Cam Duration

Chuckster88 · Mar 30, 2005

When you get a cam with a lot of duration does that make it lope or is it the lift? Is it better to have a lot of duration or less or a lot of lift? What is a 3 angle valve job?

UltimateWarrior · Mar 30, 2005

Chuckster88 said:
When you get a cam with a lot of duration does that make it lope or is it the lift? Is it better to have a lot of duration or less or a lot of lift? What is a 3 angle valve job?

Having valve overlap is what gives you a lope. The intake and exhaust valves are open at the same time for a split second as the intake is opening and exhaust is closing. What cam profile is best is based on application: street car, drag car, road racer, ect.

da zman · Mar 30, 2005

Chuckster88 said:
When you get a cam with a lot of duration does that make it lope or is it the lift? Is it better to have a lot of duration or less or a lot of lift? What is a 3 angle valve job?

lope is determined by this formula

intake duration + exhaust duration / 4 - lsa x 2

this is how you find degrees overlap hence lope

mike

CanadaStang · Mar 30, 2005

Here is some good info for ya:

http://www.hotrod.com/techarticles/113_9604_cam/

Gearbanger 101 · Mar 30, 2005

UltimateWarrior said:
3 angle valve job is when you have 3 flat surfaces on heads of the valves that are at different angles from the stem of the valve instead of just one seating surface you have 3 individual ones.

That is incorrect. The different angles are ground into the valve seat, not the valve face itself.

Ex....the typical 45-deg cut on the valve.

....followed by the multi-angle cut on the valve seat located within the combustion chamber.

Illustration below....

CanadaStang · Mar 30, 2005

Yup, what he said ^
[nice illustration by the way ]

mogs01gt · Mar 31, 2005

Brian, where did you find that diagram of the multi-angle vavle job? That is pretty slickl.

Gearbanger 101 · Mar 31, 2005

Sorry guys, I went off-line last night, shortly after I posted that. Thanks for the props CanadaStang....and as for where I got it, I'll do you one better Mogs and post the link to the entire article.

http://www.automotiverebuilder.com/ar/ar119854.htm

....ignore the fact that it's a Chevy head that their doing the valve job on.

Cam Duration

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