my 4.1 goes like a stock 4.5 TBI
I advanced timing to 13 degrees, did all performance MSD igniton (not the box), i use AMSoil 15w40 full synthetic oil, removed heating grids in throttle body, i use premium gas (91 octane), and i changed intake to a better flowing one than stock. My 87 deville FWD goes pretty damn quick off the line.
Automobile(s): '91 Sedan DeVille Silhouette Special
High Point, NC
Re: 83 Deville Performance?
The cheapest way is to advance the timing, of course that requires 93 octane.
On 4.9's (not sure of 4.1's, but I imagine it's the same) the intake and exhaust are bottlenecks for airflow. On top of that, so are the intake manifold and stock ports on the heads, but that's $$ to do. Replacing an intake isn't difficult, you just need to find one to fit it. Exhaust, just put on a straight through fiberglass filled muffler. Do not get flowmaster if you want performance, as they're not much better (if at all, in some instances) than stock.