Any hints on tuning for a big cam?

[Clive Apps Techno-Logicals 416 510 0020]

> 
> I am no expert on this but having a big cam, lots of overlap, long
> duration and advance should affect several parameters at low RPM.
> 
> First up the map will read high as the vacuum gets killed. The table
> there would be sure to need adjustment.

definitely
if you use TPS and RPM ignoring MAP you may be able to do better
> 
> I think it might need to idle out of closed loop because the O2 sensor
> will see some of the incoming charge that is directly pulled from the
> cyl during overlap. 

if you could control the actual time of injection
you could inject the fuel just after the ex closes and stop soon enough
that there would not be a lot of fuel pushed back into the intake
before the valve closes
this would produce a slightly stratified charge until the compresssion
mixed the soup on the upstroke

would help with both idle quality and emissions
>
Clive 
 
> You are sure to want changes to the spark advance table. Cam advance
> will reduce the volume to compress at low speeds because of duration. A
> big cam looks to close the intake well after BDC to make use of the
> pulse of moving air in the ports. At low RPM this may even back up. Too
> much advance and the cyl will misfire because of low compression.
> 
> Why not find someone with a Holley system and read the manual. They if
> anyone should suggest some ideas.
> 
> Cheers,
> Tom
> 
> Roger Heflin wrote:
> > 
> > Bruce Plecan wrote:
> > >
> > > -----Original Message-----
> > > From: Roger Heflin <rah at horizon.hit.net>
> > > To: GMECM <gmecm at efi332.eng.ohio-state.edu>
> > > Date: Saturday, February 13, 1999 7:41 PM
> > > Subject: Any hints on tuning for a big cam?
> > >
> > > I've *heard* of tinkering with the filter rates to smoothing things
> > out.
> > > Bruce
> > >
> > 
> > No idea of which parameter to try?   I am going to need to look and
> > see
> > exactly what is making it cycle, I am guessing maybe the O2 sensor has
> > a
> > filter on it, and changing it should make things better.  Time to run
> > some tests on the data I have.
> > 
> >                         Roger