Joined: Nov 2016
The main thing you need to worry about with a cam and forced induction is overlap. Overlap is the period where the intake and exhaust valves are both open. During that time on an N/A car, the exhaust is already whooshing out the header as the intake starts to open. For a brief moment before the exhaust valve finishes closing, the momentum of all the gas leaving the chamber out the exhaust helps suck the intake charge into the chamber. In fact, during most of the engine's real powerband, your exhaust does most of the work, instead of the piston's downward motion on the intake stroke.
Many high performance cams increase this overlap, which means at high RPMs, this scavenging effect is enhanced, helping the chambers fill much more effectively. It is not uncommon for a highly tuned Windsor to achieve volumetric efficiency over 100% during certain RPMs. I've seen as high as 114%, N/A. That means a 5.0 is acting like it's a 5.7 liter engine being filled with 100% of the available fuel and air it can hold! Normally that is impossible without super or turbocharging, but thanks to the highly developed intakes, cams, and exhaust we've got for these motors, it happens.
However, at low engine RPMs, there's no scavenging going on. Instead, with a cam that has a lot of overlap, some of the exhaust ends up going the wrong way, fouling the intake, and you get a coughing, stuttering mean-sounding idle, along with low vacuum and poor economy.
For a supercharged car, you have pressure in the intake to shove fuel and air into the cylinders, regardless of what the exhaust is doing. If you have too much overlap, instead of efficient cylinder filling, you're actually letting some of the unburnt fuel and air sail right out the exhaust. You also don't pressurize the cylinder with a nice compressed charge to light off, because, again, the pressure went right out the exhaust header.
When you are ready to pick out a cam, it's a good idea to talk to the cam manufacturer. They will want to know things like the vehicle weight, type of transmission, what sort of fuel delivery, rear gears, engine displacement, and a whole host of other things to help you pick the right one.
In this case, going with the stock 5.0 HO cam would be far preferable to most of the 'performance' cams out there with a hairy idle, for obvious reasons.
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