On Tue, 16 Mar 2004, SCH (OldSub) wrote:
> My motorcycle fires on every stroke, and the V-6 with three coils I used to
> have fired on every stroke, but I'm pretty sure the old six in my truck only
> fires on the compression stroke.
Sorry the 2-stroke thing had me thinking motorcycle engines again. They do
fire every stroke, so do crank driven distributors, cam driven only on the
compression. Sorry...
> I know the V-8 in my newer ('72) truck only fires on the compression stroke.
> Isn't the distributor on these old motors driven off the cam just like on
> the V-8s? Since the cam runs at half engine speed, the distributor must
> also.
>
> -----Original Message-----
> From: zman [mailto:zman@gibbon.kungfumonkey.com]
> Sent: Tuesday, March 16, 2004 10:49 AM
> To: bigfred@unm.edu
> Cc: oletrucks@autox.team.net
> Subject: Re: [oletrucks] (NON-TRUCK QUESTION).. .How ignition works?
>
>
> On Tue, 16 Mar 2004 bigfred@unm.edu wrote:
> > I thought the distributor on a 4 stroke spins at 1/2 the rate of the
> > crank since the cam gear is 2x as large as the crank gear. If the
> > distributor is spinning at 1/2 the rate of the crank, it seems like
> > there would be a spark (at a specific cylinder) every 2 rotations of
> > the crank. Where is the hole in my a**-backwords thinking?
> > This means the coil would send a spark every 1/8 of a rotation of the
> > distributor = 1/16 of a rotation of the crank (if you use my mixed up
> > reasoning above).
> > ... I now see why there is a setting for # of cylinders.
> >
> > What your saying makes sense though, because when I've got my
> > distributor in 180 degrees (like I did last month when I was putting in
> > an HEI), the motor will back fire. This means it's trying to ignite on
> > the exhaust stroke, right?
>
> Not trying to confuse anyone. But basically the spark fires every time the
> piston approaches TDC. It does this on both the compression stroke and the
> exhaust stroke. This is why you experience the backfire when you put your
> distributor in 180 degreees off. It was easier to design the iginition do
> this than to make it skip every other rotation.
>
>
--
Scott H. Zekanis
zman@kungfumonkey.com
http://www.rod-o-rama.com
http://www.thehellbenders.com
1957 Buick Riviera Hardtop (2 dr., 364" Nailhead)
1959 GMC in Chevy Sheetmetal 1/2 Ton (235" Inline 6)
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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