Stroker specific cams?

DrEamer said
As far as the EFI goes, Edelbrock recommends a minimum of 8 inches of vacuum at idle, and have a 3 settings for cam based on duration. It seems fairly forgiving to a point, but I want to keep the duration under [email protected] for good measure. I am spending some time on their forum to see what other users are running for cams.

What is interesting is Comp uses 114 lobe separation and 8 degree duration separation on the linked cam. I'm not sure if it has more to do with it being a stroker cam, or that the XFI lobes require it. The research continues.

Looking at the proFLo 4 setup instructions, I see that they have a tabulation of 'base maps' numbers. You select the base map before firing up, based on cubes, fuel pressure range, and cam duration range (mild, moderate, or race). You can look this up in the instructions. For 'race' range durations, they list idle vacuums of 5 to 12 in. So not sure how that relates to 8" minimum. So they have tried to account for use of longer duration and narrower LSA cams.

Having said that, this system uses manifold pressure as one of the primary determinants of air flow into the engine, and thus determine load. It is an indirect method..... unlike carb venturis which are actually calibrated and adjusted to real airflow, in essence making them airflow sensors(!). Lower overall MP range is gonna simply give the ECU less resolution to be able to discern as well between different airflows (loads) and so EFI operation is going to be less precise with lower LSA and more ambiguous MP. If you're working mostly at WOT, no big deal. If you are working across a wide range of loads and RPM's then it becomes different deal, and a wide LSA helps to increase the MP range and thus the ability to resolve load/airflow.

It is not a performance matter per se, but a matter of helping the EFI to better manage the AFR's and ignition timing based on the limitations of using MP are a primary determinant of load. How good bad or indifferent it may be for your intended engine use, IDK.

BTW, here is an older Pro-Flo owners manual. If you read it and look at the graphic comparison of short and long duration cams (lower or higher overlap) and how AFR and timing are set, you can get some idea of how the system changes the settings with different MP levels.
http://www.mpair.com/assets/pdf/general/v.belt.tips.pdf