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Tuning questions, dwell, timing, SU rough idle?

To: datsun-roadsters@autox.team.net
Subject: Tuning questions, dwell, timing, SU rough idle?
From: "Ken Pearce" <ken__pearce@hotmail.com>
Date: Mon, 04 Jun 2001 13:36:17 -0500
So I bought a Sears $49 Tach and Dwell diagnostic meter to go along with my 
$79 Sears timing gun.  I'm very happy with both!  I hadn't checked my timing 
for over a year now and since my tach went out, had no idea of what RPM my 
engine was idling at.

I have a pre-smog recurved distributor in my 68-2000 and had set the timing 
to 16 degrees last year after the engine rebuild.  Yesterday, it was dead 
on, still 16 degrees at 750 rpm.

The dwell setting is at 50 but it moves around a little.  I took the 
measurement with the vacuum advance tube removed from the dist.  Is that 
correct?  Do I need to plug the hole on the dist for the vacuum adv when 
taking a dwell measurement?

The manual for the tach/dwell meter says to take a dwell reading, then rev 
the engine to about 1500 rpm and then back to idle.  It says that if the 
dwell reading varies by more then 3 degrees, then the points need replacing. 
  Now I can't figure out if they are saying to take the second dwell reading 
at 1500 rpm or after it returns to idle?  When at 1500 rpm's, the dwell 
meter is pegged and goes off scale past 90 degrees.

Points are easy to change and cheap so I'll go ahead and change out the 
current set.  I'm just looking for a little insight as to what the dwell 
readings mean.

Also, I'm using the first (lowest) mark on the crank pulley to set the 
timing.  What are the rest of the marks for?

Are SU 2000's known for their rough idle?  Seems like I heard a comment 
about that at Shasta last year about SU's "shaking you to death".  I wonder 
if I replaced the original coil with a newer higher-output model if that 
would help?

Another question, though unrelated to tuning.  I have gas pooling in the 
little dimple between #3 and #4 cylinder on the intake manifold.  I can't 
figure out where it's coming from???  Possibly the plug in the manifold 
where the smog equip used to be???  Anybody seen this before?

Thanks in advance,

Ken Pearce 68-2000
Bellingham, WA
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