Some information from you guys who use, or have used the Buick 455 Offy 2x4 square bore manifold, please. Here’s what I “know”: 1 - A single plane 4-bbl manifold will produce more power. 2 - A dual plane 4-bbl manifold will be more responsive on the street. 3 - A 2x4 set-up produces a greater “Wow!” factor (very important for a strip/street rod). 4 - Dual AFB/Edelbrock carbs are the most popular for this manifold. 5 - Dual Holley #4160 carbs (secondary metering plate, vac. secondaries, single feed) in line will barely fit [according to a trial fit I did with some old cores (specific part numbers unknown) and some photos I took at the Nationals a few years ago], although the bowl fastener heads of one carb may contact those of the other. 6 - Dual Road Demon Jr. carbs in line will just barely fit (according to Barry Grant literature). 7 - I think the Holleys or Road Demon Jr’s will produce more power than the “AFB”s. 8 - I think that shiney-finish or chrome Holley's or Road Demon Jr's look better. Here’s what I would like to know: 1 - What model/brand carbs are you using? 2 - What size? 3 - Straight linkage or progressive linkage (especially for street use)? 4 - Approximate HP or torque of your engine combo. Thanks in advance for your help.
I was running two holley 4412's. I wish I hadn't sold it. It run alot better than the set-up I have know.
My favorite is to use the 2X4 linkage from the 427 Ford camp. You mount Holley carbs backward on the intake (primaries facing the firewall). The factory linkage is very adjustable and is progressive in operation. A bellcrank mounts between the carbs with the attaching point for the throttle linkage reversed back to the drivers side. I had no clearance problems at all with factory Holley carburetors, but I have no idea about the Demon and others. A good starting point would be the 600 cfm versions, like an 1850 if you can get them. Ford used the 600s to start off and went up to twin 780s later on ,,,,,,,, vacuum secondary for both with a balance line between the two secondary units. I paid $125 for factory linkage back in '77 or so. Now there are repos out if you decide to go that way.
Thanks for the responses, leo455 and GM Muscle (Terry). Everyone else, please keep those cards and letters coming in. I need all the info I can get. I looks like I'm going to have to spend some time on the Holley website deciphering their model numbers (i.e., 4412, etc.) Terry: That Ford linkage set-up sounds pretty trick. Thanks. One questiion, though: How is the linkage rod that runs from the passenger side bell crank routed over to the driver's side? Since the carb float bowls all but touch each other, I would guess the rod must be located between the top of the bowls and the air cleaner(s), or between the bottom of the bowls and the manifold??? Judging from what Ford did with carb sizes, I'm thinking that I may have to use 750 cfm carbs. With the fairly large primaries on the 750's, progressive linkage will almost be a necessity for good street "drivability". I'm thinking that I can get away with the less cumbersome straight linkage if I used twin 600's. By the way, I'll be purchasing Holley's shiny-finish, chrome or chrome/powdercoat-finish "universal" carbs (if I go Holley, that is), since they're readily available from places like Summit, or Holley "Custom Shop". Since I'm looking for those models with custom finishes, however, I suspect the price will go way up and availability (at discount prices) will go down. Anyway, thanks again.
I wish I could remember exactly what I used back in the eighties on my motor for the linkage. I think it was something I made up with threaded rod. But I had 2 Preditors sitting atop of my Offy dual intake. I was running a KB cam, I think it was a mark103, but had 540 lift and 320 duration both intake and exaust. I will say that the Preditors was a wicked setup. I was also running the Mr. Gasket street scoop that was at perfect levelness to the hood. Here is a good pic from the old days shortly after sitting the motor in. I may not have helped much, but figured I would pipe in with my experience. Mike
Hi Dan. The crossover bolts to the carburetor mounting studs and is very compact. There are only two other bacic linkage pieces. If you look at a 1850 Holley, that is the style of carb linkage this was designed to work with. I wanted to try a pair of NOS 660 center squirters, but someone offered me enough $$$ to let them go. I will see if I can find you some pics.
