[Puddin]

Originally Posted by DorkMissile

In general, in a N/A application you can get away with overlap, and the larger the CI the more you can get away with.

The problem is - If / When you boost it, you will then be loosing boost.

If you are boosted, and have overlap, you are blowing air & fuel right out the exhaust. It doesn't matter what you have for headers, intake, etc.... it goes out and is lost.

For my setup I was looking at a lot of cams. I was down to two or three, one had 0 overlap, one had one degree of overlap, and one had 5. All three cams had intake close points that were within one degree of each other. Between where that point is and TDC at the end of the compression stroke is your chance to build pressure. If you have overlap once the piston gets to TDC while under boost, you are reducing the amount of pressure you can generate.

The whole process of looking at duration numbers and LSA angles means nothing. You have to open and close the valves at the right time.

Unfortunately so much emphasis is put on the idle sound. Yea, 8-10 degrees of overlap will get you a lot of attention when you putt around at cars & coffee, but you are going to trade drivability and cruising power for it.

I myself worked with a cam builder that I think is the best to work with, paid the money for a custom cam, and I was floored at how small of a cam they recommended. My build is a stock cubic inch configuration with stock heads, but I am still using a Novi1500 head unit (can move 1200+cfm). Now I specifically told them I would rather have 30 more ft lbs at 6000rpm vs 30 more hp at 7000rpm, but upon talking to the tech, he said that was more overlap than anything. Keeping between -2 to 0 degrees of overlap was the best way to "get the best of both worlds"

I was referring to Cam Motions Gen 5 LT/CS 242/258 Centrifugal Supercharger Camshaft (242/258-117+4) cam when I was talking about getting away with more overlap. It has 16 degrees of overlap yet they still classify it as a Centri style blower cam for 416-427 motors. To be honest all this cam stuff confuses the hell out of me so I just told my shop/TSP to design a cam for me that would allow for boost later on.