Buick Rodders, I purchased a complete 2x4 intake with carbs and linkage for my 401, but it was completly dissasembled. I was wondering which carburetor was the primary unit. Do both carbs work at idle and then the progressive linkage kicks in the second carb? I have worked with six packs before and have always worked off the middle carb. But in this situation, it seems to be a little un-balanced. By looking at it, I think the back carb with its primarys and dash pot location is the feed at idle and crusing. The back carbs primarys seem to be the most centrally located and the dash pot stop hits the throttle just right on decel. If it where the front carb, I would think that the back cylinders would be starved out to the point of lean miss and the dash pot would be a waste. Please give your thoughts on this Doug :3gears:
Doug, Look at my post on parts sources in the nailhead section (sorry I don't know how to do a link). There are pictures of a couple of 2X4 setups. Good luck,
It's progressive.......first the rear carb primaries open, then the front carb primaries, then the secondaries of both begin to open simultaniously until you can't push the pedal any further down.........by now you're doing 90! :laugh: At idle the front carb is completely closed. If you have the correct rear carb, the idle speed is set by an air bleed screw as opposed to an idle stop screw as on the single 4 barrel. The accelerator pump on the front carb must be set to the center or outer hole, as the plunger spring acts as a throttle return spring for the front carb only. If you put the rod into the closest hole, the plates will not close all the way at idle all the time, causing an erratic idle speed. :bglasses:
any1 have any sound bits of their dual quad nailhead dipping into the secondaries or at WOT? ive never even heard what a built nailhead sounds like let alone a 2x4 and im curious cause im building one myself.
Damian, I do not have a sound clip but, If you would have been in the stands at the BPG Nats when they gave out the car show awards I had the air cleaner lid removed and did a full throttle run after receiving my plaque. It sounded great echoing off the grand stands.
man i wish i coulda heard that, my wagon isnt the closest in the world to being done and its driving me crazy but i know that in time it will be and when its done all my waiting and saving and work will be worth it. do you think you can load the soundbit of it on the site? i really want to get an idea of what my car may sound like when its done.
2x4's Doug, you are correct... the rear carb is the primary carb. If the setup has the correct carbs, you will see one carb has idle enrichment screws and an air bleed screw of the front near the base-this is your rear/primary carb. It is also the only one with a choke valve and thermostat. (the pictures from Greg's manual are incorrect with the front carb showing the choke also but the linkage and stuff looks right.) The front carb should have no adjustment screws in the front, just plugs to block the holes. This carb acts as a "dumper" such that is works like the secondaries on any other carb. It has no idle circuit, fuel only gets drawn through by engine vacuum after the butterflies start to open.(aside from the shot of fuel the accelerator pump gives when opening.) The system works well such as a tri-power in that only two barrels are open in crusing mode but all open when tromped on. The sound is a bit different than a tri-power because both carbs have vacuum secondaries which usually open slightly later than the front butterflies. They sound cool, run well if tuned right, and pull like crazy on the high end.
jaredyocum Hi guys I had a dualquad set up on my 65GS for many years and loved it the AFB carbs tended to loose accellerator pump seal after setting for a while but when fresh worked great! I hope to get mine going again soon I do remember the sound of My 401 through a set of glasspacks at full throttle and them quad sounded like they were gona suck a dent in the hood! Goodluck! After all if it aint got loud pipes and use allot of gas I just ain't much in to it! Jared
Yes, there's an air valve down inside the secondaries......it's hard to see but it's in there. :bglasses:
I don't know how to do sound bites...........but maybe come spring I could tape my cell phone under the hood and do a full throttle run so you can hear it! LOL :3gears: I'm just bored, nevermind me. :laugh:
Joe I like the cell phone idea. My Riv wont be comming out of the garage till spring either. I was thinking that with the progressive linkage arrangement they were mechanical. but using my fingers for primary throttle blades I see how they would work with vacuum secondaries. See my fingers are more than just for counting :laugh:
cool idea with the cell phone, i bet itll sound evil, man i cant wait till i scrounge up enough money to get more stuff done for my nailhead i still have to get my rods done and then get my pistons made and then i gotta get my carbs and my cam, etc alot left to worry about. Building an expensive motor on a shoestring budget lol. whenever i can ill get my pictures loaded on a disc and post them on the boards here.
Video tape I have a short video tape of my supercharged dual quad 425 nailhead being broke in, in my garage on a stand. Open headers with flames and all. Disturbing the peace. Still not the same as being there, it's the best I can do. I see you are in Riverside, I'm in Murrieta, give me a call and you can see it and make a copy if you want. Don 951 677-6706 Disturbing the peace. :laugh:
oh thats awesome must be an evil motor, yea i think id like a copy of that itll hold me off till mines done accept for the fact mines not blown, lol. :3gears: :beer
Video tape into internet I will see if I can find someone to convert this into a media player format. It is so coooool I get goose bumps every time I watch it. Nailhead junky or what. :beer
