At 09:32 PM 12/21/2004, you wrote:
...
> If converting over to a mechanical/vacuum advance setup is desireable,
> what would be the easiest (i.e. cheapest) way? The rest of my ignition
> system is stock. Thanks again, as always, for any input.
>Tod
I think the cheapest way to do this is to use a early distributor, but it's
not necessarily the optimal cost benefit solution. For a cast iron flat
tappet cam, I much prefer an early eighties distributor with the cast iron
gear and the Ford magnetic coil circuitry. This distributor will drive
most Mk IV Ford modules or all aftermarket modules such as MSD. It is
important to be able to control the limits of the vacuum advance to
optimize it. The OEM and most replacement vacuum modules are either not
adjustable or they use increasing internal spring tension to limit
advance. This is not the best way to limit the advance. Crane (and
perhaps other aftermarket MFG not known to me) build a vacuum module that
has mechanical stops to limit the vacuum advance.
The objective here is to have a distributor that is set to an initial
timing setting that is as high as practical, advances mechanically rather
quickly to a maximum of 34 to 36 degrees. These timing settings vary and
are typically a function of the cam and compression you are
running. Higher performance engines normally respond better to high
initial and lower maximum settings. Once this part of the distributor is
functioning correctly, it's time to add vacuum advance. I allow the full
timing on my mild 302 to run to about 44 degrees under no load, cruise or
light load conditions. A good timing light is essential in this process.
My 302 with a mild Ford roller cam, 1.7 roller tip rockers, 550 CFM Holley,
2.88 posi, 5speed, no mechanical fan, and 205-13 tires routinely gets 25-26
MPG at freeway speeds of 70MPH at just about 2000 RPM. It's certainly no
slouch performance wise and it's lots of fun going on trips with other
Tigers and filling up every other time they do. But you do have to
understand that cheap is not always optimum.
Tom
|