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I currently have a 1977 Mustang II with a 302 - Automatic Trans - with a 4bbl vaccuum secondary carb. The carb is a Holley 600 cfm. I need that carb to open quicker on the four. I see the manual indicates changing the spring in the vaccuum chamber... will this work? The timing is set perfect, running dual straight 2-3/4 pipes to the axle with Flowmaster mufflers. The car is breathing but I'd like to shred the tires on the shift points with the equipment I currently have. Any tips or tweeks are welcome. Thank You in advance.
 

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Yes a lighter spring will make it open faster, but if it opens too fast, you may actually make less power. Get a few different springs and experiment until you find the one that works best for you.

Shredding your tires on the shift points is a fast way to wear out your car, so I hope you only do it when you are drag racing, unless you are really looking forward to rebuilding your transmission frequently.
 

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You'll need to change the cam to get any kind of power out of that 302, they were a dog with that retarded cam, get one from the 86. I think it was a B303
 

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this is kind of a rig but if you look on the drivers side at the throttle linkage there is a rod going from the primary linkage to the secondary shaft to prevent or limit it from opening at idle or part throttle. if you take a small machine screw with matching nut and lock washer you can strategically place it in the rod slot where it will pull the secondaries open somewhere around half throttle. this way you can see if it works better having the secondaries open earlier or not.
 
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