Steve,
I was more like flabbergasted (or gobsmacked as the Britts are fond of
saying). When I first fired the motor I just set the advance according to
feel and how it drove. When I got around to putting the timing light on it
I had about 53 degrees at full advance. My first impression was that this
was impossible and my reading was wrong. Double checked TDC and confirmed
zero degrees on timing marks; also tried different timing lights. That was
ten years and two rebuilds ago. Since then I have gotten accustomed to this
characteristic. I attributed it to lack of turbulence due to more open
chamber and polishing, and/or lower compression than the 289 heads. Upping
the compression from 9.3 to 10.9 had no effect on the required advance,
however. Even with this much compression and advance, I've never have any
pinging using 92 octane. At open track events I've run racing gas which
feels maybe like it gives a little more power and also gives my tailpipes a
nice patina.
As for my distributer, it is entirely mechanical; it's an old model Accel
with adjustable cam, springs, and weights.
I agree that too much advance can be disastrous; burned pistons, etc. I've
always used forged pistons for a margin of safety in this regard. Hard
telling how long it might have taken me to work up to 50 degrees of advance
if I hadn't blundered into it right away. I always say, if you have the
choice of being smart or lucky, pick the latter!
>Bob,
>
>Your advance settings are a little disturbing. You should never have
>more than 36 degrees total advance, with a few exceptions.
>
>Under deceleration, or constant low-load cruise, it can go as high as 50
>degrees. But this is controlled by the vacuum-advance which cranks
>additional advance in at nearly closed throttle (High distributor port
>vacuum, not to be confused with manifold vacuum).
>
>I believe you ought to check your vacuum advance canister. My diaphragm
>was gone, and the entire system retarded my spark when set correctly at
>idle (no mechanical or vacuum advance). The engine ran retarded and
>would overheat. Don't know how you set your advance, or check it out,
>but would recommend a simple test. Remove the distributor vacuum hose
>from the carb and suck on the hose connecting to the distributor can. If
>you get air thru the hose, the vacuum diaphragm is got a leak. I
>replaced mine with an Accell unit that has an adjustable vacuum advance
>setting with an allen wrench. The kit comes with a couple of sets of
>springs to change your mechanical advance rate, if you desire. Then
>follow enclosed directions.
>
>Steve
>--
>Steve Laifman < One first kiss, >
>B9472289 < one first love, and >
> < one first win, is all >
> < you get in this life. >
>
>
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