What modifications are mainly for top end power (50MPH and so on)

for a 3.1 - 6

 

mph and 'top end power' (I assume you mean upper rpm power?) are two different things.

If you want to increase your get-up-and-go from 50mph+, then you need to look at what rpms you are at, WOT, above there - I'd say you want to increase from 3500-5500 rpm?

If so, a cam swap, headers, catback, and intake (yes, EVERYTHING is working against you, stock) will go a LONG way towards that!

 

Would just a cam work?

 

What doward said every thing would just get in the way of the cam. The exhasut manifolds, heads, intake.

 

Yeah thats the exact ranges I need the power.I was thinking the Cam from Summit for the 3.1.Its ranges 1500-4500 which is perfect.What else is needed for a cam.Modified ECU?

 

Honest
you are working with a worn out engine & wishful thinking.
STOCK set up best would be increase ignition power, exhaust flow, incoming air flow.
Stock set up, this factory MPFI bottles up at 4500 RPM.
Yes you would have to rework lots of things to make "more".
IF you are serious about this get a 3.4 mill to take advantage of extra power down below that RPM range....
BUT I can also say that at 4500 plus RPM my stuff bottle necks up, too due to stock exhaust. Most restrictive set up is the stock exhaust.
Get headers and see where stock power RPM extends and how much you retain (torque).
Go from there. Headers are easy to add. Cam requires lots of effort. IF ya do a cam ya almost 1/2 way to stripping engine bay for a 3.4 block swap boogie.....
BUT IF ya add headers, ignition, stuff like that, it all swaps over to a 3.4 mill, easy!
AND the 3.4 cam is the one you are "seeing" in that publication. Yeah stock 3.4 come with very good cam!