I have a non-smog (7.5 x 2 = 15 degree) distributor. So you are saying that
if I use my timing light to look at the marks on the pully, the following
should happen:
1) I should adj distributor rotation at low rpm to see 16 degrees (or
whatever for your engine) of advance on the marks. I have a '70 1600 so I
will see the 4th mark (3rd mark from the big zero mark) line up with the
pointer (or just past the 4th mark since each mark is 5 degrees).
2) Then when I rev up the engine, I should see another 15 degrees of
advance, or the rotation of the pully should move past the 5th (final) mark,
which would be 5 degrees more, then another 2 more "mark's worth" of
rotation for a total of 15 degrees more of advance -- due to the engine's
rmp increase beyond the idle setting.
3) And all of this is with the vacuum connection DISCONNECTED.
RIGHT or WRONG?
With my present setup, I see only about 10 degrees of additional rotation
after the idle setting when I rev up the engine. So is my distributor not
advancing correctly (not giving me 15 degrees more as it revs up, but only
10), or does the other 5 degrees come from the vacuum advance which is not
hooked up???
It hasn't been clear to me that the 15 degrees of advance for a 7.5
distributor means that this 15 degrees is ALL due to the mechanical advance.
Could it be that part of the expected 15 degree additional advance is
supposed to come from the vacuum mechanism?
Has anyone actually seen a full 15 degrees of additional advance when the
rev their engine past idle (and has the vacuum advance not hooked up)???
Hope you are not sick of this distributor thread, but I want to know if my
distributor needs replacing. I did carefully rebuild it so it all works well
again, but maybe didn't do it well enough.
Bob Wilson
1970 1600 (stroker now) 28383
On my set
-----Original Message-----
From: Brian Hollands [mailto:bholland@hayes.ds.adp.com]
Sent: Wednesday, April 04, 2001 5:50 PM
To: Datsun Roadster Mailing list
Subject: RE: vacuum advance
Only other thing to note is that if you have the smog distributor, you can
rebuild it with the proper 7.5 degree distributor cam. Several places used
to sell the "distributor recurve" kits to do this. If these aren't
available anymore due the extreme environmental catastrophe that their use
invites, I would think that you could weld and recut the slots in the cam's
base plate to alter the total amount of mechanical advance. I don't
remember as I recurved my dist. years ago - do the two versions use
different weights and springs? I think I remember replacing the springs but
I don't remember if that was necessary or just a good idea.
Fairlady sells an electronic distributor also. Anyone got any experience
with that?
Brian
A smog distributor is 15 degrees cam, 30 degrees crank. 30-30=0.
Yup: smog cars get set 0 BTDC which is why off-the-line performance
sucks, errr, I mean, is poor. Give it a few degrees advance and it'll
run MUCH better. It'll also melt a piston pulling a hill :-(.
p.s. When you take apart the distributor, the advance plate will
have either a 7.5 or a 15 stamped on it. Now you know what that
number means!
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