Re: 351c - how to add torque
Tri-y's help with bottom end, changing the manifold will only help produce more HP, even then i have seen standard 4 barrel 2V manifolds on motors making 400+Hp, putting a good holley 600DP will help, but the biggest difference will be if you put in a better, not bigger but better cam, the original ford cams were designed to really limit the power of the 351. advancing the cam will only pick up a couple hp at 2000, but will lose triple the amount you pickup at 5000, and will also cause detenation problems.
Best solution i can give you is to go get a Cam Dynamics cam which are cheap at around $130, and a set of lifters, there is one that is a factory 260hp cam which makes a enourmous improvement in touque, it has 484thou lift if that helps you to find, i don't know the part no. Then add extractors, carb and go get your dizzy curbed to suit and you will be pleasently surprised.
With these motors you can put in really big cams and run crane anti pump up lifters and still have good bottom end touque.
My brother and i have done many that were stock bottom ends, put the right cam, carb, dizzy curb, exhaust, correctly tuned, and gone from running 16's to early 13's. with standard converters, and 3.0 to 1 diff gears.