Going CAM CRAZY!!!

elmir50 · 02-07-2001, 02:01 AM

Heres the reasoning for the way lobe angles affect engine performance:

A numerically smaller angle delays the exhaust valve opening and closeing, trapping more cylinder pressure and increasing overlap, or time both valves are open. This amke use of the engines escaping exhaust gases to pull in freash charge. The negative is that as rpm increases, it takes work for the piston to push the exhaust out and some of the charge starts to fly out the exhaust port during overlap.

A numerically bigger angle will open the exhaust valve sooner, this help to blow down the cylinder quiker, and saves the piston from pushing all the exhaust(this is useful for aiding a engine that is not naturally aspirated like nitrous)Also with artificial aspiration you do not want alot of overlap, because their is more pressure in the cylinder then when naturally aspirtaed. There is a tendancy for the charge to fly back up the intake tract if the intake valve is opened to soon.

For that lumpy idle sound a cam with more overlap will give you that at the expense of street manners. I hope the info help you decide! Your best bet is to phone crane or comp cams with all the veichle info. Good luck.

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02-07-2001, 02:01 AM	#2
elmir50 Registered Member Join Date: Mar 1999 Location: Tsawwassen BC Canada Posts: 413	Heres the reasoning for the way lobe angles affect engine performance: A numerically smaller angle delays the exhaust valve opening and closeing, trapping more cylinder pressure and increasing overlap, or time both valves are open. This amke use of the engines escaping exhaust gases to pull in freash charge. The negative is that as rpm increases, it takes work for the piston to push the exhaust out and some of the charge starts to fly out the exhaust port during overlap. A numerically bigger angle will open the exhaust valve sooner, this help to blow down the cylinder quiker, and saves the piston from pushing all the exhaust(this is useful for aiding a engine that is not naturally aspirated like nitrous)Also with artificial aspiration you do not want alot of overlap, because their is more pressure in the cylinder then when naturally aspirtaed. There is a tendancy for the charge to fly back up the intake tract if the intake valve is opened to soon. For that lumpy idle sound a cam with more overlap will give you that at the expense of street manners. I hope the info help you decide! Your best bet is to phone crane or comp cams with all the veichle info. Good luck.