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I've heard the term, open and closed chamber heads, what exactly does that mean and what are their benifits. I've also heard the term roller cam, does it have anything to do with the bearings? Thanks Dave
 

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Open and closed chamber heads roughly correspond to differences in the combustion chamber volume. Take the 351C for example. The standard 2V head design has a large, round, open chamber which lowers the compression ratio (given the same pistons, etc.) about 1.5 points. The majority of 4V heads were built with a sort of triangular shaped chamber that is commonly referred to as a quench chamber design. Its great for performance, but terrible for emissions.

But in other engine designs, like the big block Chevy, the open chamber head is the high performance part because it solves a valve shrouding problem with the closed chamber heads. Special pistons were used to keep the compression at acceptable performance levels.

Roller cams use special lifters with actual rollers on them. The cam bearings themselves are bushing style, no matter if the cam is a roller or not.



Dave J

My wife says if I buy another Mustang, she's gonna divorce me. I'm sure gonna miss her....
 
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