Can anyone tell me how to tune my dual carb setup. They are sitting on a 383 chevy with 64cc Edelbrock heads, flat top pistons, and a modest cam. I'm trying to figure out if I need to jet them down or what?
You might need to synch them up. I'm not a carb pro by any means. More info might help too. What size jets? Are they 2 or 4 bbl? Was it running good on one alone? Is your timing right? What is it doing that you think it is over jetted?
Oh I'd say 3 carbs is going to give you more fits than 2. Carb tuning is a dance not a karate chop but you need to have the correct units for the application.
They are the stock 500 cfm carbs. The car runs good but idles really rich. It also hates to start when its cold too. I was running a 650 CFM but had to jet it up and change the metering rods.
Are you running a choke ? That helps with cold starts. Idle circuit controls your mixture at idle, that's the screws. It's not needed but if you are rookie a wide band sensor and gauge will advance you quickly.
I'm running two 600's on a 331 Ford and just took them out of the box and bolted them on. Plugs burn light tan, idles well, etc. Are you using progressive linkage ? What rpms are you idling at ? Edelbrocks are a little under tuned for smooth street use, so I can't see the jets being your problem. Don
If they are of the AFB family make sure that your idle stop is not set up to far or you wont get any idle mixture control.
Vacuum secondaries can be a problem with dual 4 bbls. But I hate Edelbrocks anyway so what do I know. BUCKD
I prefer a single carb for the simple reason of tuning...since I don't have the proper tools for tuning double or triple carbs.
I am running two 500s on my Son's truck with 350 and a mild cam. Our carbs are the ones specifically for the dual setup and were calibrated out of the box to get us close. We are also using the progressive linkage. It idles from both carbs so I set all four idle mixture screws at 3/4 turns to start and then adjusted them to achieve the highest idle and then setting the idle speed using the main idle screw. We drove it to the round up from Houston with no troubles and the plugs looked great when we got home. What specific problems are you having with them? Posted using the Full Custom H.A.M.B. App!
Sure does!, especially if he's listening to, and help the knowledgeable dyno operator tune/adjust his carbs & ignition. If he lived down the street from me, I'd be happy to help him. It'd be cheaper and quicker going to a qualified chassis dyno/tuner, than chasing the 100's of opinions, he's gonna get hear. If you want to so it yourself, get a "How to Carter AFB Book, and an A/F meter and get to work. The fact that it is hard starting, would have me looking at the ignition first, more ignition problems are blamed on the carb/carbs than you can shake a stick at!
Let me start by saying that I am not a big fan of the Eddy carbs. But I know of a lot of fellas that have had very good luck with them, even a guy that has held the yayhoo cup record and done it on a 2500 mile round trip. That said bigfoot has let us in on a very important aspect of your question. What is the problem with the 2x4 setup? It is running fat or stumbles or??????? Give us information like CFM ratings, what the plugs look like, etc. Are you running them straight up or progressive? They no doubt can be tunned and are a very dependable carb for the most part.
I ran 3x2's on my 46 for about 12 years and currently have a set on my T. If you set them up with the correct end carbs and run progressive linkage, they are great. If you try to go cheap and use regular carbs for the ends, they can be a bear to tune. It helps to keep the fuel pressure down to about 5 PSI, too. Three small rochester 2G's are only going to give you about 600 CFM or so. Perfect for an engine in the 327-350 CI range. BTW - Just responding to the poll, can't help you with the 2X4's.
Only problem I see with a tri power setup is that if he can't tune two carbs he damned sure can't tune 3.
I'm not a Edelbrock fan either, but I disagree with the vacuum secondary statement! Vacuum secondary carbs are a plus with dual carb setups, especially if you link the vacuum signals so they open together. Vacuum secondary carbs wont ever open before the engine calls for more, so they work much better in a dual carb setup than mechanical secondary carbs.
Lighter step up spring under the needles will allow the adjustment screws to have an affect on the idle A/F ratio. They are color coded and sold at Jegs and the like. Try one lighter and see if the screws have some adjustment.
Soon after I got my dual 650 AFB's going it started running rich. Problem was one float a had crack and flooded, replaced it running great ever since. Either progressive or direct. Did opt for a dyno A/F checked out fine. <input id="mac_address" value="" type="hidden"><input id="mac_address" value="" type="hidden"><input id="mac_address" value="" type="hidden">
He has the setup now he needs to get it adjusted no need to throw more money at it by changing it again. Paying a pro to set it up if he is willing to teach you is the most efficient way to do it. None of us sitting behind our computers have any idea what' s actually going on with it.
That's the best part about tri power, all you have to tune is the primary. On a "correct" tri-power set-up the end carbs should not have idle circuits in them. You run off the center and bring in the ends as you see fit with progressive linkage. I've been running tri-power on all but one of my cars since 1966 and never had a problem as long as I used the right end carbs. That said, I think if he has a dual quad set-up he should tune it, rather than switching and spending more money.
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