[Hal Copple]

I'll offer my experience with the Holley's, as i have run all three.

My Windsor is stroked to 396 ci. Performer RPM intake manifold.

first carb was the silver finish 4160, had a metering plate rather than a rear metering block. You adjust the secondary "jetting" by getting different metering plates. Userful choke, etc. But under a very short (because of hood clearance) air filter, so the air down into the primary (choke) side has to make a very abrupt downward turn into the carb. Remember, at full throttle the primary side has to suck as much air as the secondary side.

Swapped in a rear metering block, cost about $45 or so, then i could more easily change jetting. But makes the carb about 1/2 inch longer, so needed new fuel lines.

Put in a 50 cc squirter, replacing the 30 cc one, but then you can only use one of the several "cams" for the squirter.

Then cut off the choke tower, to allow more air flow down into the carb. This was several hours to do right. With straight leg boosters, if you cut too much off or try to match the sculpting of the Pro, the "boosters" are a bit high to properly meter the air, which now can come around the booster, instead of vertically past it. Be careful about this with the standard straight boosters.

Then swapped out for a vacuum secondary Holley 750 HP Pro. It is very pretty, with no choke of course, and very sculped air inlets, with down leg boosters. Bob Olthoff recommended a vac secondary carb for street use, avoids some bog on throttle tip-in.

Here is what i have learned and experienced. Bought four or five Holley books, so that eventually i became comfortable with a pretty extensive Holley tear down, and learned theory of what does what on these carbs. My car ran best at low rpm street driving, with a four hole 1/2 inch phenolic spacer (for reducing carb heat with winter gas, and fuel percolation on a hot-soak re-start). An open spacer caused some hesitation on throttle-tip-in, as the RPM manifold has a separated plenum, completely separating the two cylinder heads induction. I put in road race floats.

Found that tiny adjustments in the spring loaded squirter adjustment made for big changes in low rpm part throttle tip-in, more is not necessarily better, i had flawless low rpm drivability with less rather than more squirt, i think because my car is much lighter than the usual Mustang or Camaro.

Found i don't need a choke for my starting and initial running with out a choke on any of my carbs. You can see how you like no choke by simply unhooking (and taping) the choke wires in the winter for awhile. I can start it easily in temps down to freezing (i live in SC), and ease the rpm up, and drive right off, and within a mile, the exhaust heated intake plenum works to give good cold drivability. It was no loss to give up a choke for me.

I found the lightest spring in the vacuum secondary gave more than 40 # of torque and 40+ horsepower in the mid rpm range on a chassis dyno!!! Cheap for 7 bucks!!

It also showed no trace of power curve disruption on the dyno pull either.

Found the only change that seemed to increase the feeling of power was the change to the lightest spring, and when i put on the HP carb.

My speed shop pro, very helpful to me, (he is actually a big Demon fan) told me the power of the HP probably comes from the special metering blocks used, they are definately not the ones that come in the metering block kit for a 4160. He said it is metered "very aggressively". I found each change, for some reason, seemed to increase my cruise MPG. Go figure that one. Which is why justing putting the sculpted center you can buy for about $120 may not make much difference, as the power comes from the different metering blocks, more than the sculpting of the inlet.

He told me, and i have heard first hand from several others, that sometimes a Demon is fabulous, and sometimes no matter what you do, you can't get them to run just right.

Don't change too much with any new out of the box carb, there are hundreds of adjustments you can do to a Holley, i only changed jetting on my HP, and put in a different squirter nozzle, to give a longer/ less abrupt squirt for momentary enrichment on throttle tip in. I left the squirter cam and its setting stock, etc.

For use, i occasionally spray carb cleaner down the air bleeds and thottle plates, gas slowly gums things up, keep my linkage clean. Make sure your carb plates fully open up to verticle, and yet don't over-travel and bend something. Learn what your pedal does to your throttle plates. Have your linkage perfectly adjusted.

Here is what i have found. First, thoroughly learn what does what on your Holley, so you don't make things worse with tinkering. I have sure done that before i decided to learn carb theory.

A choke is not necessary for me at all. The more power my carb modifications gave, the better my highway cruise MPG was!

All my carbs gave absolutley perfect low rpm and drag race/road course drivabilty, with never any bog or lag. By "tuning" only the squirter spring, done by going out and driving with a screwdriver and wrench, and turning the setting in minuscule amounts, made all my carbs run pefectly.

Be sure you have adequate fuel delivery, big filter you change often (lots of debris gets into the fuel with the open LeMans type of cap when you flip it to refuel. A dampened fuel pressure gage is very useful in the cockpit to see what pressure you are running and if the fuel pump can keep up on a long pull. I run AN 8 lines off a 3/8 inch hard line, all gently curved AN fittings, so maximum fuel flow is available.

The Holley Pro gave a noticable "seat of the pants" increase in power.

When i was talking to my "drag consultant" about how my car seems to be making so much more power on a cold night, he said then i must be jetted too rich in the secondary side, so that the cooler, more dense air was a bit "leaned out" and i should drop my rear jetting a bit when it warms up next summer. I am intentionally rich with 80 secondary jetting, to avoid engine risk from detonation on the long long straight at full throttle at places like VIR.

But my best drag strip quarter mile, run on a cold night, with a prepared track, (ideal circumstances) was still with the original, unmodified carb under a small air filter!!!

In summary, you can indeed get fine drivability and excellent performance with any appropriate sized Holley, but for me, the power seems the best with a slightly tweaked HP 750 on my engine, on an RPM intake manifold.

Don't waste time spending a lot of time and money on trying to modify a 4160, use it right out of the box, or move up to a Pro Holley HP.

I can trundle along at 1000 rpm in fifth, and accelerate in fifth with no hesitation nor stumble. It can't get better than that.