if you know anything about q-jets...look

[gold84gmc]

i have an 84 gmc 3/4ton with a 350 and a q-jet.....i am having problems. i rebuilt it a couple months ago, because if i pushed the gas to much it would surge(like its not getting enough fuel) and i changed the float because it was plastic and it had a hole in it....so i put a bronze one in it. but after getting the carb back together and on it still did the surging...i was thinking that i didnt adjust the float right

[VileZambonie]

Explain in more detail your "surging" Are you sure it's not an ignition system miss?

[HAULIN IT]

Yes, Please explain a little more. The word "surge" to me means: At a steady speed the engine speeds up momentarily & then returns to the previous RPM. What exactly does it mean to you? I would personally not feel that the word surge applies "when you give it the gas". I agree with Vile, many surges are ignition related. Lorne   

[Blue 82]

Check your fuel pressure first

[gold84gmc]

well when im going up hills i cant push the gas anymore than maybe 1/4 of the way then it starts to surge(RPM's go up and down, and cant gain any speed, i had to go less than 5mph up a hill cause of that)it acts like the fuel pump puts in enough gas then it uses it then puts more gas in and so on

Check your fuel pressure first

how do u check the fuel pressure?

[Blue 82]

Buy one of these at your local auto parts store

[VileZambonie]

Recheck your float level.

[ccz145a]

While your at it, check that the vent tube is not blocked.

[gold84gmc]

what do u mean by vent tube...where is it and what does it look like

[ccz145a]

Can't find a good pic. It opens the bowls to the atmosphere, they will be within the air horn area.

[Blue 82]

Over the years, several different floats were used on the Q-Jets. These floats had different geometry with differing float arm lengths and different float lengths. Some floats can be interchanged, but this will result in binding, sticking and improper needle control. I also see a lot of aftermarket brass floats used in Q-Jets. The original carbs came from the factory with NitroFill floats. Brass floats do not behave the same. Be sure to install a correct NitroFill float when you work on these carbs. Echlin makes an exact reproduction and correct replacement float.



Incorrectly Set Power Piston Stop Height
Results in: Poor idle, rich idle, ineffective idle mixture screws, hesitations and stumbles.
Comments: Post-’75 Q-Jets have an easily adjustable power piston stop that determines the lowest (leanest) position of the piston. Raising or lowering this stop outside its limits will adversely affect all performance parameters of the power enrichment circuit.


Here's the power piston adjustment location

[Blue 82]

here's some info here:

http://www.digitalcorvettes.com/forums/showthread.php?t=88376

[JJSZABO]

here's some info here:

http://www.digitalcorvettes.com/forums/showthread.php?t=88376

Very impressive Blue - Good job!

[Blue 82]

I think JET uses a screw at adjust the power piston,
SMI drills, then taps this location and installs a pipe type plug for access to the power piston. I have this feature on the SMI Q-Jet that I installed a few weeks ago, but I have not had time to play with it (yet). According to SMI it can be adjusted while running.

[VileZambonie]

What did you mean the air cleaner hits the float? 

The power piston usually isn't an issue unless you have really wild cam and aren't producing a ton of vacuum which you can also compensate for with a lighter spring.