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By easyissy - 15 Years Ago
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I am running the Ford 2x4 intake with dual Edelbrock 500cfm carbs on my 1958 Ford Custom 300 with a 292ci engine. If anyone has run this set-up which rods and jets did you use? The engine runs but when I stop on a hill or have a heavy load it dies. Am I running a bit too lean? I figured someone must have run this set-up at one time or another and had it dialed in. I've tried adjusting the A/F mixture and also changed out the step-up springs with no luck. My next project would be to change out the rods or jet combination. Also, when the car is put in drive the idle drop considerably but I checked for leaks and found nothing. Could this also be a symptom of running lean? PLEASE HELP!
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By Vic Correnti - 15 Years Ago
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I have a pair of 1405 Edelbrocks on a Edelbrock 255 manifold. I bought the carbs two years ago and have the rods and jets that came with them as follows, .100 primary .095 secondary with metering rod .070 x .047. The fuel mixture seems fine and I have had no issues other then it sneezes every now and then. The carbs that these replaced were Carter 500's that I used for over 30 years and per my notes they had .092 primary .084 secondary and .059 rods. My notes didn't have the larger size for the rods just .059. I would guess that they were around .070 -.075. Are both your carbs linked together? I use a progressive linkage and only one carb is in use until around 3500 RPM. It sounds to me you have a vacuum leak some where with the idle dropping off when put it into gear.
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By easyissy - 15 Years Ago
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I am also running a progressive linkage. Originally I did have a vacumm leak where the manifold met the heads because of a broken intake bolt. I replaced all the bolts and reintalled the intake. I did the vacumm leak test and it seemed to be fine but when I drop it into drive it still drops considerably. I installed the carbs straight-outta-the-box so I figured my next thing would be to check the rods and jets. I've also tried to change the step-up spring to the stiffer spring but it did not fix the problem completely. It stays on now but idles very low. According to Edelbrock the stock specs are: .086" Primary & .095 Secondaries with .065x.052 rods The specs you provided would make it run more rich which will probably solve my problem. Would I change the rods and jets on both carbs? Thanks for the info.
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By Ted - 15 Years Ago
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Have you performed a vacuum check on the engine when it’s in gear? Depending upon the camshaft that’s being used, you may need lighter power valve springs in each carb due to the vacuum signal to each carb being cut in half when using carbs in pairs. Some more initial igition timing advance may also help depending upon where the timing is currently set. If you cannot kill the engine by turning the idle mixture screws in on the carbs, then you’ll have to address that; possible causes for this include retarded ignition timing, vacuum leak, wrong carbs for the application, or unsynchronized carbs among other things. Are the carbs idling equally or is one of them treated as a primary carb and the other as a secondary carb. If idling equally, then the idle mixture screws should be set the same for both carbs as well as both carbs having exactly the same throttle blade openings at idle. If you’re treating one of the carbs as a primary carb, then the secondary carb should be set at almost dead closed with only anough idle speed screw adjustment to keep the throttle blades from sticking closed. In this scenario, the carb that has the primary throttle blades closest to the center of the engine will be the primary carb. If the carbs are facing forward (most common setup), then the rear carb would be the primary carb. Backwards facing carbs would have the front carb being the primary carb. On a primary and secondary carb scenario, staged or progressive linkage should be used so that both carbs reach full throttle at the same time while allowing 1/3 or more throttle opening on the primary carb before the secondary carb starts to open. You're essentially doing your cruising on the primary carb with progressive linkage being used.
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By easyissy - 15 Years Ago
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Thanks Ted for the suggestions. I have not checked the vacuum yet. I'll run down to harbor freight to pick up a vacuum tester and check the vacuum when I drop it into gear. Should it be at a certain measurment? As for the carbs I do have them set-up in a progressive set-up and I am using the rear carb as the primary with both carbs facing forward. For the power springs, according to the edelbrock manual they suggested I go stiffer but what your saying makes more sense due to multiple carbs = divided vacuum. I'll try the lighter springs once I get a vacuum reading. Thanks again.
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By slumlord444 - 15 Years Ago
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If you are running the Ford intake manifold, it is designed to utilize the idle circuits of both carbs. One carb feeds 4 cyllinders and the other carb feeds the other 4 cyllinders. It will not work as a progressive setup using only the idle circuits on one carb. The idle screws must be screwed in much further than on a single 4 setup because of this. This would cause the type of problems you are having. Try it and see what happens. You may still have to play with jetting and power valves to get optimum performance and driveablilty with this set up. It did not make a lot of sense to me when I first set up my dual quads in 1965 but that is the way it is designed to work with the Ford factory manifold.
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By easyissy - 15 Years Ago
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I did a vacuum check and at idle it jumps around at about 12-15" of vacuum then when I put it in drive it drops down to 5". Is this a problem? I've checked for leaks with no success. I'll try and run them together rather than progressive and see if that helps. Thanks for the suggestion.
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By charliemccraney - 15 Years Ago
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Don't know much about multi-carb setups, I'll be corrected if I'm wrong. I think it should have more vacuum than that, and it should be relatively steady. Check for vacuum leaks, check timing, check valve adjustment. Try adjusting the idle mixture screws for the highest vacuum reading. If everything else is functioning properly, the idle screws will alter the vacuum.
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By easyissy - 15 Years Ago
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I've set the timing to 8 degrees but I'm not sure about valve adjustment. If I disconnect the distributor vacuum advance it does'nt shut off on me when I'm on a hill or heavy load so I guess the vacuum advance canister has to be adjsuted. As far as I know the cam in the engine is stock. It runs now without shutting off if I disconnect the vacuum advance but the power is still weak when pulling away from a complete stop.
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By ecode ragtop - 15 Years Ago
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JUST MY HUMBLE OPINION,AND I AM RUNNING A COUPLE OF MY CARS WITH DUAL QUADS, I THINK 1000 C.F.M. IS TO MUCH FOR A SMALL CUBIC INCH MOTOR WITH A STOCK CAM. TOM
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By yalincoln - 15 Years Ago
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are you using the right vacumm port for the dist. ? NO vacumm at idle on a ford.
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By easyissy - 15 Years Ago
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I'm using the vacuum port above the thottle blades.
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By easyissy - 15 Years Ago
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Just an update on my dual quad set-up. I took slumlords advice and ran them inline instead of progressive which helped greatly. I also set the timing and a/f mixture with a vacuum gauge to achieve the highest vacuum. I also swithed out the points with the Accel points eliminator kit. Now my vacuum is pretty steady at around 15" at idle. When I tried to check the timing with the timing light I didn't see any marks so I think the balancer slipped greatly over the years. I just lefted the vacuum advance disconnected and she SCREEEAAAAMS now, even chirps when that Fordo kicks in . Thanks to all for the great advice.
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