Model A Distributor with Centrifugal Advance

Perry said:
I have a 5.5 head, is this OK or do I need something else?
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I have a 5.5 head and Nu-Rex advance and it works no problems. I do have my advance lever set so I can retard the timing manually if I hear any knockin'.

I made a stop for the lever to limit advance per the Phillips advance instructions. http://www.fordgarage.com/pages/phillipsspark.htm Total advance is set at ~28°.
 

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Synchro909 said:
The advance built into these distributors is set for a standard engine with a standard head. We know that as compression rises, less advance is needed.
Does anybody have an idea on how much less advance is needed for a 5.5:1 head? Same question for other after market heads that are available all the way up to about 8 or 9 to 1.
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I've found advance stays the same,1 degree per 100 rpm with a 7 to 1 head,which is the upper limit for a model a head due to flow reduction. There were some problems noted by some people with the FSI advancing a little too far at peak,a few degrees over the 1 per 100 threshold..I don't find that with mine.What does happen when increasing compression is that the engines tolerance for timing deviation lessens,dont run a high compression head with manual advance. 4.2 to 1 is tolerant of timing flaw,you can set one fixed timing and drive..7 to 1 will hammer on you,with a bigger hammer than 4.2 to 1..
 
On the subject
I have found that spark plug positioning in flatheads will influence the need for less spark advance
Compression and the condition of the balance of the motor allow for more or less advance

Getting into overhead designs the advance curve will be much different

John
 
Jack Shaft said:
I've found advance stays the same,1 degree per 100 rpm with a 7 to 1 head,which is the upper limit for a model a head due to flow reduction. There were some problems noted by some people with the FSI advancing a little too far at peak,a few degrees over the 1 per 100 threshold..I don't find that with mine.What does happen when increasing compression is that the engines tolerance for timing deviation lessens,dont run a high compression head with manual advance. 4.2 to 1 is tolerant of timing flaw,you can set one fixed timing and drive..7 to 1 will hammer on you,with a bigger hammer than 4.2 to 1..
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That all makes perfect sense. My engine is at about 7.0-7.5:1. It started at 5.5:1 but the head has been off a few times and each time, I make it flat again before refitting. Over the years, the CR has crept up to what I think is the limit. I have been considering doing what you say not to do - go back to manual timing because getting it right with auto advance is too difficult without the equipment to test the dizzy.
 
Its not hard to 'farmer' map a mechanical advance distributor.On a stock model a pulley 1/4" is five degrees,pin your engine,rig a pointer and mark a line on your crank pulley..thats tdc...get a cheapie tach dwell meter and hook it to your coil,set it to 'tach' and read the 4 cylinder scale,at idle it should be 500rpm or so with your timing light your mark should be 1/4" to the right of the pointer..run idle up to 1000 rpm on your meter,your mark should be 1/2 " to the right of the pointer..basically for each 1/4 " of separation from pointer to mark as seen with the timing light is 1 degree advance per 100 rpm..give or take,farmer style..
 
Also Mallory made the 2301105 for Model A spark curve.

And 2301106 for Model B engine.

I have single point version and a dual point version of 1105.

Both of these have spring sets and user adjustable weights and stops to setup the curve and max advance.

I have a copy of instructions that explains the setup on the house computer.

NOTE I am not at the house to check the part number just now.
 
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Ruth said:
I have a 5.5 head and Nu-Rex advance and it works no problems. I do have my advance lever set so I can retard the timing manually if I hear any knockin'.

I made a stop for the lever to limit advance per the Phillips advance instructions. http://www.fordgarage.com/pages/phillipsspark.htm Total advance is set at ~28°.
Click to expand...

I also have a copy of a Winfield 7.0 head instruction sheet that shows a similar diagram to this.

The modifications to quadrant in the WINFIELD DIAGRAM are the same.
 
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Mallory distributor part numbers corrected in blue test in post #30.

Here is photo:

https://www.summitracing.com/parts/maa-2301105#overview

NOTE:

I have not been able to find the instruction sheets. Mallory has deleted them from the website. So the links that I saved are no good.

Lesson learned I will not trust saving links anymore to save information.
 

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Benson said:
I have not been able to find the instruction sheets. Mallory has deleted them from the website. So the links that I saved are no good.

Lesson learned I will not trust saving links anymore to save information.
Click to expand...

Post those old links and maybe I can find them using Internet Archive.
 
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