Centerline
Thread Starter
1st Gear
Joined: Jan 2018
Posts: 1
Likes: 0
Centerline
Does the centerline have to do with vacuume in the engine? More or less for smother running engine. Every day streetcar. My cam 110 centerline with 240/242 donation.
Yes 110 between lobe centers and the 240/242 is the Valve duration @.050"
Would advancing help any with vacume along with Bottom end? Also possibly removing 1.6 Rockers and going back to 1.5s?
Would advancing help any with vacume along with Bottom end? Also possibly removing 1.6 Rockers and going back to 1.5s?
Last edited by Dmnin; Jan 16, 2018 at 09:46 AM. Reason: more information
Drifting
Joined: Dec 2002
Posts: 1,946
Likes: 28
From: Long Beach CA
Not sure I understand. Are you saying that your cam has 110* between lobe centers? Or are you talking about advancing or retarding the cam timing? And is the 240/242 the advertised duration or the valve duration at .050"?
Safety Car
Joined: May 2003
Posts: 4,797
Likes: 239
From: Ocean Township NJ
Idle vacuum is a direct function of valve overlap (the period of time when both intake and exhaust valves are not fully seated). Overlap increases as durations increase and/or as lobe centerlines are brought closer together (i.e: lobe center angle decreases).
Simple explanation which I hope was helpful.
Drifting
Joined: Dec 2002
Posts: 1,946
Likes: 28
From: Long Beach CA
Absoutely. The cam in my 383 stroker is 240* at .050" and it does have a rough, lopping idle and about 10-11" of vacuum at idle. But it is advertised at 270* duration. Advertised duration and duration at .050'' are normally very different things, and make a difference in vacuum and engine performance. As will lobe separation, as 65Tripleblack stated.
