Idle mixture screws

[Josh]

I have a Holley 850 DP that has idle mixture screws on both sides of the primary metering block, and no screws at all on the secondary block. Is there a good reason there are no screws for the secondaries?

[TT302Z28]

It is likely that this is an older carb that pre dates the 4 corner idle circuits.

These carbs likely were also before power valve blow out protection.

With that said, these carbs were just fine. Google the numbers on the air horn and you'll find the date produced. I wouldn't hesitate to run it.