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Discussion Starter #1 (Edited)
I have a 69 Mustang with a 302 and 351 Cleveland heads. I have a Weiand high rise manifold with 2 Holley 660cfm carbs on it. The guy I bought it from did some bracket racing. We got the car running but it is running so rich that I start to choke after about 15 seconds. My question is: The guy I bought it from also gave me an adapter to put on the high rise manifold to go from 2 carbs to 1 carb. Can I put a Holley 750cfm double pumper on it ? I already looked into changing the manifold but that is tougher to find since it is modified and it has a different cam (size unknown). I think the 2 carbs was overkill. This is my first project car so any help would be appreciated.
 

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So basically what you have is a Boss 302..Yes you can certainly put a single carb on it or switch the intake completely to a boss or clevor intake..What do you plan on doing with the car?...Are you just going to street drive it or still race it?...What is the rest of the drivetrain(rear gears and trans type)?
 

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Discussion Starter #3
I am trying to detune it somewhat and make it streetable. Not a daily driver just something to play with on weekend. It had a spooled rear end and I changed that out to 3.0 gears with 28 spline axles. The tranny is an automatic with a 3500 stall that I plan open replacing with a stock or much lower stall.
 

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Here's another option just to try for laughs (it might actually work)! Assuming a max rpm of 6000 and a hi volumetric efficiency of 90% (that's getting into race car level), the max cfm flow I calc is 471 cfm (for a 4V carb). Now you have to remember in racing, if anybody is running inthe mid-range of the rpm band they need AAA- because they are lost and need directions (grin)-

If we assume for sake of argument that 500 - 600 cfm would work, divide that by 2 and that would be about 250-300 cfm per carb...now the engine really doesn't care if the carb is capable of flowing 200 or 1000 cfm...it just wants the fuel mix to be right....meaning reduce the fuel jets in each carb..the general formula for that is 50% of the cfm difference.....

Example.....if you had a 600 cfm carb with 71 jets and the engine only needed 500 cfm, thats about a 16% too much flow, 1/2 would be 8%, 8% of 71 is about 5, minus 5 is 66, so a #66 jet would be about right (within one step either way).

another and better option...

I had a friend who had a 350 chev with a duel carb highrise manifold....yup, too much carb, fuel, etc and shy on $. I convinved him to try (with adapters) 2 - 350 cfm holley 2V carbs (now 2V's are rated differerent than 4V's, meaning you have to multiply the cfm by 1.4 to evaluate the actually cfm flow in comparison to a 4V). That truck really, really ran good! Incredible torque at the low & mid-range, lost a little bit at 6000 rpm until redline (which was 6600), but it was a great daily driver and he actually got some decent mpg's out of it as well.....just might be a good least expensive option 9as compared to buying another manifold...BTW, for street use those 2 into 1 adapters typically , well, don't work well for low end drivability.
 

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I am trying to detune it somewhat and make it streetable. Not a daily driver just something to play with on weekend. It had a spooled rear end and I changed that out to 3.0 gears with 28 spline axles. The tranny is an automatic with a 3500 stall that I plan open replacing with a stock or much lower stall.
You'd probably be better off selling the engine and buying something else. Chances are, if it has a tunnel ram with dual quads it's also got 4V heads and a bit of compression with a big cam. It'll probably be a terrible street engine if you try and detune it and run a lower stall convertor. Sounds like the powertrain was built to run all out.
 

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Discussion Starter #7
The carbs are set up that all eight work together. So you either have nothing or all eight are open. The cars runs and for the first time I took a couple of laps around the neighborhood until it started running hot and I parked it back in the garage with the radiator whistling at me. I wanted to jump on it but I thought better not piss of my neighbors yet :)
 

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New guy here but I know a little about carbs. Those 660s are set up for race only. They run real rich anywhere but wide open. I would suggest a different set of carbs. Holley and others sell carbs for what you are trying to do. The single carb top could have distribution issues, but not always. If you could borrow a carb, it is worth a try. JMO.
 
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