272, 276 cams

[John Larson]

"Lift" is the height of the cam lobe relative to the base circle, how much
valve movement (at the cam) you get, either directly or through rocker arms
(which may have a ratio involved).  "Duration" is the number of degrees
during which the valve is open, and "overlap" is the number of degrees
during which the intake and exhaust valves are concurrently open.  Higher
lift implies greater cylinder filling over the same time, but that also
depends on the ability of the intake tract to fill the need, and the exhaust
tract to remove the spent fuel/air mixture.  It gets complicated from here.
The terms "advance" and "retard" have to do with the beginning of the spark
event with regard to crankshaft rotation, measured in degrees.  HTH, John
----- Original Message ----- 
From: "Tessie McMillan" <tessmc at drizzle.com>
To: "CS_Rally" <cs at csrally.com>; <jeg1976 at yahoo.com>;
<j.d.larson at verizon.net>; "Hoffman Anthony J A1C 552 CMS/MXMVC"
<Anthony.Hoffman at tinker.af.mil>; <Bluemaxww1 at aol.com>; "Alan Pritchard"
<apritchard at seaeye.com>
Cc: <quattro at audifans.com>
Sent: Friday, July 16, 2004 9:28 AM
Subject: Re: 272, 276 cams


> OK, so you remind me I had another dumb question. Pardon my technical
> inexpertise, but what is "overlap", and what is "advance"? I'm guessing
> at least the latter might be related to timing, but I don't really know.
>
> If I put in a .... higher lift, right? ... cam, what am I doing to improve
> the performance? Do I take more advantage of combustion/compression in the
> pistons, and why? Would I need to run a specific octane gas?
>
> Tess
>
> On Fri, 16 Jul 2004, CS_Rally (Carlos) wrote:
>
> > I have a 272 installed in a modified NF code engine that I'm about to go
> > through inspection and I'm also curious to see the results.
> > As Jim's car, mine is not exactly a standard NA car, but it might be
close
> > to your case. BTW, I'm running 30 degrees of advance with no idle
control.
> > I also have collecting dust in my garage a 276 that I plan to install
after
> > the smog test.
>
>
>