just a cruiser for the street that being said im looking to get under 6 seconds 0-60MPH which can beat most vehicles on the road
#1) you don't need 400hp to do this
#2) 400hp and 3.91s does not a good cruiser make
you can do sub 6 seconds with 330hp, and 3.23s, and a 223* cam.
3.23s will get you 60= 6000 in first gear, with 28" tires and 5% TC slip.
6000 with a 223*cam is a bit of a stretch, but you will get to 60 in under 6.0 seconds with it.
You can do it with 2.94s for 60=5600 with 27" tires and a 223* cam, but you will need more than factory stall, and traction. If you burn up 2.5 seconds just to get moving, well yur gonna have to really hustle after that. And the nice thing about 2.94s is; 60mph =2200 cruising at zero-slip.
A 400 hp 360 is likely to burn the tires all the way to 60, and spinning ain't winning. And just try and get fuel economy at 60=2900 @zeroslip with 3.91s;
Now; 32 mph with 3.91s is pushing 4250 in first at WOT, and 2250 cruising in second.. That looks pretty sweet. But on the downshift, at WOT, the tires will light up, and you will have to
shift at about 44 mph. And when you do, the Rs will fall to 3250, and the power is gonna drop like a rock ................ just when you need it the most.
With 3.23s; 32mph becomes 3150 at WOT, in first gear, and
44 will be 4300 now, which is just after peak torque, so the engine is cooking! Yes, sometimes less is more. So with this combo, you will have less problems with wheelspin, and don't need monster tires.
Here's the deal ;
to hit 60mph at 5600 requires a gear ratio of ~7.15 with 27" tires.
The engine doesn't care how you get it. It could be with 3.91s and a trans ratio of 1.83.. Or it could be with 3.23s and a trans ratio of 2.21s.. Or 2.94s and a trans ratio of
2.43.
Of these, only the 3.23s and 2.94s can be controlled with TC-stall speed to not go up in tiresmoke off the line. The 3.91s even at 330 hp are gonna smoke the street tires, most if not all the way to 60mph.
And the good news is a 330hp 360 practically builds itself. And with the 2.94s and a 223* cam, you might get deep into the teens or early 20s mpg from point to point.
I'm assuming your F body scales normally at 3450 to 3600; you in it.The downside to 2.94s is a bit of sluggishness in first gear, at Part throttle, with too low a stall. You can get some of that back with a slightly higher stall, more cylinder pressure, a DP carb,or possibly a better head; in other words; careful selection of parts, biased for torque..