05-24-2021, 10:17 PM | #1 |
Drives: 2017 Chevy Camaro 2SS "Fifty" Join Date: Aug 2020
Location: AL
Posts: 13
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Probably a dumb question about cams but I'm gonna ask anyways...
This is driving me nuts. I've been reading up and watching videos about camshaft dimensions, what the various measurements represent, etc. I understand there can be arguments about what is the "best"...whatever. here is my question...in some of the descriptions for cams I've seen, the lobe separation angle is something like "114+5"...I get the LSA 114 but what does that +5 mean?
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05-25-2021, 08:12 AM | #2 |
Drives: Camaro 1SS Join Date: Jun 2020
Location: PA
Posts: 82
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You are asking about CAM Advancing / Retarding.
https://help.summitracing.com/app/an...t%20centerline. |
05-25-2021, 08:26 AM | #3 |
Drives: 2019 Camaro 2SS Join Date: Aug 2020
Location: McCordsville, Indiana
Posts: 621
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Exactly that cam for instance would have a 114 deg lsa with 5 deg of advance ground in.
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05-25-2021, 08:32 AM | #4 |
Drives: 2016 1SS NFG A8 Join Date: Aug 2017
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The +5 degrees of advance built in is to help maintain good off idle throttle and mid range power. Hence why GM uses VVT. They advance the cam down low for max torque, then retard it up top for max power. Since it's best to lock out VVT with most aftermarket cams, you have to settle for a "middle ground" per say and a lot of cams will have some advance ground in them.
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05-25-2021, 08:57 AM | #5 |
Drives: 2017 Chevy Camaro 2SS "Fifty" Join Date: Aug 2020
Location: AL
Posts: 13
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So in short, it means the mean LSA would be 114° with a 5° advance ground in. So why don't they just say that the LSA is 119°? Or is the +5° advance ground into the intake valve lobes only?
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05-25-2021, 10:27 AM | #6 |
Drives: 6th gen Join Date: Aug 2013
Location: US
Posts: 3,664
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LSA and cam advance are two different things.
The LSA is the separation between the intake and exhaust lobe, that’s really ground into the cam and the advance is how you’re clocking the cam, you can change this with an adjustable timing gear if u wanted. That’s why the nomenclature needs to stay 114+5 Then you get an idea of your icl
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05-25-2021, 10:49 AM | #7 | |
Drives: 2017 Chevy Camaro 2SS "Fifty" Join Date: Aug 2020
Location: AL
Posts: 13
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Quote:
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05-29-2021, 12:02 AM | #8 |
Drives: 17 2SS, 8L90, Cam, Heads, E85 Join Date: Dec 2016
Location: US
Posts: 1,196
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What I've never understood is where is the true "zero" or reference on a cam. There has got to be a reason they advertise the advance as a certain number rather than bake it into the cam specs.
So for example if you can use the intake and exhaust duration, LSA, lift, and ICL to completely determine a graph of the cam timing and give you all 4 valve events, then why can't the + advance number just be "baked" into the cam specs? |
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