[Tigers] FW: FW: The Ultimate Duraspark Distributor Timing Guide.

Mon Oct 30 13:19:14 MDT 2017

From: Jerry Mo Christopherson [mailto:JCMC2006 at suddenlink.net] 
Sent: Friday, October 27, 2017 3:42 PM
To: 'Tom Witt'
Subject: RE: [Tigers] FW: The Ultimate Duraspark Distributor Timing Guide.

Tom, you are exactly right!   He surly made a mistake by saying “up a STEEP hill”.  The idea of using a hill in this “adjustment” is only a slight hill, somewhat less than a “steep hill”.  As you are going up a hill to maintain your speed you have to increase the throttle opening thereby LOWERING the vacuum, but if it is not a “steep hill” (floored) you will not take away ALL the vacuum.  So what you COULD end up with is too much total advance  (mechanical + vacuum) thereby giving you a “ping”.  This of course is when you BACK OFF (turning counterclockwise) the amount of vacuum the can is capable of pulling. 

One of the things I learned from the techs. at the MSD SEMA booth is that engines run BEST just below the point of “ping” (detonation, rattle, knocking, whatever you want to call it) and that is “the magic of computers”, they are able to detect (“hear” via the knock sensor) the “ping” and are immediately able to back off on the timing.  They are constantly trying to give the highest advance it can, given the conditions at that particular instant.  An example of that is, one of my friends has a Buick Grand National that is warmed up a fair amount,  one day while riding with him with a laptop in my lap hooked up to his engine computer.  We were driving down an open road at a steady 70 MPH and the laptop showed 60 degrees of advance then he floored it, the advance immediately went to 8 degrees!  The knock sensor is waiting  for that approximate 6400k sound that a “ping” puts out and signals the computer to back off on the advance.  We however don’t have that precise luxury with our old systems.  However we can get close by having the mechanical advance to the point of just below the “ping”.  Ford Motorsport Techs told me 36 degrees maximum mechanical is a very good point for a stock or mild tuned engine. (some friends of mine race a “Chump Car” their 331 engine (Ford) dynoed the best power at 35 Degrees.  My Tiger has a stock bore 302 only slightly warmed up, and my initial is somewhere around 12 or 14 degrees and tops out at 36 degrees mechanical, the vacuum will go as high as 45 total degrees.  That means I have about 9 degrees of vacuum advance.

As for the light springs (Mr. Gasket 925Ds I believe) you just want to be SURE that there is enough tension, by bending the anchor tabs, on both of the springs to keep the rotor at the “start” position for whatever your idle RPM is.  Ford Motorsport told me “as soon as the rpm starts to increase you want the advance to start ALSO”.   If both springs are of equal “size” the “curve” will be a straight line, if like the original springs of different “sizes”, you’ll get a dog leg in the “curve”.

As for MSD,  great company!  Great products (I use their 6AL).  HOWEVER  you can get the SAME CURVE with the original dist.  You gain NOTHING by using their expensive distributor!  Save your money. 

I’ve seen so many MSD dists. installed and they don’t change the springs. Out of the box directly into the engine.   MSD ships their dist. with the highest tension springs they have (covering their butts I suspect).  Resulting in a very poor “curve” indeed.  The schematics on the back of their box explains it very well, but very few people understand them.

 Hope I haven’t board everyone to tears.  I can write almost as much as Dr. Mayfield.  HA!    See you in Vegas next week Dr. Mayfield.

Jerry Christopherson

9473187

TAC insp. #58

From: Tigers [mailto:tigers-bounces at autox.team.net] On Behalf Of Tom Witt via Tigers
Sent: Thursday, October 26, 2017 11:40 AM
To: Tiger Autox
Subject: Re: [Tigers] FW: The Ultimate Duraspark Distributor Timing Guide.

A rather comprehensive article though it was a bit confusing when it when it referred to  a car going up a hill and driving on a steady flat road.

“In other words this is an engine-load dependent advance. This would be a typical situation when climbing a steep hill, or driving at low rpms, light throttle, conditions. In these conditions there is high engine vacuum, so the vacuum signal applied to the diaphragm in the canister, via the hose, will cause a 'pull' effect on the arm, which moves the breaker plate and results in a timing advance.”

I’m not seeing the high vacuum stated when going up a steep hill. The throttle is likely wide open (or there about) and the result would be a drop in vacuum. And at first I thought they might be contrasting the differences, but the next sentence states “In these conditions there is high vacuum...” and that has the appearance of stating they are similar.

Step 6
install the springs from the recurve kit and bend the tabs to keep tension on both springs so the advance shaft returns to its idle position 

This (“Step 6”) to me is one of the most important reasons proper attention should be used to set up the distributor curve.  Often people will just throw in weaker springs that can create (additional) advance at idle. The end results will be an increased amount of initial advance and if compensated but reducing the initial advance then the net effect will be reduced total timing. It’s the old “dog chasing its tail.”  The spring tension needs to be set so as to not induce any advance at idle, yet not so tight it negates the effect of the weaker springs. At the least (when done “in car”) the springs should be changed with the initial advance being known and the distributor locked down. Then the spring tension adjusted until at idle the timing is back to its previous initial setting. This should also be “stepped” into so that there is enough, but minimal tension to achieve the desired results. Ideally a distributor machine would be used. While the article addresses this it seems to get somewhat lost in the article length. 

I guess this is the point where many chime in to just $pend the money and go with an M$D or similar electronic system.  But, that wasn’t the point of the article.  And some people desire the stock appearance but want to maximize their engines capability.

From: Jerry Mo Christopherson via Tigers <mailto:tigers at autox.team.net>  

Sent: Wednesday, October 25, 2017 11:53 AM

To: Tiger Autox <mailto:TIGERS at AUTOX.TEAM.NET>  

Subject: [Tigers] FW: The Ultimate Duraspark Distributor Timing Guide.

Here is an article that a lot of you know very well, BUT for those that still have questions on ignition timing this is well done.

(The Duraspark distributor is my distributor of choice).

Jerry Christopherson

9473187

TAC insp.#58  

Subject: The Ultimate Duraspark Distributor Timing Guide.

http://vb.foureyedpride.com/showthread.php?22229-The-Ultimate-Duraspark-Distributor-Timing-Guide

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