holly double pumper

[86c20]

ok i have a 454 with a holly on it and had it rebuilt but now i need to tune it in as its runnig way to rich. what way do i turn the air bleeds? i have set the floats altho they maybe a little low. is there anything else i should do? thanks, mike

[Weasel Diesel]

Just so we know what we're working with... which holley, 650-750??

[86c20]

i think its a 650. theres no cam or anything like that. but what would be the diff in tuning for them?

[raceman6135]

1. Verify float levels - both primary and secondary

2. Adjust idle speed. This is adjusted via a screw on the throttle lever, driver's side.

3. Adjust the idle mixture screws. For most Holley carburetors, there is one screw on each side of the carburetor, located in the metering block, approximately half way up the carburetor. Use a vacuum gauge connected to full manifold vacuum and adjust each idle screw until you achieve the highest possible vacuum.

4. You will likely have to go back and forth from driver's side to passenger's side idle mixture screws in order to get them set properly. As a reference, most Holley carburetors' "starting point" for the idle mixture screws is one-and-a-half turns out from LIGHTLY seated.

5. You may also have to decrease the idle speed as you hone in on the proper idle mixture adjustments. If the idle speed is too high, the carburetor may not be pulling fuel from just the idle circuits, and any further adjustments to the idle mixture screws will be erroneous.

6. Most Holley carburetors do not have adjustable idle air bleed screws. Holley generally reserves this feature for their race carburetors, and if you are running a race carburetor on a street or street/strip engine, you will go insane trying to get it lean enough throughout the RPM range to give decent mileage and performance.

7. Also verify the fuel pressure as close to the carburetor as possible. Most Holley carburetors will become problematic if more than approximately 7 PSI is forced to it.

8. There are further adjustments to the main jets and accelerator pump circuits which can be done, but that would take up another dozen points.

9. The carburetor spends a surprising amount of time on the idle circuit in the majority of street driving, so making sure the idle circuit is properly tuned will go a long way to solving most suspected carburetor problems.

10. Don't disregard the condition and settings of the rest of the engine. Primary and secondary ignition systems must be in good shape, spark plug gaps adjusted properly, vacuum/initial/mechanical advance settings of the distributor confirmed, general condition of the engine such as ring and valve seal, PCV system, no intake manifold leaks, and valve adjustments.

11. If everything else checks out and you do need to adjust idle air bleed screws, you can either remove them from the carburetor and drill them larger to lean the mixture, or purchase the proper size ones from Holley or a speed shop. If your carburetor has non-adjustable idle air bleed screws, your only option is to drill out the brass bushings, and if you go too large, you will need to pull them out and purchase or fabricate new ones and press them in.

Hope that helps!

['82 steppin]

Search in youtube for holley tune and you will find what you want
Posted via Mobile Device

[86c20]

thanks guys that will get me going anyway. now i just need the good weather to go do it lol