Seems like a really easy question, but I haven't found the answer on YouTube or online parts house. I have the Holley 4BBL 390 CFM carb.

When I pulled the bowel off the secondary sidea, I see a plate held in with a bunch of screws (Allen wrench head?). There's a 58 stamped in the plate. My guess is that's the jet size.

Where do I find the jetsigned? Is it the big plate? On the backside. My 58 is smaller than others.

Thanks!

The 58 refers to the size of the main metering holes in the metering plate. There are also two idle circuit metering holes in the plate. Either of these holes are variable, depending on the plate used, i.e., a 50 mmj plate could have various holes.

Usually 4Vs are jetted a little lean on the primary side for economy and emissions and the secondaries are jetted a little rich to make up for the slight primary side leanness at WOT.

Why do you want to change the secondary side metering plate?

Hi Flyer,

Thanks for the info. I've now found the metering plates for sale. Odd name, though.

I'm learning, not planning to make any changes. Car is still running lean off the line, but better with the 9.5 power valve.

There's a place in town that will dyno the car, put on the O2 sensor, and determine what needs to be changed and then make the change. I get a nice chart when done. I'll probably go the route, but may fiddle a little bit more with bigger jets and power valve before I take it in.

But more than everything, I want to be prepared if they propose changing the metering plate.

Thanks!

Good luck, let us know what you learn on the dyno.

I love dyno tests.

If you do plan on changing or at least tuning the secondary, you may look into upgrading to a secondary metering block kit. There aren't as many plates as there are jets sizes for sure. Plus I've had a secondary plate warp on me and cause all kinds of problems.