We need more info about your engine. Is it a healthy running engine that you want to upgrade? Or worn out and needs to be rebuilt? What style of Jasper rebuild, stock, or one of Jasper's hi-performance builds? If it's worn out, as pointed out, you could spend $1000 just on machine work to do a quality rebuild, with no way to do a performance build for that sum. However, if you have a solid, healthy engine, you could do some upgrades for $1000 that would enhance the performance, but reaching 400 hp for that price probably is an unrealistic goal.I do not know to much about cars but I do have a 81 chevy camaro with a rebuilt jasper 350 in it and that is all I know. How would I go about getting it to 400hp with about a thousand dollar budget.