When Ford had the factory dual quad in 1957 it was straight ahead with chokes on both carbs. I would think that only running a single carb in a dual quad setup would lead to fuel distribution issues causing the longer runs to be lean. Oldmics
Whats up D! Is it a single or dual plane manifold? You will only need a choke for very cold starts, Id run straight not progressive linkage, if you do go progress you'll only need a choke on the primary carb if its solid linked you have to choke both....... And is electronic choke really an option? Also 1000cfm seems like a lot if you didnt bump up the compression
Depends on the intake as much as anything else. Are your carbs on a common planum or are they on separate plenums. If your plenums are separate then you have no other choice then to run them on straight linkage, if they share a plenum then you can run progressive. If progressive is an option then I would suggest progressive. I have run them with choke and choke delete. The difference is that choke delete you need to get some heat into your engine and intake prior to driving it. I think that you should warm one anyway so it is not a problem for me. If I were running a choke progressive I would only see a need to choke the primary carb if I was running them linked and choked one I would choke both. Now to kill a minor misconception, on a car with an intake with a plenum the runners do not get fuel from the carb. The intake should be full of a fog or a mist of fuel and air mix, when running down the highway or down the street the cylinders be pulling the fuel/air mixture and once the plenum is full as long as the engine is running the mist should remain. One will note that I often tell people to not undercarb their tunnel ram manifolds for example. You need you carb/s to be large enough to keep the plenum full of air. A carb is rated @ a specific CFM. That is a rating based on how many cubic feet per minute of air that the carb will flow not how much fuel it will flow. The same applies to any intake manifold, you have to keep your plenuim full. If you keep your plenum full it is not as important where the carb is located.
Look at an early Corvette intake. The 283 had two 435 or 465 carbs, (it was a long time ago) the rear had a choke and was a primary, but the idle screws were open on the front carb too. When the rear carb was just short of half way open, the front started to open and they both reached full open at the same time.
You can run either progressive or direct, it has been made to work both ways. I would take the chokes off because it cleans the sides of the carbs up some. If your carbs have vacuum secondary’s I would not worry about over carbing it as the secondary’s will only open with engine demand. If they are mechanical and you think they are over carbed just unhook the secondary’s.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o> <o></o> FWIW I ran a pair of mechanical 600 CFM Edelbrocks on a stock SBC. I ran progressive with the rear carb doing the idling. I still had to crack the front carb's idle jets open. I pulled the plugs every 100 miles for the first 1000 and never saw any noticeable difference between any of the cylinders. To get engine happy under hard acceleration I ended up unhooking the front carbs secondary as 2 600's on a stock SBC were just too much carb.<o></o>
FWIW, I always run my 2x4s straight synchronized. Progressive linkage is way more trouble than it's worth. Looking at it another way, definitely leave the secondaries progressive as they are designed and air flow operated, so unlike double-pumper Holleys, your Carter/Edelbrock carbs will never open to full 1000 CFM, because your 360" can't **** anywhere near that much air - self regulating. No worries. jack vines
I run two Carter Compe***ion Series 500 CFM on my 455 Olds on an Offenhauser Dual plane 360 intake I have run them both ways and in my application I prefer the progressive style. When I ran the straight style linkage driveabilty was not as smooth and well mannered as the progressive. But as they say opinions are like a..holes everybody has one and they all stink!
It is a single plane with dividers. I would run them progressive, you will like it better. Oh and I doubt that you are going to do that but for everyone else; you cannot or should not run your carbs sidways on that particular intake because it is divided the way that it is. It is made so that the 4 left barrels run the left side of the engine and the four righ barrels run the right side of the engine and the holes in the dividers are ballancers the same as ballance tubes on a log type of manifold. If you cintact Weiand with the part number of the manifold they will give you recommended CFM for the intake.
