Jims50chrysler Posted July 10, 2009 Report Posted July 10, 2009 Ok I have rebuilt 1 carb for my dual carb set-up and put it on my car still with the stock single carb intake and it runs fine. I adjusted the idle then the mixture screws untill the engine ran smooth. I am about to attack the second carb but before I do is there anything else I can do to make sure both these carbs will be similar when they have to work together on the dual carb set-up? suggestions? ideas? thanks Jim Quote
greg g Posted July 10, 2009 Report Posted July 10, 2009 You will need to synchronize them to make sure the throttle plates open at the same time and the same distance. There is a synch tool that was common to motorcycles and British cars with dual or triple side drafts. It like that thing they give you in the hospital after anestesia to ger your lungs going. It has a little red puck the gets pulled up a graduated tube by the air flow. Match the flow, and yer good to go. Quote
Jims50chrysler Posted July 10, 2009 Author Report Posted July 10, 2009 will this work http://www.zivney.net/library/carbsync.pdf I am guessing it gets hooked into the vac advance port? Jim Quote
bkahler Posted July 10, 2009 Report Posted July 10, 2009 will this work http://www.zivney.net/library/carbsync.pdfI am guessing it gets hooked into the vac advance port? Jim Jim, thats one way to do it but that way is pretty involved. This is what I use on my Triumph sports cars: http://www.minimania.com/web/Item/uni-syn/invDetail.cfm Works great. All you do is set it on top of one carburetor and take a reading and then move it to the other carburetor and take a reading. They should match. If not you make the appropriate adjustment to one of the carburetors and check again. Continue until they match. Also make sure when you're at wide open throttle that both throttle plates are in the same position. Same for idle speed settings. During idle speed testing you want the linkage between the two carburetors to be disconnected so they can move independently. Brad Brad Quote
Don Coatney Posted July 10, 2009 Report Posted July 10, 2009 This tool is used for linkage adjustments only. With this tool you set both throttle butterfly plates so they pass the same ammount of air at idle. This is done by adjusting the linkage. This tool will not work for fuel mixture adjustments. You can see from these two pictures what an out of balance setup looks like. Quote
bkahler Posted July 10, 2009 Report Posted July 10, 2009 Nice pictures Don. Sorry I forgot to mention that mixture adjustment is done just as you would for a single carb however the linkage has to be disconnected between the two carburetors so you can monitor the changes as they are being made. On twin SU carburetors as used on Triumphs mixture adjustment is very easy. Since I haven't as yet tuned a B&B carburetor for mixture I can't say if its easy or not. Hopefully someone else can comment on that issue. Brad Quote
James_Douglas Posted July 10, 2009 Report Posted July 10, 2009 One thing to keep in mind is that with two carbs the venturi area has gone up. With the venturi area up the vacuum signal past the jet ports (idle, intermediate, and main) will go down. Due to this, it is often necessary to increase the jet size to achieve the same fuel flow on a twin 1BBL set up. Also ethanol has less BTU than gasoline and if your area has 10% ethanol or more in the gas, you may need to increase jet size by 5% for that. Just check (read) the spark plugs and keep an eye on the temperature gauge for any indication of lean running at part throttle and idle. Best, James Quote
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