Cam specs help
Thread Starter
Teching In
Joined: Nov 2008
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Cam specs help Thanks to this forum I have learned alot about what the cam spec numbers mean. I've got a pretty good understanding of duration, lift and LSA. I'm a little fuzzy on the different lobes but am enjoying reading and learning more about it.
I have two questions:
1) can someone explain how to calculate overlap by looking at the specs?
and
2) when a cam is listed as for example a LSA of 112 +4 - what does the +4 stand for and how does that effect performance, idle, driveability, etc
Thanks for any responses.
I have two questions:
1) can someone explain how to calculate overlap by looking at the specs?
and
2) when a cam is listed as for example a LSA of 112 +4 - what does the +4 stand for and how does that effect performance, idle, driveability, etc
Thanks for any responses.
Teching In
Joined: Mar 2008
Posts: 20
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From: Pennsylvania
To calculate overlap: ((intake duration + exhaust duration) / 2) - (LSA *2)
Example for a 224/224 cam with 114 LSA:
((224 + 224) / 2) - (114*2) = -4 deg overlap @ 0.050" lift
Example for stock LS1 cam with 116 LSA:
((196 + 207) / 2) - (116*2) = -30.5 deg overlap @ 0.050" lift
Second question: +4 means 4 degrees advanced. Advancing the cam improves low and mid RPM torque but sacrifices high RPM horsepower. Retarding the cam sacrifices low and mid RPM torque but increases high RPM horsepower.
Example for a 224/224 cam with 114 LSA:
((224 + 224) / 2) - (114*2) = -4 deg overlap @ 0.050" lift
Example for stock LS1 cam with 116 LSA:
((196 + 207) / 2) - (116*2) = -30.5 deg overlap @ 0.050" lift
Second question: +4 means 4 degrees advanced. Advancing the cam improves low and mid RPM torque but sacrifices high RPM horsepower. Retarding the cam sacrifices low and mid RPM torque but increases high RPM horsepower.
Thread Starter
Teching In
Joined: Nov 2008
Posts: 14
Likes: 0
Thanks Matt - That helps a lot. I tried searching but couldn't find an explanation but figured there has to be a simple formula since I read posts where people were quoting overlap from reading cam specs.
I appreciate the input on the degreees of advance. That explains why the shop cam guru recommended a cam with +4 spec - my truck is a 4850 pound PIG and needs all the extra low ened and mid range I can find.
Thanks again
I appreciate the input on the degreees of advance. That explains why the shop cam guru recommended a cam with +4 spec - my truck is a 4850 pound PIG and needs all the extra low ened and mid range I can find.
Thanks again
