Any hints on tuning for a big cam?

[Tom Hussey]

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.

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. 

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