adjusting cams was Re: [Shotimes] Help with engine stumble
in 95 MTX
Ian Fisher
dataflash@yahoo.com
Wed, 10 Aug 2005 17:07:20 -0700 (PDT)
So if I advanced the exhaust cam and/or retarded the
intake cam, I would be decreasing overlap?
Ian
--- Jim & Debbie Leyden <jndleyden@comcast.net> wrote:
> Ian,
>
> The correct sequence of a four stroke cycle engine
> is Intake, Compression,
> Power (or expansion) and Exhaust, then start over.
> So in reality, the
> intake follows the exhaust. Therefore, in order to
> increase overlap, you
> would retard the exhaust cam (keeps it open later)
> and advance the intake
> cam (opens it sooner). Three degrees sounds close
> and it can be done
> without the adjustable sprockets.
>
> Jim
>
>
>
> -----Original Message-----
> From: shotimes-admin@autox.team.net
> [mailto:shotimes-admin@autox.team.net]
> On Behalf Of Ian Fisher
> Sent: Wednesday, August 10, 2005 3:28 PM
> To: Zach Leahy; George Fourchy
> Cc: shotimes@autox.team.net
> Subject: adjusting cams was Re: [Shotimes] Help with
> engine stumble in 95
> MTX
>
> Interestingly enough, a lot of people I have spoken
> to
> have (or plan on) retarding their exhaust cams 3
> degrees to dial out overlap when using reground
> cams.
>
> On the other hand, Lance Cheney has his exhaust cam
> advanced 3 degrees to dial out overlap. Technically,
> this seems to make more sense, right?
>
> Intake valves open first followed by the exhaust. If
> the exhaust cams are advanced 3 degrees, they'll
> close
> sooner and spend less time open while the intake
> valves are open. Does this make sense?
>
> I am not going to install my +20's straight up. I
> plan
> on either advancing or retarding them 3 degrees to
> start with. I just need to figure out which way to
> go.
> I know that at 0 degrees of adjustment, there is too
> much overlap so I'm not even going to bother with
> that
> setting.
>
> Ian
> --- Zach Leahy <leahyz@gmail.com> wrote:
>
> > Yes George, that's what I did, in a couple
> > positions. What the
> > previous post was saying is that you are retarding
> > or advancing the
> > entire valvetrain, intake and exhause when you
> move
> > one tooth on the
> > belt.
> >
> > To actually be able to change just the intake, you
> > need to move the
> > intake one way nad then correspondingly move the
> > exhaust (chains) the
> > other way. That would allow you to adavance the
> > inake perhaps and
> > retard the exhaust, decreasing overlap, or
> opposite
> > to add overlap, or
> > advande everything forward, or back. Becasue the
> > intake and exhaust
> > cam are chaned together in order to change just
> the
> > intake, one needs
> > to adjust 4 sprockets.
> >
> > Z
> >
> > On 8/10/05, George Fourchy <krazgeo@comcast.net>
> > wrote:
> > > On Wed, 10 Aug 2005 08:58:39 -0700 (PDT), Ian
> > Fisher wrote:
> > >
> > > >On the SHO, the intake cams can only be
> adjusted
> > > >independently using adjustable sprockets such
> as
> > > >Josh's timing chain sprockets.
> > >
> > > Theoretically, if someone wanted to spend a
> bunch
> > of money to buy those sprockets, I
> > > suppose one could.
> > >
> > > But if you divide the number of teeth in the
> > factory sprockets by 360, you'll get
> > > the number of degrees either side of TDC one
> tooth
> > will give. I don't have any
> > > right here...they are in storage, but if there
> > were 90 teeth, each one would be 4
> > > degrees. If there were 60 (probably closer to
> > correct), then each would be 6
> > > degrees. If the crank sprocket has 30, then
> each
> > one would be 12, probably a bit
> > > much for a slight valve timing exercise.
> > >
> > > ...that sounds about right....30 teeth on the
> > small sprocket, and twice as much for
> > > half the speed...60 on the bigger sprocket.....
> > >
> > > Count the teeth, then adjust the cam sprockets
> by
> > as many degrees as you want to
> > > try.
> > >
> > > George
> > > _______________________________________________
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