Don't understand cams

roccodart440 said

That's not true.

I have 2 engines, same cubic inch, same compression, same heads. One has a 104LSA and the other a 112. The other specs (lift and duration @.050) are all the same. One idles like a top fuel dragster, the other like a puppy.

The ability of it to start properly and be throttle responsive, yes, tuning has a very large part to do with that.

An email from Jim Laroy...

"The wider lobe separation angle closes the intake valve later and reduces cylinder pressure, so that is where it's detonation resistance comes from. Really wide lobe separation angles are used in boosted applications. Many later model engines use wide lobe separation angles to reduce overlap for idle quality and fuel economy.

The only reason I use a wider lobe separation angle is to smooth out the idle and increase idle vacuum. "

Click to expand...

FOR THE LAST TIME. LSA HAS VERY LITTLE EFFECT ON IDLE.




You changed the EVENTS when you moved the LSA.

When you get the EVENTS correct, you'd find out that LSA has very little to do with idle.


The biggest deal is emissions and catalytic converters. One of the best cam grinders I know cut his teeth moving the LSA .25* to see its affects on emissions. GM paid him an assload of money to learn it.


So you can keep repeating what is wrong. You'll still be wrong.



Edit: just like in the last line of the above post, the wrong LSA will kill power. Every time. That's what your guy told you. It's nothing new. GM did it 60 years ago. It was stupid then.

There is a correct LSA for every application. To open up the LSA to clean up your tune up is stupid.

Obviously, power adders require a wider LSA. So do very efficient heads. If your heads take stock rockers, you don't have an efficient head.