I had a 72 runner 400,4 speed,had 8 3/4 rear end 3.91 sure grip,that car was fast done a lot of work to the 400back in1974.Still sort of miss that car,it was a fun car for the short time i had it.
My buddy's car was a DOG - it just always ran really weak. He owned it for about 2 years & moved from Michigan to the Chicago area - a mechanic out in Chicagoland discovered what the problem was - the T-Quad secondaries were never opening. He fixed the carb & the car was a whole 'nother car!
I bought a REALLY nice survivor '73 Cuda 340 back in 1985 that had a "built" 340 with the 202 heads, & that car was a slug. The Mopar guy I bought it from could never figure out what the problem was - he thought it was the wrong cam. One afternoon, I was tinkering with the T-Quad, & lo & behold, discovered the secondaries were not opening. I tweaked a linkage elbow on the passenger side of the carb while off the motor & bench tested it - yep with carb held level, it opened fully every time at WOT. I reinstalled it & took it for a test ride. Holy crap - totally different car! Later that week on a cruise night, I took one of the former owner's buddies for a ride - he asked what the heck I did to it? He could not believe that they missed this diagnosis for YEARS!
Fast-forward a couple of weeks and my Dad drove my car somewhere. When he came back, he asked what I had done to the carb. I explained what we had found and what we did to remedy it. 
He then proceeded to deflate my balloon and told me had purposely shortened the throttle cable adjustment just for that reason (Dad was a hotrodder from way back and had put the car together for me). He then made me go to the dealership and buy a new link. 
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