Last month I posted the topic "Cylinder Pressures". Just thought I would update everyone on the end results of my modifications, as they ultimately turned out great!
Here is a rehash of what I did to my bone stock 1973 4-door Grand Am (62k miles) (400-4 motor. Performance before averaged 16.78 @ 86 MPH.
Heads swapped for 1971 #96 heads.
Intake swapped for 1971 cast iron unit.
Original Q-jet prepped by THE CARB SHOP.
Ignition upgraded to HEI.
Exhaust manifolds changed to cast iron Ram Air Headers.
Exahust upgraded to 2.5" mandrel bent, X-pipe & Walker 17749 mufflers.
Cam changed to COMP CAMS XE-262.
Rockers upgraded to Magnum 1.52 roller tipped.
The rest of the drivetrain was left alone. Stock torque converter in the turbo-400. Rear Gears are 3.23, no posi.
With the XE-262 cam, the motor was a dog off the line. I checked the cylinder pressures, which were 115-120 PSI. They seemed low, which I later found out were also being effected by the near 6000' elevation I live at.
None the less I was bent on changing the camshaft, so I purchased an engine simulator, PERFORMANCE TRENDS, and began to mess around with camshaft profiles. I ultimately came up with a profile much more mild. Oregon Cams ground up the following custom camshaft, Duration: 202/208 @.50, Lift: .413, .426, Seperation: 114 degrees.
What a diffence, the Oregon ground camshaft really woke my car up! It now pulls hard off idle and still pulls to 5000 RPM. I tested the car in the 1/4 mile again. With a passenger in the car (test weight 4513 lbs), it now runs 15.49 @ 94.5 MPH. This was at an elevation of 1200 feet. That computes to 353 gross H.P. (at 1200') or 367 H.P. at sea level. Not too bad with a low compression 400 motor(8.2 to 1) running on 89 octane gas!
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