Camshaft timing help

[jim_howard_pdx]

I ran my Mustang up against 4 Cobra 4.6 L cars with 3.25 rear ends and T45 transmissions during this last month.

My greatest victory was 1.5 seconds and the closest Cobra running to me was .7 seconds behind. Look, that is 30 car lengths. So I would say that I do have the 400 horsepower and that my times are right on. I spun a bearing last run, and tore down the engine. When I disassembled my heads I could rattle my intake valves. The car was clearly detonating for at least 6 months. No pinging and no noise, just detonating away silently. With the zero gap piston rings and fresh valves and guides, I should be in the 13.4 arena with slicks. I am hoping to at least be in the 13.5's. Then it is time for some quicker gears.

My computer says that with 4.30 gears and a 2500 RPM stall in the C4 I should run 12.25 seconds. I think that is pretty much on target for the light cam timing that I am running. With a 540 inch lift, 255 degree cam I would certainly be in the late 11's (engine only) and in the early 11's with Nitrous.

My car is set up to corner on the autocross, not to drag. Remember this engine idles like stock. Runs around town like stock. And when you open up the secondaries, ALL HELL BREAKS LOOSE. This is a really fun street engine.

My engine is built to take nitrous, I just do not want to put the pistons through that type of abuse with a daily driven car.

My goal is to run either a Lentco AOD or a Tremec 5 speed and 3.90 gears. That should put me in the 12.3 range and I could still cruise the car when I want.

NOW for cam timing. Retarding the cam is not a racers way of killing low end torque. Think it over. On a dyno, how do we graph HP and Torque? x coord is HP/Torque, y coord is RPM. As you graph the results of the engine you end up with a bell curve. Power starts at some level, swells at maximum, and diminishes back down. When you retard or advance the cams, you are simply shifting this curve UP or DOWN the RPM range.

The simple act of advancing or retarding does not KILL OFF anything! Honda's run about 8 hp more with 2-4 degrees retard on the intake valves and straight up to 2 degrees on the exhaust. Since they are dual overhead cams you can adjust them independently to get maximum power. You can also set the cams for maximum area under the bell curve if you are on a road race course and torque out of the corners is important.

Retarding the cam does not KILL torque. It simply moves it. Now apparently NO ONE is retarding a 3/4 cam out there so I guess it is a coin toss. Try it or leave it straight up.......