Lets talk overlap and its effect on PA and NA motors
Registered User
Joined: Dec 1999
Posts: 1,697
From: Petersham, MA
Well...I'm not sure how "advanced" of an answer I can give you, but I'll give it a whirl.
Overlap is the amount of time that the intake valve and exhaust valve in the same cylinder are open at the same time. Heavy overlap is common in cams with large duration and tight lobe centers.
On a NA car, overlap is desirable as the exhaust stroke pulse helps to draw in the intake charge(remember, the intake valve is opening while the exhaust is still open). On a supercharged engine, this is not desirable as the exhaust valve opening while the intake is open allows your boost to blow right out the exhaust.
------------------
'97 Firebird Formula WS6
383 stroker, Ported/Polished heads with 2.00/1.57 valves, 1-3/4" headers, 2600 stall, blah blah blah.
Overlap is the amount of time that the intake valve and exhaust valve in the same cylinder are open at the same time. Heavy overlap is common in cams with large duration and tight lobe centers.
On a NA car, overlap is desirable as the exhaust stroke pulse helps to draw in the intake charge(remember, the intake valve is opening while the exhaust is still open). On a supercharged engine, this is not desirable as the exhaust valve opening while the intake is open allows your boost to blow right out the exhaust.
------------------
'97 Firebird Formula WS6
383 stroker, Ported/Polished heads with 2.00/1.57 valves, 1-3/4" headers, 2600 stall, blah blah blah.
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