Messed with my carb, now exhaust backfire

[hollowch]

My exhaust will now backfire when I get up to a high RPM and let off the gas with it still in gear. As it winds down, I get a ton of backfire. Also after I shut it down, the engine self ignites and revolves/chugs a little before it stops (not sure if related?)

How do I fix this? I'm a newbie at carbs btw.

 

[BUCKNBRONK]

what carb is it? what did u do to it?

 

[hollowch]

what carb is it? what did u do to it?

The stock carb on a 302. I rebuilt it with a kit from Autozone. Much needed btw.

 

[BUCKNBRONK]

Did u get the vac line hooked back up to the dissy? check for cracks, u either have too much fuel (missed something in the rebuild) or the vac advance is not working. With it dieseling I would check the dissy hook ups.

 

[bad 68]

if the carb is the only thing that you messed with between it running ok and running like crap, It's most likely the carb rebuild. Most rebuild kits come with parts that cover many models and years. Probably got a wrong part in it.

Did you check and adjust the float level to begin with??

 

[hollowch]

if the carb is the only thing that you messed with between it running ok and running like crap, It's most likely the carb rebuild. Most rebuild kits come with parts that cover many models and years. Probably got a wrong part in it.

Did you check and adjust the float level to begin with??

Yeah I was pretty meticulous about replacing the right parts in the reassembly. I had all the old parts on hand to match them up just to make sure. And yes, I measured the float in accordance to the instructions.

 

[J-man]

Hey mine just started doing this too. I have a Holley 600. Now that I think of it my buddy adjusted the screws on it and it now back fires the same as yours. I may try changing those screws bake to stock

 

[hollowch]

Hey mine just started doing this too. I have a Holley 600. Now that I think of it my buddy adjusted the screws on it and it now back fires the same as yours. I may try changing those screws bake to stock

Any idea what the stock screw settings are? And yes I did mess with the fuel mixture screws

 

[J-man]

I think my buddy opened the screws 1/2 turn when I get home tonight I'll run them all the way in and let you know.

 

[hollowch]

I think my buddy opened the screws 1/2 turn when I get home tonight I'll run them all the way in and let you know.

shit, mine are out 4 1/2 right now

 

[dave67fd]

Typically with Holleys and other's
With engine off turn both screws in till they bottom and then back them out 1 1/4" turns.
Start vehicle, and let it warm up.
Connect a vacuum gauge to an full time vacuum source (intake manifold).
The carburetor throttle plate is just fine. (Very bottom part of the carb)
With the vehicle running, (and in gear with an automatic) Turn the idle mixture screws on the metering block clockwise the same amount until you get your highest vacuum reading.
Start with about 1/4 turn at time, and KEEP BOTH SIDES THE SAME!
If, on rare occasion, the vacuum reading goes down when the screws go in, turn them out 1/4 turn at a time until the highest vacuum reading is achieved. Re-set the curb idle speed when you are done with the idle mixture.

 

[Bundy]

Mine did that too and it was running too rich- leaned it out and now it runs great. I just drove around with a screw driver adjusted the screws 1/4 turn at a time until it stopped but what Dave67fd just said sounds easier and more accurate!

 

[broncnaz]

Your carb rebuild kit should have gave you baseline settings for the idle mixture screws usually 2 turns from fully seated. As was mentioned final adjustements are made with the engine fully warmed up. vacuum gauge is good to have but not really needed. adjust each screw until your find the highest smoothest RPM. As you adjust you should find that the engine will speed up/slow down and miss you just find the spot where it runs the smoothest and your good.