Ignition Timing adjstemnt For H-iCompression

First I make sure my linkage behind the engine is not bent. I want both levers to work correctly. I run a 6.0 head. I set the timing 1 notch down. When taking off, my foot goes to 1/2 throttle, then I pull the spark down and feel the engine start pulling good, when the engine starts to fall over/ stops pulling I back off the timing just a touch.
I was tought at age 13 how to set the timing by ear and feel on tractors and cars. This is one of the reasons I love the model A.
 
Synchro, thanks, wear and tear on the used B distributor is a good reason to try something else. You are right those numbers mean nothing to me but I did find the Lucas 25D is a straightforward conversion with both mechanical and vacuum advance and retard.
 
David in San, where your lever ends up depends entirely how your rotor is positioned at tdc. Advancing or retarding the position of the rotor changes where the sweet spot is on the lever. Most common is that with the lever fully up for starting the timing is slightly retarded, 0 to 10 degrees, when started and pulling the lever down and finding the sweet spot at whatever speed you are running determined where the lever ends up. Advanced timing could be anywhere from 20 to 30 degrees depending on the initial setting of the rotor position.
 
Bob Bidonde said:
I have a 6:1 cylinder head on my engine, so I can only use the first 3 notches on the spark lever. The 3rd notch is for 30+ MPH speeds to avoid spark knock. I need to be able to retard the spark somewhat to fully appreciate the hi-compression head. My thought is to time the ignition at TDC of compression of Cylinder 1 with spark lever down 4 notches. This should give me 4 notches of lever travel up to retard the spark to occur at about 13 crankshaft degrees max.
What are your thoughts about my plan?
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Bob there’s 5 different timing covers ! 1928 - 1934 , there are advanced timing pin holes ! Could your cover be one of the advanced covers ?
 
In several years of reading this forum this is the first mention I have seen about vacuum advance. I have recently wondered why that feature isn't used more often. It would seem to be easier than installing the mechanical advance in the valve chamber, and there are probably several salvage yard distributors that could be adapted for A use.
 
Russell Reay said:
In several years of reading this forum this is the first mention I have seen about vacuum advance. I have recently wondered why that feature isn't used more often. It would seem to be easier than installing the mechanical advance in the valve chamber, and there are probably several salvage yard distributors that could be adapted for A use.
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But would the advance curve be correct for a Model A? A distributor designed for an engine spinning 6000rpm is going to work do well in a Model A engine turning ~2000rpm without a certain amount of rework.
 
Y-Blockhead said:
But would the advance curve be correct for a Model A? A distributor designed for an engine spinning 6000rpm is going to work do well in a Model A engine turning ~2000rpm without a certain amount of rework.
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Yes, centrifugal bobweight springs perhaps even the bobweights themselves would need to be altered to suit the ~2000 rpm Model A engine. Vacuum advance canister would need adjusting to suit as well.

Access to a distributor machine would be useful for this procedure. One could possibly do it with a timing light providing the crankshaft pulley is properly marked but would be cumbersome to make the adjustments in this way.

I have a 1970’s Honda points distributor with centrifugal and vacuum advance on my “B” engined 1930 sport coupe. Used a home built distributor machine to dial mine in. Works great. :)
 
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[QUOTE I have a 1970’s Honda points distributor with vacuum advance on my “B” engined 1930 sport coupe. Used a home built distributor machine to dial mine in. Works great. :)[/QUOTE]


I am just about to install a "B" engine into my 1930 sports coupe .Can you go into more detail as to what Honda dis you used ect.


thanks in advance
 
The best would be a combination of centrifugal and vacuum advance. The centrifugal is needed to retard the ignition for starting and to advance it for different rpm's. The vacuum advance is useful to slightly retard the ignition when the throttle is open more, like going up a grade or accelerating.
 
For me nkaminar has got it right. I have thought about this a lot and felt the combination of centrifugal advance with a vacuum component would be suitable for a model A particularly heavier model As like Briggs and murrays.not being able to see what is going on in the distributor was driving me nuts so the search for a sun machine began. The machine I found was used hard and put away in a trailer not to far from the ocean so it was a rusted hulk. Anyway after bringing that back from the dead and reading what some other folks had done I decided the Lucas 25D would be suitable. Used in many British cars of the 60s. Conventional points, centrifugal advance, with vacuum advance which I see as an automatic retard under load. The short story is the centrifugal advance works in the model A rpm range but can be modified with different springs. The vacuum advance I limited to about 3 degrees total movement. My thinking at cruising speed and light load the vacuum advance adds to the total advance but under load drops back that same amount. Tested on my Burtz it did work well. As far as total advance with the 6 to one head I have my total advance around 22-23 degrees at 2200 rpm. My Burtz is in a coupe which is fairly light. I am running a single point Mallory right now but in a heavy sedan I think the 25D would be a good choice. As a heads up I bought a Chinese copy on Amazon, piece of junk. Best to find a real one if you are going to experiment.
 
headonz said:
[QUOTE I am just about to install a "B" engine into my 1930 sports coupe .Can you go into more detail as to what Honda dis you used ect. thanks in advance
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Used 1975 Honda Civic points distributor with both centrifugal and vacuum advance. Note: These are getting harder to find and as a result are getting pricier.

If I were to do this today, I would go the route Richard Knight has gone with the Lucas 25D distributor. As Richard pointed out, the Chinese knock off 25D’s may be of questionable quality.
 
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your engine needs 5-15 degrees of initial advance and a maximum of probably 26-28 degrees.
The way to get best performance is with a centrifugal advance distributor. I;m running the Mean's super B+.
 
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