Holley cfm selection

[hysteric]

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[hysteric]

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Apologies hysteric, I have just edited my above post for clearer explanation while you were replying to it.

Definitely not enough difference in the test carbies to spend the coin changing out carbs. But useful info if you were in the market for a new one.

Just read through the entire article again. A little bit of credibility lost when they say they are going up in size from the 830 to 950.

I agree that atomization and therefore vaporization is easier with smaller venturi carburetors, yet larger and assumed lesser atomization and vaporization are making more power. Are there modern booster designs out there other than the large annular that atomize better allowing for increased cfm?

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From Vizard





Fig. 6.15. Dyno tests support my “think bigger” philosophy when using a flow-efficient, dual–plane intake. The relatively basic 383 test engine has a set of Gil Mink–ported World Products Sportsman iron heads with a 10.5:1 CR. The cam is one of my hot street-spec hydraulic flat-tappet grinds. As you can see, it produces 536 hp and that’s pretty respectable output for an engine like this. Most engines with this sort of spec don’t make that high an output with a single-plane race-style intake.

The point, however, is that if the typically recommended 750 carb had been used, the output peaks would have been 476 ft-lbs of torque and 511 hp. Although that’s hardly an output that anyone would complain about, it is not the 487 ft-lbs and 536 hp seen with the big carb. A couple of points to note to validate the results here are that the intake had no plenum cutout and the torque curves of all three carbs were virtually identical up to 4,000 rpm.

The blanket statement made on review of these results is throttle response would suffer without any supporting data other than hypothesis.

Back to my original question: how do you hone in on cfm for your combo?

[hysteric]

Have you seen the price of HP's lately? That was an expensive test if they didn't get the carbs for free or heavily discounted.

Not sure on the boosters but a stepped downleg may be the way to go for more flow and decent atomization. You could try using smaller diameter boosters on a bigger venturi to pick up some of the the signal you lose but I have never done it to really know. I picked up a Holley 650 HP main body when they were cheap to try so I might get the chance before I go back to the TQ's Not sure there's much you can do with a Holley to get better atomization as opposed to other designs

[hysteric]

What happens before 4000 RPM though?

[hysteric]

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