<div dir="ltr"><div>Great, thanks Dave. Your explanation is very helpful. I think I'll run out and pick up new vacuum hoses and continue to use my golf tee plug system. I will see if that makes any difference in the idle variation.<br>
<br></div>I agree with Jim that some variation is common, but the perfectionist in me knows that it holds a steady idle when all the hoses are connected and so I'm curious why it cannot do so with the hoses disconnected and plugged.<br>
<div><br><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Dec 27, 2013 at 10:47 AM, Dave Pallo <span dir="ltr"><<a href="mailto:rdavid@rochester.rr.com" target="_blank">rdavid@rochester.rr.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">[[[On the timing issue, I have a '72 and I follow the procedure in Bentley<br>
(roughly: set idle, confirm throttle is closed by pulling 1 dist. hose and<br>
observing timing mark, pull & plug both hoses, reset idle, time, re-connect<br>
hoses, reset idle). When I have both distributor hoses off to set the<br>
timing, my engine always surges a bit, so the timing mark moves. I just get<br>
it so the center of the swing is the proper timing and assume that is OK.<br>
<br>
<br>
<br>
If anybody else has a '72 out there, do you experience this similar surging<br>
at idle when both your distributor hoses are disconnected? It is maybe a<br>
swing from 820-870 (so still within the 850 +/- 50), but enough to make the<br>
timing mark move.]]]<br>
<br>
<br>
<br>
Following the Bentley timing procedure is the right thing to do. It tells<br>
you what to do (but not why), so if you follow the Bentley directions for 72<br>
- you'll time it correctly.<br>
<br>
<br>
<br>
. For a 72, it is very important that the throttle plate fully<br>
closes. This enables the vacuum retard port to have vacuum at idle (also<br>
very important). A correctly adjusted throttle valve switch will not stop<br>
the throttle plate from closing fully.<br>
<br>
. The idle speed screw does not provide a mechanical stop for the<br>
plate (as in carbed engines), but instead allows a very small amount of air<br>
into the IAD to control idle speed. This screw will not hold the throttle<br>
plate open at all.<br>
<br>
. For a '72, the vacuum retard is what pulls the points plate back<br>
AT IDLE and makes it possible to achieve the 850 rpm at idle. That is why we<br>
have vacuum retard. If you are correctly timed at 5 degrees, and your vacuum<br>
retard is not working - you more than likely won't be able to adjust the<br>
idle speed screw enough to get the idle down to 850 rpm.<br>
<br>
<br>
<br>
This are some reasons why you have to follow the Bentley. The '72 motor<br>
needs to be timed at 850 without vacuum influence, but as soon as you<br>
connect the vacuum lines; the points plate moves - and so will the timing<br>
marks, and therefore the idle speed. That's why you are going back and forth<br>
with setting idle speeds when setting the timing.<br>
<br>
<br>
<br>
The surging you are seeing is not good for timing a motor - any motor,<br>
regardless of year, FI or carbed. This is not a '72 thing. You are probably<br>
correct in looking for any vacuum leaks, as that will cause surging. It's<br>
probably not your golf tees, as we all use 'em ;-)<br>
<br>
<br>
<br>
And Thanx for the props, Bob! Experience is the best teacher, isn't it?<br>
<br>
<br>
<br>
<br>
<br>
Dave Pallo<br>
<br>
'72 Square ~ Elwood<br>
<br>
Fairport, NY<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
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