miles, so it mostlikely IS the original carb.

I appreciate all the above responses, but no one has asnwered my question.

 

If it is just a idle problem you should be able to adjust it out with the mixture screws if the rest of the idle circuit is in good working order.

Start with connecting a vac gauge to manifold and adjust the idle mixture symmetrically to max vacuum @ ~850rpm idle speed. If you still have the rich symtpoms you may have other problems.

Make sure your timing is set corretly before you start on the carb adjustments.

Hope this helps.

 

But the idle mixture screws are exactly that..Idle mixture, as soon as you crack the throttle the idle screws have zero effect on the way it runs anymore

Perhaps it's jetted too rich
I would pull the air horn off and see what primary jets and rods are installed and check the float level.

Certainly do the vacuum test first, a stock L-48 should be in the 20" range @ about 750-800 rpm and check the timing as well.
Did you check the stamped ID on the carb to make certain that it is indeed a 76'?
And you diddnt say if it had any stickers on it either.

 

1) With the engine off, gently turn each air mixture screw inward (clockwise) until they stop. Then back them both out (counterclockwise) exactly 3 turns.

2) Attach your vacuum gage to the intake of the manifold.

3) Start your engine. Adjust the mixture screws inward 1/2 turn at a time until the idle begins to become rough and the vacuum begins to dip lower. Then adjust that screw outward by 1/4 to 1/2 turn until the idle smooths out and the vacuum is high again. Use the same procedure for the other mixture screw.

4) Ideally, both mixture screws should end up at about the same number of turns outward (give or take 1/2 turn) when you are finished.