As you can see, this is very simple and effective. The slotted piece is the progressive travel for the primary carb.
I sorry I didn't say that 4412 are 500 cfm 2-barrels. That's right 2-barrells . These carbs are used by dirt trackers and these flowed 580 each. I used the higher end Mr Gasket linkage which was my down fall.
I am having Charlie Evans build my iron stage 2 headed engine with the 2x4 offy intake. We are going to use 2 Holley 660 center squirter carbs,that will bolt on okay.We are going to run a solid linkage,so all of them open at the same time. We will have a street,pumpgas engine,with a hyd cam. We haven't picked a cam yet,as he has to flow the heads and work on the intake.I do know several people running this intake,that have made it work,with alittle help. Mike Nussell :3gears:
I ran the Offy dual quad setup on my 462" BBB powered 32 roadster for quite a while. It had a Kenne-Bell #118 cam among other things. Carburetors are Carter Competition 500's - same as the Edelbrock #1404's. It was a good responding setup that got reasonable mileage all things considered. Linkage is straight, non-progressive, made from Bearing House Heim's and 1/4" stainless throttle rod. At the time I ran dual mechanical chokes operating from a single cable, but have found since then that choking the rear carb only works fine. What I really liked about the dual quads was the smooth tip-in on the secondaries. They seemed to overlap a bit instead of both popping open at once. No flat spots. Jetting remained stock and the only change was pulling the black metering rod spring and installing a pink one so as to get away from the low vacuum caused by the cam pulling the rods open at idle and low rpms. It helped that I lived at 350' altitude. A few years back I went to a milder cam and an Edelbrock Performer intake with 750 competition Carter with electric choke kit added. Now it runs an electric choke 750 Edelbrock. The Edelbrock cuz it was brand new and way less than half price in the speed shops used parts box and I didn't want to disturb the good running Carter. (Plus, now I have a pair of 750's for the dual quad setup if desired.) I still have the dual quad setup and big cam and it's on an up and coming project. No doubt the carbs will require some jetting changes since I now live at 3400' altitude. The single 750 got leaned out a touch and it's running pretty good, so no changes there. The pic shows the easy to build linkage, home-made air cleaners, fuel log etc.
Thanks again... Thanks again, everyone. Those photos made your descriptions much easier to understand (especially Terry's set-up). From the looks of your responses, my options are wide open. There seems to be no single "best way" to set up a 2X4 system. The choice of a linkage set-up confused me the most. I figured that straight linkage would be hard to syncronize and would cause a lot of off idle hesitation on the street (because of the size of the four primary barrels combined). On the other hand, I suspected that there would be mixture distribution problems at off-idle and cruise conditions with progressive linkage. It sound like, from your responses, neither condition was an issue. Thanks again. If someone else has any inputs, don't hesitate to jump in. I'm all ears.
In using the 4412's the straight hook up was my only choice. I worked with the 2-2 barrells, because 4 barrells were easirer than 8. When I get another offy I will use the same carbs,spacers ,but I will get areal linkage set-up.
I use two road demon jrs 625's rear carb is primary, progressive linkage I made from rod and heims I have a 212s cam stg 1 headers etc 373 gears 26" tires and get a consistent 11.7 mpg very streetable after I blocked idle and power valve circuits on front carb. response is great! my car only weighs 3100lbs and I have a 4spd so it may be a little more forgiving I will try and attatch a pic walt ps out of box and no tuning on wheel dyno went 574 tq and 331 hp
Hey Dan, If you aren't in a big rush, I am putting together another 2X4 setup using the Holley carbs. When it is done, I can get you some pics. Another feature of the 427 linkage is that you can adjust it for 'all at once' too ,,,,, very versatile.
Terry & Walt, Thanks for the info. No big rush regarding info on your new set-up, Terry. I'd like to see, hear about it when you're done, though.
