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After just reading this...

http://www.allfordmustangs.com/forums/classic-tech/179249-replacing-289-2b-carb-4b-carb.html and the info that Veronica gave..."Hello. :) Don't feel bad. Many, many people think that a bigger carb is automatically better. I ran a little hands-on test on a K code that I used to have. I put a 600cfm Holley on it and drove it around, flogged it, etc... for a while, and then I put a 480cfm Autolite carb on it and didn't change anything else, and it ran better with the 480. I realize that 'runs better' is kind of vague, so, to dial that in a little better, the car was quicker off the line, more responsive, and got better gas mileage. It ran just fine with 600, but, it was almost like efi with the 480 as far as throttle response."



I am seriously wondering if all of this talk about me finding the right cam and/or heads is all a waste of time and money.(if it is, i seriously appologize to all who spent time fooling around with an issue that is my own fault) The first thing i did when i got that car was put a bigger carb and matching intake manifold on it. Now, i am worried i wasted money and its the reason im not happy with my performance. I am using a Performer 600cfm carb with basicaly a stock 2v engine aside form mods listed in my signature below. Perhaps a 500cfm Performer would have been better and i would get more performance out of it? But now with wanting a performance cam is what i have ok or should i have still went with a 500cfm instead? oh man...
 

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I think that you are overly concerned with having a carb that is too large. With the additions that you have and are planning for your engine, a little carb and timing advance tuning should result in a very good throttle response and an engine that isn't going to run out of breath when the RPMs start to climb.

There's a good many, including myself, that are using 600 CFM carbs on their mildly modified 289/302 engines with very good results. Perhaps the rear axle ratio is in need of a little lower (Higher Numerically) gear. This is definitely a way to increase your car's ability to get moving. Usually automatic transmission equipped Mustangs were originally geared pretty high. A 2.79:1 ratio differential is very usual. This is excellent for fuel economy and highway use, but will make the car a slug off of the line. If you go to lower gears, (No lower than 3.50:1 with a three speed automatic.), you will experience a definite difference in the response. If you plan on some highway driving, then go a bit higher such as 3.25:1.
 
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