We are just experimenting with this right now on the 455 Olds in my Son's rpu. He had tripower on it and wanted to see how 2 x 4's would look and perform, so he put on an Offy intake and two 600 cfm Edelbrocks. The setup came from Mondello. We just got it on and he has put about 200 miles on the new setup. We first went with progressive and it ran well there, nice and smooth and lots of power. Then we adjusted the Lokar linkage so both are opening at the same time and it runs just as smooth but power seems to be much better. The only adjusting we did on the carbs was to turn the idle screws in, they were at 2.25 turns out and we went in to 1.5 turns out. The power seems to be way up over the previous tripower setup and gas milage seems to be no worse or better. I also ran the same 600 cfm Edelbrock setup on the previous 302 in my 27 with straight linkage and it ran fine there for years. But when I built the new 331 stroker for it I went to a Lokar progressive linkage because my other Son Don is running his that way and I wanted to try it. It has been running pretty well on the progressive setup, so I have just left it that way. As for the electric choke vs manual, we all run manuals because we live in Florida and really don't need a choke, plus we don't like seeing those black round deals on the sides of the carbs. We just wire the chokes on both carbs open all the time. Don
if you can set up the front barrels on both carbs to open at the same time and then the rear barrels to open under power ,i say doit this way,otherwise the one carb will feed the closest runners and lean the rest.carb signal is based on alot oth things other than just manifold design.what type of cam are you running?close c/l or wide?for a street engine you typically dont want all 8 barrels opening at same time ,but if the carbs are sized correctly just about any thing can be made to work.
"Progressive vs solid linkage" is almost like "Carter vs Holley". As mentioned by others in this thread, either can be made to work. In our shop, unless we are doing a full restoration on a factory progressive system, we will use solid linkage ONLY on dual quads. If the customer demands progressive, we politely refer he/she elsewhere. CFM is NOT an additive property when used in a multiple configuration. Two 500's probably would come out to be about 750 total. Two 400 CFM (Carter numbers 9400s or 9410s) should have tremendous throttle response on the street, and maybe lose a few HP at WOT if dynoed. Two 500 CFM (Carter numbers 9501s or 9511s OR 4758s) would produce slightly less driveability, but a few HP more at WOT. The 9501s and 9511s both have electric chokes. The 4758s has a manual choke. If you are bound and determined to use progressive, Carter offered the 4761s as a chokeless (normally front) companion to the 4758s. The 9400s and 9410s may be mixed or matched on the same setup (difference is an EGR port which may be plugged). The 9501s and 9511s may be mixed or matched on the same setup (difference is an EGR port which may be plugged). Do not mix a 4758s with anything other than a 4761s (see above). We have two Carter 625 CFM running solid linkage on our shop 390. Don't see how it could be any better. Jon.
Dave, yeah, I remember you were one of the guys Dan chatted with a lot when he was building his car. He is fine, still building his OT Mustang, and working days and playing in the band at night, so he isn't around much. He's also been racking up the miles on his rpu. The breathers are Moon, same ones I am running on my 331 Ford, except his are on a different angle. I needed them because my Ford has no way to add oil and the removable top does that for me. He liked mine and added them to his engine. Don
Yes, but please take no offense that I am not going to try to type it all in on this forum. There are many issues involved, not the least of which would be the size of the engine on which the carburetors are placed. Maybe a better term would be "effective CFM". Here is an article that you may find interesting: http://www.thecarburetorshop.com/Carbshop_carbsizesandCFM.htm CFM in general is a cl***ic example of the old saw: "Figures don't lie, but liars figure"! And most of the Carter numbers I mentioned are available. Jon.
Only a problem if you are running one of the automatice transmissions with a TV cable. The added travel in the pedal will cause the TV cabel to be extended further out and increase transmission pressure/harder shift. My 2x4 offy on the 409 with 700r4 will bang shift all the gears with progressive linkage even when cruising because of the added pedal travel to go a given speed. I find it easier to tune with the 1:1 linkage. Front barrels of the rear carb are near enough to the center of the 360 type intake to work well either way on a stick shift car.
very impressive info from knowledgeable people------i always run progressive and have always liked it...i am ***uming this car will see plenty of street time
I dont understand having a dual four setup only to be hell bent on running around on two barrels with progressive linkage. I liken it to having all the performance parts, then crying about gas mileage.
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