Packard Forum Index » V-8 (1955-56)

FWIW, the accepted formula says a 352" Packard can only ingest 366 CFM @ 4500 RPMs. Any carb larger than a 500 CFM will never fully open the secondaries. A 650 - 800 CFM effectively becomes an oversized 2-bbl.

thnx, jack vines

Interesting, since the Caribbean used dual carbs that had to be at least 400 cfm each. Must have just put the extra carb on for show then?

The formula says a 374" needs only 415 CFM @ 4800 RPMs. Packard did claim 20 more horsepower on the 374" Caribbean. Here are Packard's advertised horsepower figures:

374? w/1-4bbl - 290 HP @ 4500 - 400 lbs/ft torque @ 2900
374" w/2-4bbl - 310 hp @ 4800 - 405 lbs/ft torque @ 3000

My guess would be if in fact there were twenty more horsepower, it comes from the 2-4bbl intake being more efficient, not from the extra CFM. It would be interesting to put one on a dyno and see if the secondaries open and if so, how much. In theory the four primaries could supply sufficient air.

Very few stock Packard V8s will even turn 4800 RPMs. The valve springs were not up to controlling the long, heavy intake valves. The 352"s in many overdrive '56 Golden Hawks died trying. All three of the stick shifts I have pulled down showed evidence of dropped valves.

I just bought a 1956 Motor Trend with road test comparisons of the '56 Corvette, the '56 Thunderbird and the '56 GH. They made much of the Corvette 2-4bbl 265" having far too much carburetion for street driving. On that little 265", GM put two of the same Carter WCFBs used on the 352" Packard. The Golden Hawk was much quicker and faster than the Corvette and the Thunderbird.

thnx, jack vines

Thanks for the reply Jack, I've always wondered about that too. It seemed to me that a dual carb setup on the Carib was a little too much anyway. My bet is that since the carbs are mechanical secondary, they open whether the engine needs it or not.

All this is the reason why I'm using dual 1.25" S.U. carbs on the twin turbo 327. Going with dual 4 bbls would be wayy too much, but I still want the better fuel distribution that dual carbs give you, especially on a 40" long engine.

There is a formula for calculating HP to the REAR WHEELS based on a test run of the car. I can't find it yet.

I've often wondered about the dual quad and big cfm carbs being too much several times.


If one weree to come up with a way to mount a modern video camera to the side of a WCFB with a remote on/off button then during a test run the opening of the secondary counter weight could be witnessed.

A Q+D way mite be to mount a toothpick in some dumdum next to the WCFB secondary counter weight and see how much it moves after a test run. I mite try it.

Hey everyone, thanks for the great response, sorry I didn't post back sooner. My phone broke and it's the only source of Internet I've got at the moment.

As far as the what carb I'm receiving is, as I was told sound more like the edlebrock 600cfm mentioned above. The original post I made was based off of what I was told by the guy I'm getting it from. And as far as I know it's barely used.

I'm pretty sure anything I throw on there will be better than the Rochester currently on it. Considering it's not the original carb to my car. I made the mistake of selling that one when I was younger. And the one on it was an eBay carb that I'm also improperly rebuilt. And again when I rebuilt it due to lack of tools. I can't get ahold of the guy right now but when I do I'll try and post a part number for it.

Is the original air cleaner going to fit under the hood if I use a spacer?
And am I better off with a spacer than boring the manifold?

IIRC the Rochesters used on the dual quad setup on the 56 Caribbean have a second set of throttle valves (air-flow induced) mounted above the mechanically operated set of secondaries? There are many other differences between the 55 and 56 dual quad Rochesters, but this may be the most signiificant. Anyone out there explain what problem they were supposed to cure?

Here's what Packard said they were for.

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