changeing jets on a carb

[joeydeherrera54]

i have an 83 gmc with an edelbrock 650 and i am going to change the jet to a smaller size i bought a kit and i was wondering what size should i go on the jets and also the metering rods and springs

[436'd skylark]

before I could help I would need to know more about the motor. be very specific. what makes you want to change the jets?

[joeydeherrera54]

i have a 383 well i was told it was a but i think its a 350 but anyways i want to change the jets because its running rich and thats what i was told to do i know the floats or anything like that are getting stuck because my friend just bought a new carb for his car same kind i have and it still was running rich

[75K30]

Altitude, compression, timing, and a veriety of things need to be addressed before you start changing jets and metering rods. For example: which circuit is running rich? IS it just rich ad idle, and the adjusting screws are not effective? Does it blow black smoke under WOT runs? Temps rather low? IS it rich when the engine is hot? Is the choke functioning?
Knowing all of the circuits, and what they are responsible for is the first step. You can turn a small problem into a large one if you can't identify exactly where the problem is. Just knowing that it is "rich" is too vauge, and might send you trying to fix or change something that does not need to be touched.
For example, if the slow air speed circuit is not clean, and the carb is dirty, the signal for slow speed is lost, and the carb will indicate a "rich" idle condition. Changing the metering rods will not fix this, and actually cause a bigger problem. This condition will stumble during acceleration, and may leann pop as it transitiond to and from the intermediate circuit. Many guys in this situation will change all of the jets trying to repair the pop and stumble, and give too great a shot of accelerator pump squirt, and lean out the main circuit, and, yep, problem gets far worse than when you started. Tis is a common example that many tuners overlook.
Troubleshoot, and pinpoint where the problem is, and start with the easiest component to test. Verify that you have a clean functional carb before you start changing parts, and document everything that you do. Worst case, is that during your changes, you can always go back to where you started if you write stuff down. Guarantee you will forget what you originally had, and you will be up a creek. Use your current set-up as a baseline, so if things start to not run right, you can always go back to your baseline set-up.
Good luck. Carbs can be fun, but can also be a nightmare if you do not completely understand thier functions.

[o3shortbed]

Originally Posted by 75K30

Altitude, compression, timing, and a veriety of things need to be addressed before you start changing jets and metering rods. For example: which circuit is running rich? IS it just rich ad idle, and the adjusting screws are not effective? Does it blow black smoke under WOT runs? Temps rather low? IS it rich when the engine is hot? Is the choke functioning?
Knowing all of the circuits, and what they are responsible for is the first step. You can turn a small problem into a large one if you can't identify exactly where the problem is. Just knowing that it is "rich" is too vauge, and might send you trying to fix or change something that does not need to be touched.
For example, if the slow air speed circuit is not clean, and the carb is dirty, the signal for slow speed is lost, and the carb will indicate a "rich" idle condition. Changing the metering rods will not fix this, and actually cause a bigger problem. This condition will stumble during acceleration, and may leann pop as it transitiond to and from the intermediate circuit. Many guys in this situation will change all of the jets trying to repair the pop and stumble, and give too great a shot of accelerator pump squirt, and lean out the main circuit, and, yep, problem gets far worse than when you started. Tis is a common example that many tuners overlook.
Troubleshoot, and pinpoint where the problem is, and start with the easiest component to test. Verify that you have a clean functional carb before you start changing parts, and document everything that you do. Worst case, is that during your changes, you can always go back to where you started if you write stuff down. Guarantee you will forget what you originally had, and you will be up a creek. Use your current set-up as a baseline, so if things start to not run right, you can always go back to your baseline set-up.
Good luck. Carbs can be fun, but can also be a nightmare if you do not completely understand thier functions.

yep hes right. carbs can be very tricky especily if the carb is used when you get it.

[joeydeherrera54]

ok sorry it took so long for me to update but i have tried ajusting it that helped a little but still it runs rich i cleaned it out with carb cleaner and it runs rich from idle to wot it does smoke when at wot and the choke is working i checked that to