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Ford Hoarder
78 & 92
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8,273 Posts
Wide Band o2 sensor will tell you exactly what is going on. However that is likely the same $$ as a different carb.

I do feel like yes you'd likely give up a bit on the top side but the 2150 will likely run better down low, tho I don't think a 600 Holley is too large either. Just sounds like it has the wrong combo of jets and such in it. I would also look everything over really well for a vacuum leak, and make sure the distributor is doing what you think it is both mechanically and with the vacuum hooked up (if you run it down the road that way). You may look into getting the duraspark distributor re-curved too.
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Ford Hoarder
78 & 92
Joined
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8,273 Posts
@schwim It sounds like to me (from reading on here on this post) you are right in that spot where it is switching between what feeds the fuel inside the carb. Meaning stuck between the idle and the main feed or in a weird place where the secondary is just starting to open or something like that. On some carbs you can tune this out, but then you might have an issue if you down shifted and floored it. Very hard for me to get feel for what should be next step without seeing/hearing it run in person (me personally I am sure maybe some other board members can help more that know the Holley's well, I'm more of a Demon guy). Is why I suggested wide band O2...

When I spoke to top end I was meaning 3500/4000+ rpm if not higher is where you likely will see some drop off in performance. Sounds like you may not care if you don't drive it there.... In contrasting example the carb 460 that was in my 78 (before went 429 with Sniper), was never below 3k rpm so the idle to 3k rpm transition was critical to me. Enough so that it likely would not run super great at the rpm's you usually drive (Just different end goals is all)

CFM = (Displacement * Max RPM) / 3456

ie: (400 x 5500) / 3456 = ~650 cfm

General rule of thumb / use for reference only above... Rather applied to your situation (400x3400) / 3456 = 393 cfm....
 
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