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I recently switched over to a 4160 Holley (600 cfm) that I had on my shelf onto my 318 with 8:5:1 compression, hooker headers, 3 angle valve job to heads, Comp XE268 cam, 2500 TC, and 3.23 gears. I had an Eddie 600 cfm on it before. The low end on the Holley is fairly good, but it seems that when floored, there is a tad less grunt above 3000 rpm and it feels like the revs waver slightly, like it may be lean. It doesnt pull quite as hard as it did when opening up the secondaries on the freeway at 70 mph. This carb has the secondary plate in the rear and 72 jets in the primaries. Is there a way to richen the carb up on the top end a bit with converting to a 4150 style setup with actual metering blocks and jets for the secondaries?

You would likely be best off by optimizing your Holley Tune-Up rather than attempt to add a secondary metering block. If you get the Tune-Up correct, it should work fine. Lots of parts are available to custom tune a Holley.

Yes, you could experiment with just adding the metering-block and longer-bowl-screws, plus a plug for the Power-Valve opening, but I believe it's not as simple as it may seem.

Certainly, if trying to fully convert to a 4150, though it's possible to do, there is more to the conversion than it's worth.

To do that, you would need to drill holes in the main-body and modify it quite a bit to put a secondary accelerator pump squirter, bowl w/ pump, secondary-shaft FOR accelerator-pump cam, pump-lever, etc, etc, plus secondary mechanical-linkage.... and after all that, it may not work right.

So, it is really not a worthwhile way to go about it.

Better to sell the 4160 and buy a 4150; Or, go to Holley.Com and/or buy a good Holley book and learn more about Tune-Up and upgrade parts selection.

Or, take it to a Carb shop that specializes in custom-tuning.

Here is a Link to Holley.Com:

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