I do not have ether one yet, just wondering out loud:

What is the best range of operation of each?

Does changing the Offy carb mounting to the 4BBL make it into a hot street setup? Such as a 2bbl for daily driving, and swapped to the 4bbl for the occasional trip to the drag strip?

and out of curiosity, what RPM range does the Hyper-Pack like the best?

I have the Offy with a 500cfm Holley 4412 on a stock engine with -.090" cut from the head. It runs great but the power band isn't much different than it was with the stock 1V set up. The Offy runners looks to be the same size as the stock intake, it's just lighter and gives you the 4V option.

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Years ago I took a micrometer to the ends of the runners on a Super Six intake and an Offy intake. I don't recall the exact dimensions, but the differences were negligible, like on the order of thousandths of an inch. The Offy has the benefits of being aluminium, having a proper four barrel carb opening, and mating to the factory exhuast manifold.

These days, I like the Offy because it is easier to machine and weld aluminium than cast iron. Good condition stock two barrel carbs are getting hard to find, but you can buy new four barrel carbs that are sized appropriately for a slant six or can be modified (i.e. lock out the secondaries) to work with even a stock slant six.

So I guess what I am saying is, "Yeah, what drgonzo said."

Correct. The Offy gives you a wider range of carb choices depending on the adaptor plate combination used.



This will depend on the intent:

Clifford Hyperpak will come on about 3500-4000 and depending on build will start to fall off about 5500 rpm...
Clifford Hyperpak with a divider welded into the plenum (split 1-2-3 from 4-5-6 )...increases mid range power down to 32-3500 rpm depending on build will pull to 5500-6000 (had wound mine to 6200
for launch...manual transmission)
Dutra Fat Pak 4 barrel comes on about 3500 and goes to 6000.... typical engine build to support it will be very high compression, large cam, not really a street runner for low rpm use...

Thank you for your responses.

New questions, coming from a place of interest, curiosity, and maybe bench racing...

1)Does the Offy with a 4BBL actually expand the RPM range over one with a 2BBL?

That is to say for instance: IF a 2bbl Offy work from idle to 4000, and the 4bbl version stretch the power band to 4800?


2) is there a "better" street manifold, for mid range RPM? say 1000-4500?

Oh and a new question:

3) Would welding a divider into the Offy produce similar results to welding a divider into the Clifford Hyperpack?

This is more of a function of the volume of air the carburator can process, and also your camshaft's ability to
allow a cylinder to get that much air (porting/valve size/etc.. helps here too depending on what engine is built for).

I could never get the BBD to make anything over 5K on the clock...Holley 2300 had no problem even on stock valves
revving to 6K...but thestock cam would eel over well before that.




This depends on the build... if it's close to stockish (RV-10 cam) then Offy would work fine... if you are going OS valves, porting, 10:1+ on compression and headers...then
the clifford would breathe better (but not the best winter driver, FYI).



No. The reason on the hyperpack is because the plenum and runners are much bigger than the short ram manifolds in volume, so it helps reduce what each cylinder sees
in volume per cycle. The other reason is runner length... the addition of the divider changes the characterstics of the manifold so that the "wave" that pulses along in the
sweet spot of the Hpak while ram tuning now changes things where the ram tuning occurs a bit lower in the rpm band...short runners are better for broadband rpm usage
vs. the more specialized long ram manifolds.

That being said... the split plenum will allow you to isolate the inline 6 into "banks" like a V engine... if you have split exhaust headers or manifolds... this will allow a carburator
to be specifically tailored/tuned to each "bank" (1-2-3, and 4-5-6)... but there would not be any advantage to doing it performance wise.

If you are interested in some of the theory on manifolds, I would recommend David Vizards Making Horsepower Vol.2...

I will get the book and do some reading. Thanks for the recommendation.

I can tell you from personal experience on my old Duster, switching from a BBD/Super Six to an Offy and 390 Holley was worth over .7 tenths in the quarter.

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How much motor was underneath that super six? I am imagining (and wanting to believe) it was more on side of optimized stock-ish instead of being a race motor that was suddenly uncorked by a new intake and carb?