Hi Rick,
Distributor machines read in distributor degrees & distributor rpm. The
engine degrees & engine rpm will be double these numbers.
The specs for your distributor call for 16-21 distributor degrees at
2500 distributor rpm. Your distributor estimate is within this range.
I believe I suggested setting the advance on the engine to 36 engine
degrees at 5000 engine rpm, or something close to this, & letting the
idle & static settings fall where they may. Vacuum advance disconnected.
This could put you at a static setting (engine degrees) of around zero
to - 4 degrees, to get around 36 to 40 engine degrees, (timing light
pointed at crank pulley) at 5000 engine rpm. The 55 degrees you are
refering to must mean that you have more than zero initial advance. Or
possibly your timing light is OFF. Or even the crank pulley marks are
off. I believe that you stock pulley is 16.75" in circumference, & 21.5
degrees per inch of circumference.
This works out to 5 degrees = .232", 10 = .465", 20 = .930". 30 = 1.40".
& 40 = 1.86". measure & check these pulley marks. I put them permanently
on the pulley rim with a file & filled them with yellow paint. The zero
or tdc mark is on the inner edge of the back pulley rim & is a tiny
drilled dimple. The stationary marker is just the rather wide embossed
arrow on the timing cover. I made this more precise by putting a new
narrow pointer closer to the pulley rim. I just attached the pointer
with "JB Quick Weld". Without these changes it would be hard to tell if
you had 45 or 55 degrees with a timing light. As you know, it's pretty
hard to get a timing light on the pointer. You have to get the timing
light beam between the front of the generator pulley & the back of the
radiator & keep the light out of the fan.
Of course if you have an adjustable timing light you just need the
single original dimple on the pulley, but I would still make the pointer
modification to put it closer to the pulley. Paralax plays a large part
in accurately determining timing mark relationship with the original
arrow & dimple. I have had the "adjustable" lights give erroneous
readings & so use the previous method.
The early Hundred Fours did not specify a degree at rpm number & just
said to set timing by ear & road test.
HTH,
Dave Russell
BN2
Rick Neves _._ wrote:
> I'm still trying to sort out why I'm measuring about 55 degrees of
advance
> with the timing like. (Not a good thing according to the experts)
>
> I made a little compass gauge out of a piece of heavy paper stock. It has
> degrees marked out in 10 degree increments. Anyway I looked at the
rotor in
> the distributor and held the compass over the center and rotated the
rotor by
> hand counterclockwise and it seems to hit the stop at no more than 20
degrees.
> So I can't see how the distributor could provide more than 20 degrees
> mechanical advance.
>
> I know there is a two to one relationship between the distributor and the
> crank but I can't get my mind around the advance numbers. Does this
correspond
> to a 2 to one relationship between the advance measured on the rotor
and the
> timing light pointed at the crank pulley??
>
> So when someone says not to have more than 40 degrees of advance are they
> talking distributor advance or crank advance?
>
>
> Sincerely
>
>
> Rick Neves
> '56 BN-2
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