I'm looking for some help trying to figure out whether I can change my 1 x 4bbl setup for a 2 x 4bbl setup. The particulars: I have a 1962 Invicta with a Nailhead 445 (401 c.i.) with a single 4 bbl Carter carburator. I understand that for certain years (I believe 1964 - 1966), there was an option for a dual 4bbl setup. Again, I believe that option was only offered for the 425 c.i. Nailheads. I believe that the only real differences between the 425 c.i. Nailheads and my (401 c.i.) Nailhead were in the bore, cam, distributor, valve covers, air cleaner, and misc trim. If that is true, then theoretically I should be able to unbolt my current intake manifold and bolt on a manifold made for the 2 x 4bbl setup. Can anyone confirm for me whether this is true? I looked in the Hollander Interchange manuals, and they do not make any reference to this interchangeability. Next, I understand that the kickdown switch for the 2 x 4bbl setup is different than that for the 1 x 4bbl setup, as the transmission on these later models (TH400) is different than my (dynaflow) transmission). So, if I can't use the kickdown switch made for the 1 x 4bbl with the 2 x 4 bbl setup, but I can't use the kickdown switch made for the 2 x 4bbl setup with my transmission, what would I do? Also, as an aside, I don't even think I have a "kickdown switch" currently installed on my engine. Is this possible? What (negative) performance issues would I be experiencing if this switch was missing? Next, I've been told conflicting things regarding replacement of the distributor (were I to make this swap). On the one hand, I've been told: "get the GS distributor also or modify the original. The stock 401 distributor has 2 deg of initial advance and the GS has 12 deg. Youll need the initial advance out of the hole." On the other hand, I've been told: "Not true his distributor is 12 degrees if it's off a 62 401. The dynaflow engines to 63 had a 12 degree distributor." Finally, anyone have a sense for how much one ought to pay for a setup which includes: (i) the intake manifold; (ii) the 2 carbs; (iii) the linkages; and (iv) the kickdown switch (but no air filter)? Thanks in advance for any and all info. ATB Next, I guess I am questioning whether making this swap (if it is, in fact, possible) even makes sense. Is there any identifiable benefit to making this change other than a (relatively small) boost in HP (I believe an additional 20 HP).
2-fours The factory set-up will definitely fit your engine. The dynaflow does not need a kick down. Complete dual four set-ups are rare and EXPENSIVE ($1200 to $2000 plus). I bought a bare manifold recently off of E-Bay for about $300. However I am Going to use new edelbrock carbs. Carmen Faso's shop can modify your dist. He is listed in the supplier's sticky note on this board. In my opinion the single Q-jet set up (1966 only) is probably best for all around performance on a Nailhead (not near as expensive) but the dual four RULES in "sex-appeal"(appearance,rarity,sound,& top speed power). Just my Opinion! But Hey, do it Your Way!
I'm no expert, but if I remember correctly, the dual-quad GS-type 425 had a hotter cam than the single-carb motor. It strikes me that the cam would probably be as responsible for the power boost as the second carb was. Based on that, I should think that your smaller motor with a milder cam wouln't see that much of a power boost by merely switching to a dual-quad intake. I'm not saying there wouldn't be any gain, but it probably won't be all that dramatic. By the same token, you might lose some low end torque because you might lose some velocity on your intake flow. - Freed
I bought mine piece by piece,..this is what I spent: stock 2x4 manifold: $200 (2) after market carter afbs: $500 linkage:$100 after market fuel line with fittings:$160 reproduction kickdown bracket:$130 correct distributor:$140 (2)carb calibration kits:$100..(had to dial em in!) professional installation:$500
Your distributor is probably right because the 2x4 used a 12 degree which is the same as the one the dynaflowused. Can't help on the kickdown for a dynaflow but a stock kickdown anything will not work with a 2x4 set up. The mounting points are different. The rear carb is different for a 64 and the kickdown set up is different also. I have a 65/66 set up that would probably work on your car if interested. Intake, carbs, linkage, fuel rail. pm me if interested. Larry
