What do you guys think, does the Valvoline guide have it right?

http://www.valvoline.com/carcare/art...cid=5&scccid=5

http://www.valvoline.com/carcare/tip...es&tipNumber=2

 

Unless you have skills and a milling machine some of this you cannot do or should do.Whoever done this was after a performance gain as well as a rebuild. They also had a lot of experience at modifying carburetors. If your throttle plates and shafts are fine and you are after a stock rebuild you can clean and replace parts and seal up the fuel wells and get some more miles out of your carb. If you are needing more done as shown expect to pay more than you would for a new 750 holley or edelbrock.I can't fault what was done in the step by step instructions as it looked to be done with skill. I just wonder for a street driven car that it is all necessary.

 

First, I have not read and looked at all that was there, but I'm sure there was good info. Sometimes good info can make things seem daunting (you don't need an x-ray machine to find problems in your casting). Rebuilding a carb to stock or high performance specs is not difficult, you just need to know what you are doing. Obviously, you need to know more for a high performance rebuild. You learn by reading stuff like this (and Dour Roe and Cliff Ruggles books and Lars' articles). You will find the experts do not agree on everything, so try things for yourself and find out what works. It can be fun and rewarding.

God bless, Sensei

 

or you could just send it to this guy and get a good job done!

 

If you pm me your e-mail address, I can send you the latest revisions of Lars Q-Jet rebuild and tuning papers.

 

Sent you a PM.

 

For the most part my engine seems to run fine for a wussy L48 but when I hit the accelerator hard it bogs down/hesitates at first and then after light pull back and pressing accelerator again the 4 BBLs eventually kick in, then zoom. I'm guessing it's either time for a rebuild, a good cleaning, or possibly modifications are needed. There's enough varnish build up for a 78 and has never been rebuilt. I'm thinking possibly one of the jets might be clogged as the reason for hesitation?

 

First off check your timing. It may not be the carb after all. But it wont hurt to go through the thing anyway. I had no knowledge about carbs but I used Lars' papers and Cliff Ruggles book along with his high performance carb kit.

It all sounds complicated, but once you start tearing it apart, you understand what things are and what they do pretty quick.

Sean

 

When I need a q jet to pass smog, I got an old body and sent it to the
"Carb Shop" for rebuild. This was a few years ago, but it cost about
$250. After that it was like FI. I would pump the gas twice and it started. I had them sort out my Demon reciently, very happy w/results.
If you have to pass smog, get a pro built q jet. JMHO

Ricisan

 

The most common causes of "Quadrabog" are:

1) Mal-functioning accelerator pump. To check, take the air cleaner lid off and look down the primary (small) barrels. As you look, pull the throttle linkage. You should see two strong, squirt gun like streams of gas shoot into the barrels. If the streams are weak, sputtering or non-existant, your pump needs repair. It is easy to fix, but if the carb has never been rebuilt, you might as well get the kit (which contains the pump plunger) and go through the entire carb.

2) Mal-adjusted secondary air valve (air valve is the butterfly over the secondaries). To adjust, find the small flat head adjusting screw on the passenger side end of the air valve shaft and the allen head screw coming up underneth it at 90 degrees (use a mirror to find the allen head screw). Loosen the allen head screw to allow the flat head srew to turn, then loosen the flat head screw until you see the spring on the airvalve shaft (use the mirror) loose contact with its tang, then re-tighten it 7/8 turn past the point at which the spring contacts the tang.

Between these two, you will probably find the fix. The second one is free and easy to fix. the first one is still not too bad to take care of. Bad news is, I would guess, if the pump plunger was the original that came on the car, the ethanol in the fuels these days did it in. The good news is, you can get plungers for the pumps now that are not damaged by ethanol.

God bless, Sensei

 

Great info, guys! Once the new gas tank is installed and get some fuel moving through the lines again the carb is next on the big list.

 

Most common problem with the quadrajet is the secondary fuel tubes. There are 4 tubes in the top cover. 2 tubes are the fuel pickup tubes and 2 are the secondary booster tubes. These have a bad habit of falling out of the cover.
The secondary air valve spring a1sensei mentioned is only for closing the air valves. As he said it must be adjusted correctly. The spring does not control the opening rate. That is controlled by the choke pull-off. If the pull-off is bad you will have a secondary bog.
Mike