[T3] Kettering Ignitions (Jim Adney)

Sat Feb 13 21:36:16 PST 2021

The heads I used still had the step , the machine shop just cleaned them up
and didn't take off much. They used a fly cutter. Still the area of the
stock piston top dish does change the compression ratio, it's not all the
heads.

On Sat, Feb 13, 2021 at 5:34 PM Keith Park <topnotch at nycap.rr.com> wrote:

> Remember, CR is also a function of the heads, stock late heads were
> stepped,
> but by now most of that has been fly cut away as machine shops got a hold
> of
> them
> And wanted to "clean them up" and over all these years, perhaps multiple
> times.  Aftermarket heads are a crap shoot, unless you CC any head your
> going to use,
> And measure deck height you have no idea what the compression ratio really
> is.
>
> Keith
>
>
> Topnotch Restorations
> topnotch at nycap.rr.com
> http://www.topnotchresto.com
> 71 Squareback  “Hothe”
> 65 Notchback  “El Baja Rojo”
> 93 RX7  “Redstur”
> 13 Subaru Outback "Blendin"
>
> -----Original Message-----
> From: type3-vwtype3.org <type3-vwtype3.org-bounces at lists.vwtype3.org> On
> Behalf Of William Jahn
> Sent: Saturday, February 13, 2021 2:07 PM
> To: type3 at vwtype3.org
> Subject: Re: [T3] Kettering Ignitions (Jim Adney)
>
> To clarify : With the timing set @ 5 BTDC and the vacuum advance connected
> it will ping which it never used to. The flat top pistons increase the
> compression ratio . When I set it close to TDC without the vacuum line
> connected it felt like it had more pep. This was when I removed the
> Pertronix and put back points so I had to reset the timing. I haven't set
> it
> @ TDC and tried the advance. I'd set the timing  @ 5 BTDC and drive it no
> vacuum advance and it pinged so I backed it off to 3 BTDC and it stopped
> then I connected the vacuum line and once it was warmed up it pinged. I
> just
> left it there and plugged the vacuum line. I feel 5 BTDC is correct yet it
> does not work out well since it pings. It's either the flat top pistons or
> the fuel or a combination.
>
>  I've read you lower the RPM to 850 engine warm and set the timing . My
> mechanical advance does not kick in until over 1,000 RPM . If I recall I
> used to set it at 1,000 RPM with a timing light or just set the pointer on
> 5 BTDC then used a bulb and set it static rotating the dist till the bulb
> just came on.
>
>  Point being if your 73 is stock with the dished pistons the results would
> be different. I think that's why Russ suggested setting it @TDC , this was
> when I rebuilt this engine. Before I rebuilt the engine it had dished
> pistons and a good vacuum can and it worked fine. Since then they have
> altered the fuel we didn't have ethanol then. I see in the Bentley 7.3 and
> 7.7 compression. With  dished stock it's 7.3 don't know if the 7.7 was flat
> top they don't state this just the year.  My goal is no pinging with the
> best performance not numbers.
>
>  Before I installed the pertronix in 97 I always ran points yet got a deep
> pit that to remove it the regap worked yet part of the pit still existed ,
> I
> would need to file through the pont hard surface.
>
>  The vacuum advance didn't make any difference @ idle yet it did offer much
> better pep on light throttle. I always set the points so both surfaces were
> hitting dead center. Rather than deal with filing I just replaced them and
> timed it static and it was always dead on with a timing light check. I
> didn't have one. I borrowed one . This was why the one fellow suggested
> pertronix because every 3,000 miles it began to miss because of the pits.
> Once I replaced them it ran fine.
>
>  I wasn't until 72 5 BTDC was introduced and they had the dual can to
> retard
> the spark at idle for emissions then did away with this in 73. If I recall
> most earlier years were TDC which were on the higher compression engines
> and
> many other early 70's 1600 FI
>
> On Fri, Feb 12, 2021 at 7:06 AM Jim Adney <jadney at vwtype3.org> wrote:
>
> > On 11 Feb 2021 at 21:44, William Jahn wrote:
> >
> > >  I've never bothered to file points. Don't they have a hard coating
> > filing
> > > past that and it's pretty thin , you file through that
> >
> > There's a layer, you can see it, and it's about 1 mm thick. There's
> > plenty of material to file if you care to.
> >
> > >  The one issue is setting the timing. When I  rebuilt this engine I
> > > used flat top pistons , Russ said at one point I should set it @ TDC
> > > rather than 5 BTDC. I Always did and it was not an issue until I put
> > > the vacuum advance line back.
> >
> > IIRC, you have a Calif, X-engine, FI/AT '73, same as mine. The vacuum
> > advance should not make any difference at idle. It doesn't on mine.
> >
> > --
> > *******************************
> > Jim Adney, jadney at vwtype3.org
> > Madison, Wisconsin, USA
> > *******************************
> >
> > _______________________________________________
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