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Accel distributor advance curve
#1
Hi,

as of now, I have an Accel 34000V distributor installed in my 351C-4V. I'm trying to learn about ignition timing (the general concepts are understood). Looking at the original Ford specs in the shop manual, the mechanical advance curve is 28 crankshaft degrees @ 2300 rpm.
The Accel distributors mechanical advance can be set to the required 28 degrees. However, I can't change the advance rate. The maximum advance is reached only at 2800 rpm

Will the 500 rpm difference be significant or can I ignore it?

Thank you, Manfred
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#2
The Accel distributor is set up for high performance use, with a faster curve. All advance in by 2800 RPM sounds good to me. Unless you have 2.70-3.00 differential gear it should be fine. Initial and total timing will depend on camshaft specs and compression. If it is a stock 71 M code engine, the manual calls for 6 degrees BTDC at 600 RPM. I feel it could use at least 10 degrees initial with total being about 34-36. This may help. http://www.mrgasket.com/Portals/0/downlo...34000V.pdf Let me know if you get it worked out. Chuck
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#3
ManniB;34483 Wrote:Hi,

as of now, I have an Accel 34000V distributor installed in my 351C-4V. I'm trying to learn about ignition timing (the general concepts are understood). Looking at the original Ford specs in the shop manual, the mechanical advance curve is 28 crankshaft degrees @ 2300 rpm.
The Accel distributors mechanical advance can be set to the required 28 degrees. However, I can't change the advance rate. The maximum advance is reached only at 2800 rpm

Will the 500 rpm difference be significant or can I ignore it?

Thank you, Manfred

Since the crank turns two times for every turn of the camshaft, wouldn't that be 14 degrees in the distributor? This is not a rhetorical question. I am trying to wrap my brain around it right now myself.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
  Reply
#4
TommyK;34498 Wrote:Since the crank turns two times for every turn of the camshaft, wouldn't that be 14 degrees in the distributor? This is not a rhetorical question. I am trying to wrap my brain around it right now myself.

Yes, I understand the same as you. 28 crankshaft degrees would be 14 camshaft or distributor degrees.

- Manfred
c9zx;34494 Wrote:The Accel distributor is set up for high performance use, with a faster curve. All advance in by 2800 RPM sounds good to me. Unless you have 2.70-3.00 differential gear it should be fine. Initial and total timing will depend on camshaft specs and compression. If it is a stock 71 M code engine, the manual calls for 6 degrees BTDC at 600 RPM. I feel it could use at least 10 degrees initial with total being about 34-36. This may help. http://www.mrgasket.com/Portals/0/downlo...34000V.pdf Let me know if you get it worked out. Chuck

Chuck,

My rear axle is 3.50. If I understand you right I should set initial timing to 10 degrees and the mechanical advance to 24-26 degrees (equals to 12-13 degrees at the distributor).

Isn't the Accel curve slower than what the shop manual calls for since the shop manual requires all advance in at 2300 rpm while the Accel delivers full advance only at 2800 rpm? I don't want to be a smartass, I just want to understand. Is the difference significant or can I just ignore it if I'm not performance oriented (weekend driver).

Thank you, Manfred
  Reply
#5
Sorry I wasn't clear earlier. Yes, 28 Degrees at the crank is 14 degrees at the distributor. I'm used to referencing crankshaft degrees because that is what is read with a timing light. The manual does indeed say 14 degrees (distributor) at 2300 RPM (dual diaphragm D0OF-V, carb vacuum to advance side, manifold vacuum to retard side). I was surprised. Perhaps my memory is going but, I don't remember any of them having curves that fast when measured with a timing light. You are not being a smart ass. You should question what people post especially when you have contradictory information in front of you. Never fall victim to "I read it on the internet so it must be true". The second page of the earlier Mr. Gasket link gives directions on how to adjust the rate as well as the total advance (part trial and error procedure). The total advance I gave you earlier was strictly initial plus mechanical advance because I made a wrong assumption, I assumed no vacuum advance. With the manifold vacuum single advance it will be more (how much more depends on how you adjust it) with light or no load on the engine (high manifold vacuum). Sorry for the confusion. Chuck

P.S. How is your "Chick" doing? You didn't send her to WienerWald did you?
  Reply
#6
c9zx;34535 Wrote:P.S. How is your "Chick" doing? You didn't send her to WienerWald did you?

Chick is doing fine since my wife and I are vegetarians. No Wiener Wald, no KFC.

- Manfred
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#7
I have now set the initial advance to 10 degrees and the mechanical to 24 degrees which gives me a total mechanical advance of 34 degrees. If I hook up the vacuum advance, it adds 24 degrees for a total of 34 degrees at idle. Initial, mechanical and vacuum advance add up to a maximum of 50 degrees when I rev up the engine. All degrees at the crankshaft.

Would this be correct?

Thanks, Manfred
  Reply
#8
If it doesn't ping or surge at cruise you should be good to go. If it pings you may want to look at limiting the vacuum advance. Total advance with full vacuum applied shouldn't exceed between 48 and 52 degrees but you gotta drive it and give it what it wants.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
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