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Location: Perth Australia
|Let me save your pain (or join in it) |
I believe you have the same problem I have
Mine is a fully rebuilt 318, pistons are 40 up on stock, so the engines actually a bit bigger, I had a cam ground specifically for the 2x4 setup (cant remember the numbers, but its not "lumpy"), I also am running electronic ignition, advanced until its just under pinging
It has 2x 500 edelbrocks (brand new), 1 with an electric choke, 1 manual thats wired open (only need to choke 1 carb) and the throttle is set to operate both carbs the same
I have not messed around with the jetting yet, but I have tried staged linking the carbs, I have shifted the accelerator pump linkage in both carbs through all 3 holes a couple of times, tried without the air cleaner and have improved it, but not cured it by a long way, but one thing that did make a big difference was adjusting the kickdown.
Mine loves revs, once its up there, it goes fine, its just crap off the line and I am actually putting it down to loss of vacuum, but I have not tested that yet (havnt got around to it) but try putting a vacuum gauge in the car and go out and test it.
I cant offer much more than that, but I am watching
|You have to first ensure the carb jets are the same size and then calibrate the carbs by vacuum demand vs fuel demand, both carbs should read the same[balanced] assuming the carb linkages are set properly.If your running an automatic you may have reduce the torque convertor pressure to achieve vacuum vs fuel demands. Check out YOUTUBE for vacuum/fuel calibration you may find it useful. You may be experiencing some fuel supply pressure drop. Anyway that's my 2 bits worth of info I like I always say "If I can't explain the subject matter well enough for Gramma to understand then I don't know the subject"|
Location: Colorado Springs, Colorado
|2x4's are tough, look for a local shop with a dyno and an anaylizer and come with a nice assortment of Jets/rods for the carbs. You need to spend some serious time tuning those carbs in. You would need to do this even with the plymouth carbs. I'm going to be doing the same on my 392 even with a single carb. There is no magic bullet to fix your issue, just tuning that needs to be done.|
|I'm very interested in this topic as I intend to set up my old 354 hemi with the Dual 4bbls using the original LOG intake set up I've was fortunate enough to get my hands. So much good info shared here and in my research has found similar advantages/disadvantages to dual carb set ups.I'm using 2/4bbl original WCFB 2314's I'm leaving the old Hemi as is [stock] so I was wondering what problems the Dual 4bbl setup would cause. First was matching up the carbs I had one and fortunate to find number 2. I'm assuming that 58ply you have done you're homework too. somethings I found so far were 1} factory spec timing is just that your engine is a [ 1 of ] so assuming the cam you put in according the marks on the gears are lined up correctly on install 2) TDC marks were checked to be correct [ Remove the # 1 spark plug and place a dial indicator in the cylinder in indicate the piston at TDC by turning the engine over of coarse,now check the timing marks [piston should be at maximum height in cylinder] you may find that you have 4-6 or > degrees manual advance that can be used. Now readjust your distributor vacuum advance settings if you haven't done this already. 2) Ensure your coil is providing full power at max RPM. 3) Check the operating carbs now using your vac gauge If this indicates some discrepancies you have to balance the carbs first. Now assuming this is all correct and the problem still persists You to have establish proper intake pressures vs exhaust pressures. The cam has changed the operation of your engine. Your valve dwell and overlap and valve size are in play here. Scavenging in the cylinder occurs and are asset for higher performance up to a certain point[valve overlap] then it becomes a disadvantage as in retards the ignition in the cylinder after that. Assuming that's correct. Direct your attention to your exhaust this has to meet the demands of your engine, the back pressure may be to high or not heated enough[ tune exhaust practises] can be a crap shoot. All the information shared by the other members here should have given you improved performance. One question is this an automatic or a standard tranny behind this 318, the automatic also influences vacuum demand the same as your power brake booster would. I'm learning from others experience so as stated here I'm assuming that everything I've mentioned has been done. I get the same feeling from setting on a warm toilet seat LOL I keep reading here for follow up results Thanks Guys. Last minute research from the manual. |
CARTER WCFB CARBURETOR
GENERAL DESCRIPTION AND OPERATION
The Carter carburetors used on engines with dual four barrel carburetors
differ from those used on single four barrel carburetor
equipped engines. An additional set of throttle valves is incorpo -
rated in the secondary bores of each carburetor to give better
performance at lower speeds. Also, a new form of idle adjustment
Is made through the use of an idle by- pass screw which replaces
the idle speed screw.
Edited by RUSTORICHES 2017-01-20 6:34 PM
Location: Tampa, Florida
|Back in the dark ages (1976), I drove my Fury (318) 2 X 4 carbs from Tampa to Tulsa for the NSRA "Street Machine Nationals". |
I rebuilt the carbs before going and I experienced similar problems to yours.
After narrowing the problem to the rear carburetor ( original WCFB), I found that the "T" shaped piece of metal that the metering rods hang on, was slightly bowed. It would stick and the metering rods would not function properly.
I straightened it and the car ran fine after that. (My hiway mileage improved from 9 mpg to 11 mpg also)
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