Jet Sizes for Holley 390 Main and Secondary

[Rockonp04]

I am looking for recommendations for main/secondary jet size for my Holley 390. I've already changed my power valve to 4.5 and I ordered 56 jets for the time being because I think I am running lean. I put in a metering block and would like jet recommendations for the secondaries too. Any input would help.

 

[Barry]

You need to know what your air-fuel ratio is doing under various conditions before you start blindly changing the power valve and jets.

Either install wide-band O2 sensors in both collectors or have your car tested at a chassis dyno facility with the capability to monitor AFR.

 

[Rockonp04]

You need to KNOW what your air-fuel ratio is doing under various conditions before you start blindly changing the power valve and jets.

Either install wide-band O2 sensors in both collectors or have your car tested at a chassis dyno facility with the capability to monitor AFR.

Yea I understand the process but wanted to know what everyone else is running to give the tuner a good starting point.

 

[260Alpine]

56 is what the MG guys use in the GM 2.8-3.4 V6. Stock secondary metering plate jet equivalent is 58. The Holley needs more fuel pressure also. 5-6 psi. the 4 cylinder usually had 3-4 psi.

 

[Rockonp04]

56 is what the MG guys use in the GM 2.8-3.4 V6. Stock secondary metering plate jet equivalent is 58. The Holley needs more fuel pressure also. 5-6 psi. the 4 cylinder usually had 3-4 psi.

I've got 7 psi fuel pressure.