How does a cams LSA affect idle?

nickthegenius

Active Member

Dec 23, 2002

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Elwood, IN

Feb 21, 2004

#1

• Feb 21, 2004

• #1

I can't remember how it works. Does a tighter or looser lobe seperation angle make for a choppier idle?

 

8

8yourZ06

New Member

Feb 16, 2004

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Feb 21, 2004

#2

• Feb 21, 2004

• #2

nickthegenius said:

I can't remember how it works. Does a tighter or looser lobe seperation angle make for a choppier idle?

Click to expand...

basically..the more valve overlap you have the choppier the idle

 

nickthegenius

Active Member

Dec 23, 2002

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Elwood, IN

Feb 22, 2004

#3

• Feb 22, 2004

• #3

Ah...the overlap. I was thinking that LSA played a role in it, too. Reason I was asking is that I noticed that VT Engines has like a 108* LSA and my Comps are 113* and just got me thinking.

 

Ottomatic

Founding Member

Nov 4, 2001

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Southern IL

Feb 22, 2004

#4

• Feb 22, 2004

• #4

Valve overlap can be calculated by adding intake and exhaust advertised duration, dividing that by four, then subtracting the LSA. So LSA DOES play a huge role in the idle quality of a cam. Make sure you use advertised duration, not @.05"!

Hope this helps.

 

Ottomatic

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Nov 4, 2001

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Southern IL

Feb 22, 2004

#5

• Feb 22, 2004

• #5

Bah, forgot to mention, after you subtract the LSA, multiply the number by two and that gives the degrees of overlap.