Vacuum and idle characteristics of an engine:
"SMOOTH" idle is as smooth or almost as smooth as a stock OEM engine and has high manifold vacuum, 18 inches and higher. These engines work well the stock exhaust system and torque converter but all engines benefit from good headers and performance mufflers.
"MILD" idle has a little rumble and has very good manifold vacuum, 16 inches and higher. These engines also work nicely with the stock exhaust system and torque converter.
"LOPEY" idle is a well defined lope as in the lope or gallop of a horse, and will have good manifold vacuum, 14 inches and higher.This is pretty much the "Muscle Car" idle of most cars of the 1960's and 1970's. This is the largest cam recommended for the stock torque convertor.
"CHOPPY" idle is a very noticeable performance idle and will have a somewhat lower manifold vacuum, 9 to 12 inches. These engines need headers and a torque converter in the 2400 to 2800 RPM range. This is basically a rougher "Muscle Car" idle.
"ROUGH" or "RADICAL" idle is rougher than "Choppy" and is tolerated by performance type people, however most people are happier with the Lopey or Choppy idle type camshafts. With the "Rough" idle cam, the vacuum will be under 8". Also this engine will need headers and performance exhaust system. A 2800 RPM or higher torque converter is recommended. A vacuum canister or electric vacuum pump may be necessary.
Generally speaking Engine Factory provides engines in the Mild to Choppy Idle Range. These engines can be used for everyday to Show n Go Vehicles.
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