[FJ4ZROX]

I am looking at changing the primary jets in my Edlebrock Q-jet. This is due to obvious carbon build up in the tail pipe. The carb I have (Edelbrock #1904) came with .073 jets - what do you guys/gals recommend for a mildly built/balanced Chevy 350? I am thinking of trying .068 to see if it cleans up the exhaust any (might eliminate the slight backfire I have developed when letting off the throttle).

 

[steveh]

You may want to make the decision based on how the plugs look, not the tailpipe.

 

[FattyCBR]

Actually if there's carbon/soot buildup in the pipes that the same as black plugs (rich). Same indicator, different method.

Milan

 

[COMPLAINE]

The backfire sound like a small exhaust leak is letting air in and it burning with the unburnt fuel. The only way to fix that is to eliminate the leak, because you can never get rid un burnt fuel with a carbuerated motor. But i would agree that the motor is running too rich, and a smaller carb would a good idea.
Have you thought about propane? It shoud be a realy easy thing to do in your area. Clean burning, runs at all angles, no carbon in motor, and CHEAPER.

Ian-

 

[Aggro]

AND don't forget the roughly 30% power loss associated with propane over gasoline.

 

[COMPLAINE]

Originally posted by Aggro:
<STRONG>AND don't forget the roughly 30% power loss associated with propane over gasoline.</STRONG>

If it is tuned well than it is only like 10%. And it is not noticable wheeling.

 

[pmaddy]

If you really want to get it dialed in, I would buy the jet kit they sell. It is pretty pricey (100 bones) but it comes with an assortment of jets, metering rods and accelerator pump parts. The chances of you guessing exactly what jetting will be perfect is prett slim. Lots of trial and error and you will eventually get it dialed in. It is best to take small steps and keep track of the results. I believe the .068 would not be too drastic of a jump. Though if you go to lean you will have overheating problems so keep an eye on your plugs and temp guage. Quadrajets take some serious pacience becasue swapping the jets is not as quick as most. I probably tore mine apart 5-6 times before it was perfect. Once you get where you want it there is no better set up. They are reliable and the best carb in the rocks. There is another adjustment on that carb called the ATP or something like that. It controls how deep your meter rods sit in your main jets when you are at cruising RPM's. It is located under a silver plug on the front top of the carb. If you loosen it out, it raises the meter rods location at crusing RPM's (richens the mixture). If you screw it in it lowers the rods depth at crusing RPM's (leaner). When you take the top off the carb to put in your new jets, pop the silver plug out so you can mess with this adjustment after you are finished.
Hope this helps.
Later

 

[NE-RokToy]

where can you get jes for a quad? I know if I went to the local parts store and asked they wouldnt know what the hell I was talking about <IMG SRC="smilies/smile.gif" border="0">

 

[Arnold]

I'm pretty sure http://www.summitracing.com has 'em.